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Rahimi M, Hossain F, Leahy S, Blair NP, Jiang X, Shahidi M. Inner retinal oxygen delivery and metabolism in progressive stages of diabetic retinopathy. Sci Rep 2024; 14:4414. [PMID: 38388657 PMCID: PMC10883954 DOI: 10.1038/s41598-024-54701-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 02/15/2024] [Indexed: 02/24/2024] Open
Abstract
Previous studies have reported increased retinal venous oxygen saturation and decreased retinal blood flow and oxygen metabolism in non-proliferative diabetic retinopathy (NPDR). The current study aimed to determine alterations in both inner retinal oxygen delivery (DO2) and metabolism (MO2) in proliferative DR (PDR) as well as at stages of NPDR. A total of 123 subjects participated in the study and were categorized into five groups: non-diabetic control (N = 32), diabetic with no diabetic retinopathy (NDR, N = 34), mild NPDR (N = 31), moderate to severe NPDR (N = 17), or PDR (N = 9). Multi-modal imaging was performed to measure oxygen saturation and blood flow, which were used for derivation of DO2 and MO2. There were significant associations of groups with DO2 and MO2. DO2 was lower in PDR and not significantly different in NDR and NPDR stages as compared to the non-diabetic control group. MO2 was decreased in PDR and moderate to severe NPDR as compared to the control group, and not significantly reduced in NDR and mild NPDR. The findings demonstrate reductions in both DO2 and MO2 in PDR and MO2 in moderate to severe NPDR, suggesting their potential as biomarkers for monitoring progression and treatment of DR.
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Affiliation(s)
- Mansour Rahimi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Farzana Hossain
- Department of Population and Public Health Sciences, University of Southern California, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Xuejuan Jiang
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
- Department of Population and Public Health Sciences, University of Southern California, Los Angeles, CA, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA.
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Felder AE, Rahimi M, Nankali A, Matei N, Abdolahi F, Blair NP, Shahidi M. A retinal imaging system for combined measurement of optic nerve head vascular pulsation and stimulated vasodilation in humans. Sci Rep 2023; 13:17149. [PMID: 37816947 PMCID: PMC10564928 DOI: 10.1038/s41598-023-44390-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2023] [Accepted: 10/07/2023] [Indexed: 10/12/2023] Open
Abstract
Vascular pulsation at the optic nerve head (ONH) reflects vessel properties. Reduction in the stimulated retinal vasodilatory capacity has been reported in diabetes, but its relation with vascular pulsation is unknown. Here we report a new retinal imaging system for correlative assessment of ONH vascular pulsation and stimulated retinal vasodilation. Retinal reflectance images were acquired before and during light flicker stimulation to quantify arterial and venous vasodilation (DAR, DVR) in subjects with and without diabetic retinopathy (N = 25). ONH vascular pulsation amplitude and frequency (PA, PF), were quantified by curve fitting of periodic intensity waveforms acquired in retinal vasculature (RV) and ONH tissue (ONHT) regions. The relationships between pulsation metrics, heart rate (HR), intraocular pressure (IOP), and vasodilatory responses were evaluated. Pulsation metrics were not significantly different between regions (p ≥ 0.70). In RV, inter-image variabilities of PA and PF were 10% and 6%, whereas inter-observer variabilities were 7% and 2% respectively. In both regions, PF was correlated with HR (p ≤ 0.001). PA was associated with DAR in both regions (p ≤ 0.03), but only with DVR in RV (p ≤ 0.05). Overall, ONH vascular pulsation was associated with stimulated retinal vasodilation, suggesting diabetes may have concomitant effects on retinal vasculature compliance and neurovascular coupling.
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Affiliation(s)
- Anthony E Felder
- Richard and Loan Hill Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Mansour Rahimi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Amir Nankali
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Farzan Abdolahi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA
| | - Norman P Blair
- Department Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, 90033, USA.
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Blair NP, Matei N, Leahy S, Rahimi M, Shahidi M. The accumulated oxygen deficit as an indicator of the ischemic retinal insult. Exp Eye Res 2023; 230:109439. [PMID: 36931487 PMCID: PMC10133208 DOI: 10.1016/j.exer.2023.109439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/24/2023] [Accepted: 03/13/2023] [Indexed: 03/17/2023]
Abstract
We here attempt to improve quantification of the ischemic retinal insult, that is, what is imposed on the retinal tissue by ischemia, especially in experimental models of ischemia. The ischemic retinal insult initiates the ischemic retinal injury (or outcome). Accordingly, it is reasonable to assume that the better the quantification of the insult, the better the correlation with, and thereby estimation of, the injury. The insult seldom has been quantified in terms of the relevant physiological factors, especially in connection with the rate of oxygen delivery (DO2). We here propose the accumulated oxygen deficit (AO2D) as an indicator of the ischemic retinal insult. We hypothesized that AO2D is correlated with the rate of oxygen metabolism measured 1 h after reperfusion following an episode of ischemia (MO2_1_Hr). Previously, we showed that MO2_1_Hr is related to the electroretinogram amplitude and the retinal thickness when they are measured seven days after reperfusion. We studied 27 rats, as well as 26 rats from our published data on retinal ischemia in which we had measurements of DO2 and duration of ischemia (T) of various levels and durations. We also measured DO2 in 29 rats treated with sham surgery. Ischemia was induced by either ipsilateral or bilateral common carotid artery occlusion or by ophthalmic artery occlusion, which gave a wide range of DO2. DO2 and MO2_1_Hr were evaluated based on three types of images: 1) red-free images to measure vessel diameters, 2) fluorescence images to estimate blood velocities by the displacement of intravascular fluorescent microspheres over time, and 3) phosphorescence images to quantify vascular oxygen tension from the phosphorescence lifetime of an intravascular oxygen sensitive phosphor. Loss of oxygen delivery (DO2L) was calculated as the difference between DO2 under normal/sham condition and DO2 during ischemia. AO2D, a volume of oxygen, was calculated as the product DO2L and T. Including all data, the linear relationship between AO2D and MO2_1_Hr was significant (R2 = 0.261, P = 0.0003). Limiting data to that in which T or DO2L was maximal also yielded significant relationships, and revealed that DO2L at a long duration of ischemia contributed disproportionately more than T to MO2_1_Hr. We discuss the potential of AO2D for quantifying the ischemic retinal insult, predicting the ischemic retinal injury and evaluating the likelihood of infarction.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Mansour Rahimi
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Suite 4700, Los Angeles, CA 9003, USA.
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Rahimi M, Leahy S, Matei N, Burford J, Blair NP, Shahidi M. Impairments of retinal hemodynamics and oxygen metrics in ocular hypertension-induced ischemia-reperfusion. Exp Eye Res 2022; 225:109278. [PMID: 36252653 PMCID: PMC10985794 DOI: 10.1016/j.exer.2022.109278] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/23/2022] [Accepted: 10/10/2022] [Indexed: 12/29/2022]
Abstract
Ischemia-reperfusion (I/R) is an established model for retinal neurodegeneration. However, there is limited knowledge of retinal physiological metrics and their relationships to retinal function and morphology in the I/R model. The purpose of the study was to test the hypotheses that retinal hemodynamic and oxygen metrics are impaired and associated with visual dysfunction, retinal thinning, and retinal ganglion cell (RGC) loss due to I/R injury. Intraocular pressure (IOP) was increased in one eye of 10 rats for 90 min followed by reperfusion. Fellow eyes served as controls. After one week of reperfusion, multimodal imaging was performed to quantify total retinal blood flow (TRBF) and retinal vascular oxygen contents. Retinal oxygen delivery (DO2) and metabolism (MO2) were calculated. Pattern-evoked electroretinography (PERG) and optical coherence tomography were performed to measure RGC function and retinal thicknesses, respectively. RGCs were counted from retina whole mounts. After one week of reperfusion, TRBF was lower in study eyes than in control eyes (p < 0.0003). Similarly, DO2 and MO2 were reduced in study eyes compared to control eyes (p < 0.003). PERG amplitude, TRT, IRT, ORT, and RGCs were also lower in study eyes (p ≤ 0.01). DO2 and MO2 were correlated with PERG amplitude, TRT, IRT, and ORT (r ≥ 0.6, p ≤ 0.005). The findings improve knowledge of physiological metrics affected by I/R injury and have the potential for identifying biomarkers of injury and outcomes for evaluating experimental treatments.
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Affiliation(s)
- Mansour Rahimi
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90033, USA
| | - Sophie Leahy
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90033, USA
| | - Nathanael Matei
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90033, USA
| | - James Burford
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90033, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine of University of Southern California, Los Angeles, CA, 90033, USA.
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Rahimi M, Kashani AH, Blair NP, Shahidi M. Alterations in Retinal Vascular and Oxygen Metrics in Treated and Untreated Proliferative Diabetic Retinopathy: A Case Report. Case Rep Ophthalmol 2022; 13:686-691. [PMID: 36845454 PMCID: PMC9944214 DOI: 10.1159/000526569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Accepted: 08/03/2022] [Indexed: 11/19/2022] Open
Abstract
Proliferative diabetic retinopathy (PDR) is a vision-threatening complication of diabetes. Panretinal photocoagulation (PRP) and anti-vascular endothelial growth factor (anti-VEGF) are approved treatment modalities aimed at regressing neovascularization. Data are lacking about abnormalities in retinal vascular and oxygen metrics before and after combination treatments. A 32-year-old Caucasian male diagnosed with PDR in the right eye was treated by a combination of PRP and multiple anti-VEGF treatments over a 12-month period. The subject underwent optical coherence tomography (OCT) angiography, Doppler OCT, and retinal oximetry before treatment and at 12 months, which was 6 months following the last treatment. Measurements of vascular metrics (vessel density [VD] and mean arterial and venous diameters [DA, DV]) and oxygen metrics (total retinal blood flow [TRBF], inner retinal oxygen delivery [DO2], metabolism [MO2], and extraction fraction [OEF]) were obtained. Both before and after treatments, VD, TRBF, MO2, and DO2 were below the normal lower confidence limits. Additionally, DV and OEF were decreased after treatments. Alterations in retinal vascular and oxygen metrics were reported for the first time in untreated and treated PDR. Future studies are warranted to evaluate the clinical value of these metrics in PDR.
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Affiliation(s)
- Mansour Rahimi
- aDepartment of Ophthalmology, University of Southern California, Los Angeles, California, USA
| | - Amir H. Kashani
- aDepartment of Ophthalmology, University of Southern California, Los Angeles, California, USA
| | - Norman P. Blair
- bDepartment of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Mahnaz Shahidi
- aDepartment of Ophthalmology, University of Southern California, Los Angeles, California, USA
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Matei N, Leahy S, Blair NP, Burford J, Rahimi M, Shahidi M. Retinal Vascular Physiology Biomarkers in a 5XFAD Mouse Model of Alzheimer's Disease. Cells 2022; 11:2413. [PMID: 35954257 PMCID: PMC9368483 DOI: 10.3390/cells11152413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 07/30/2022] [Accepted: 07/30/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is a neurodegenerative disorder that affects the brain and retina and lacks reliable biomarkers for early diagnosis. As amyloid beta (Aβ) manifestations emerge prior to clinical symptoms and plaques of amyloid may cause vascular damage, identification of retinal vascular biomarkers may improve knowledge of AD pathophysiology and potentially serve as therapeutic targets. The purpose of the current study was to test the hypothesis that retinal hemodynamic and oxygen metrics are altered in 5XFAD mice. METHODS Thirty-two male mice were evaluated at 3 months of age: sixteen 5XFAD transgenic and sixteen wild-type mice. Spectral-domain optical coherence tomography, vascular oxygen tension, and blood flow imaging were performed in one eye of each mouse. After imaging, the imaged and fellow retinal tissues were submitted for histological sectioning and amyloid protein analysis, respectively. Protein analysis was also performed on the brain tissues. RESULTS Retinal physiological changes in venous diameter and blood velocity, arterial and venous oxygen contents, coupled with anatomical alterations in the thickness of retinal cell layers were detected in 5XFAD mice. Moreover, an increase in Aβ42 levels in both the retina and brain tissues was observed in 5XFAD mice. Significant changes in retinal oxygen delivery, metabolism, or extraction fraction were not detected. Based on compiled data from both groups, arterial oxygen content was inversely related to venous blood velocity and nerve fiber/ganglion cell layer thickness. CONCLUSIONS Concurrent alterations in retinal hemodynamic and oxygen metrics, thickness, and tissue Aβ42 protein levels in 5XFAD mice at 3 months of age corresponded to previously reported findings in human AD. Overall, these results suggest that this mouse model can be utilized for studying pathophysiology of AD and evaluating potential therapies.
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Affiliation(s)
- Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
| | - Norman P. Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
| | - James Burford
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
| | - Mansour Rahimi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90033, USA
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Leahy S, Matei N, Blair NP, Shahidi M. Retinal Oxygen Delivery and Metabolism Response to Hyperoxia During Bilateral Common Carotid Artery Occlusion in Rats. Invest Ophthalmol Vis Sci 2022; 63:30. [PMID: 35767246 PMCID: PMC9251813 DOI: 10.1167/iovs.63.6.30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The purpose of the current study was to test the hypothesis that responses of total retinal blood flow (TRBF), inner retinal oxygen delivery (DO2), metabolism (MO2), and extraction fraction (OEF) to hyperoxia are higher after minutes of bilateral common carotid artery occlusion (BCCAO) as compared to days of BCCAO. Methods Twenty-eight rats were subjected to BCCAO for 30 minutes (n = 12), 1 day (n = 8), or 3 days (n = 8). Eight of the 12 rats were also evaluated at baseline, prior to BCCAO. During room air breathing (RA) and 100% O2 inspiration (hyperoxia), blood flow and phosphorescence lifetime imaging were performed to measure TRBF and vascular O2 contents, respectively. DO2, MO2, and OEF were calculated from these measurements. Results After 30 minutes or 3 days of BCCAO, TRBF did not differ between RA and hyperoxia conditions (P ≥ 0.14) but decreased under hyperoxia after 1 day (P = 0.01). Compared to RA, DO2 and MO2 were increased under hyperoxia after 30 minutes of BCCAO (P ≤ 0.02). Additionally, MO2 was decreased under hyperoxia after 1 day of BCCAO (P = 0.04). OEF was decreased under hyperoxia compared to RA (P < 0.001). Under hyperoxia, TRBF and DO2 were reduced after all BCCAO durations compared to baseline (P ≤ 0.04), whereas MO2 did not differ from baseline after 30 minutes of BCCAO (P = 1.00). Conclusions The findings indicate that hyperoxia introduced minutes after ischemia can reduce DO2 impairments and potentially return MO2 to approximately normal values. This information contributes to the knowledge of the effect of supplemental oxygen intervention on TRBF, DO2, MO2, and OEF outcomes after variable durations of ischemia.
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Affiliation(s)
- Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
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Matei N, Leahy S, Blair NP, Shahidi M. Assessment of retinal oxygen metabolism, visual function, thickness and degeneration markers after variable ischemia/reperfusion in rats. Exp Eye Res 2021; 213:108838. [PMID: 34774489 DOI: 10.1016/j.exer.2021.108838] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/25/2021] [Accepted: 11/08/2021] [Indexed: 12/01/2022]
Abstract
After total retinal ischemia induced experimentally by ophthalmic vessel occlusion followed by reperfusion, studies have reported alterations in retinal oxygen metabolism (MO2), delivery (DO2), and extraction fraction (OEF), as well as visual dysfunction and cell loss. In the current study, under variable durations of ischemia/reperfusion, changes in these oxygen metrics, visual function, retinal thickness, and degeneration markers (gliosis and apoptosis) were assessed and related. Additionally, the prognostic value of MO2 for predicting visual function and retinal thickness outcomes was reported. Sixty-one rats were divided into 5 groups of ischemia duration (0 [sham], 60, 90, 120, or 180 min) and 2 reperfusion durations (1 h, 7 days). Phosphorescence lifetime and blood flow imaging, electroretinography, and optical coherence tomography were performed. MO2 reduction was related to visual dysfunction, retinal thinning, increased gliosis and apoptosis after 7-days reperfusion. Impairment in MO2 after 1-h reperfusion predicted visual function and retinal thickness outcomes after 7-days reperfusion. Since MO2 can be measured in humans, findings from analogous studies may find value in the clinical setting.
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Affiliation(s)
- Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, United States
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, United States
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, United States.
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Rahimi M, Leahy S, Blair NP, Shahidi M. Variability of Retinal Oxygen Metrics in Healthy and Diabetic Subjects. Transl Vis Sci Technol 2021; 10:20. [PMID: 34661625 PMCID: PMC8525846 DOI: 10.1167/tvst.10.12.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Previous studies have reported alterations in total retinal blood flow (TRBF), oxygen delivery (DO2), oxygen metabolism (MO2), and oxygen extraction fraction (OEF) due to retinal diseases. The purposes of the current study were to determine variabilities and establish normal confidence intervals (CIs) for these metrics. Methods A total of 22 healthy and 14 diabetic subjects participated in the study. Retinal vascular oxygen saturation (SO2) and TRBF were measured by oximetry and Doppler optical coherence tomography, respectively. DO2, MO2, and OEF were calculated from SO2 and TRBF measurements. Means, standard deviations (SDs), and CIs of metrics were determined in healthy subjects. Intra-visit variability was determined by the mean SDs of repeated measurements. Inter-visit variability was determined by the difference of measurements between two visits. Results TRBF was 44 ± 15 µL/min (95% CI, 37-51) in healthy subjects. Intra-visit variabilities of TRBF were 5 µL/min and 6 µL/min in healthy and diabetic subjects, respectively. Inter-visit variability of TRBF was 3 µL/min in diabetic subjects. DO2, MO2, and OEF were 8.3 ± 2.9 µLO2/min (95% CI, 7.0-9.6), 3.2 ± 0.9 µLO2/min (95% CI, 2.8-3.6), and 0.40 ± 0.08 (95% CI, 0.36-0.43), respectively, in healthy subjects. Inter-visit variabilities of DO2, MO2, and OEF were 0.6 µLO2/min, 0.1 µLO2/min, and 0.03, respectively, in diabetic subjects. Conclusions The findings established variabilities and normal baselines for TRBF, DO2, MO2, and OEF measurements in a small cohort of subjects. Translational Relevance The variability and normal baselines of retinal oxygen metrics may be useful for diagnosing and monitoring patients with retinal diseases.
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Affiliation(s)
- Mansour Rahimi
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, USC Roski Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
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Auvazian SL, Cano J, Leahy S, Karamian P, Kashani A, Moshfeghi A, Ameri H, Blair NP, Shahidi M. Relating Retinal Vascular Oxygen Saturation and Microvasculature Morphology at Progressive Stages of Diabetic Retinopathy. Transl Vis Sci Technol 2021; 10:4. [PMID: 34111249 PMCID: PMC8107511 DOI: 10.1167/tvst.10.6.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose Diabetic retinopathy (DR) is a common cause of vision loss in working age adults and presents changes in retinal vessel oxygenation and morphology. The purpose of this study was to test the hypothesis that there is an association of retinal vessel oxygen saturation with vessel density (VD) and tortuosity in DR. Methods Ninety-five subjects were classified in the following groups: nondiabetic control (N = 25), no DR (N = 28), mild nonproliferative DR (NPDR; N = 21), moderate to severe NPDR (N = 14), or treated proliferative DR (PDR; N = 7). Retinal oximetry was performed to measure arterial and venous oxygen saturation (SO2A and SO2V) and calculate oxygen extraction fraction (OEF). Optical coherence tomography angiography (OCTA) was performed for measurements of VD and vessel tortuosity index (VTI). Results There were statistically significant differences in SO2A and SO2V among groups (P< 0.004). SO2A and SO2V were higher in the PDR group compared to the control group and SO2V was also higher in the moderate to severe NPDR group. VD differed significantly among groups (P = 0.003), whereas VTI was not significantly different (P = 0.22). Compared to the control group, VD was lower in moderate to severe NPDR and PDR groups. VD was also lower in the PDR group than that in the no DR group (P = 0.03). There was a significant correlation of VTI with SO2V (r = 0.32, P = 0.002) and OEF (r = −0.35, P = 0.001). Conclusions Retinal vessel morphology, oxygenation, and tissue oxygen extraction were associated with each other in a cohort of subjects with and without DR. Translational Relevance The findings of this study have the potential to improve clinical management of DR by providing better understanding of human disease pathophysiology and propelling future studies to identify multiple image-based biomarkers for improved disease diagnosis and monitoring.
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Affiliation(s)
- Selin L Auvazian
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Jennifer Cano
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Preny Karamian
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Amir Kashani
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Andrew Moshfeghi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Hossein Ameri
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
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Rahimi M, Leahy S, Matei N, Blair NP, Jeong S, Craft CM, Shahidi M. Assessment of inner retinal oxygen metrics and thickness in a mouse model of inherited retinal degeneration. Exp Eye Res 2021; 205:108480. [PMID: 33539865 DOI: 10.1016/j.exer.2021.108480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 01/15/2021] [Accepted: 01/26/2021] [Indexed: 12/20/2022]
Abstract
The retinal degeneration 1 (rd1) mouse is a well-established model of inherited retinal degeneration, displaying photoreceptor degeneration and retinal vasculature damage. The purpose of the current study was to determine alterations in the rate of oxygen delivery from retinal circulation (DO2), the rate of oxygen extraction from the retinal circulation for metabolism (MO2), and oxygen extraction fraction (OEF) in rd1 mice. The study was performed in a total of 18 wild type (WT) and 10 rd1 mice at both 3-weeks and 12-weeks of age. Retinal arterial and venous oxygen contents (O2A and O2V) were measured using phosphorescence lifetime imaging. Total retinal blood flow (TRBF) was determined by fluorescence and red-free imaging. DO2 and MO2 were determined as TRBF × O2A and TRBF × (O2A-O2V), respectively. OEF was calculated as MO2/DO2. The thickness of individual retinal layers was measured from histology sections and inner retina (IR) and total retina (TR) thickness were calculated. TRBF, DO2 and MO2 were lower in rd1 mice compared to WT mice (P ≤ 0.001), whereas OEF was not significantly different between rd1 and WT mice (P = 0.4). TRBF and DO2 were lower at 3-weeks of age compared to 12-weeks of age (P ≤ 0.01), while MO2 was not significantly different between age groups (P = 0.4) and OEF was higher at 3-weeks of age compared to 12-weeks of age (P = 0.003). Additionally, the outer and inner retinal cell layer thicknesses were decreased in rd1 mice at 12-weeks of age compared to both age-matched WT mice and rd1 mice at 3-weeks of age (P ≤ 0.02). MO2 was directly correlated with both IR and TR thickness (R ≥ 0.50; P ≤ 0.03, N = 20). The findings indicate that the rate oxygen is supplied by the retinal circulation is decreased and the reduction in oxygen extracted for metabolism is related to retinal cell layer thinning in rd1 mice.
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Affiliation(s)
- Mansour Rahimi
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Nathanael Matei
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Shinwu Jeong
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA
| | - Cheryl Mae Craft
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA; Department of Integrative Anatomical Sciences, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, USC Roski Eye Institute, Los Angeles, CA, USA.
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12
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McAnany JJ, Park JC, Chau FY, Leiderman YI, Lim JI, Blair NP. AMPLITUDE LOSS OF THE HIGH-FREQUENCY FLICKER ELECTRORETINOGRAM IN EARLY DIABETIC RETINOPATHY. Retina 2020; 39:2032-2039. [PMID: 30024576 DOI: 10.1097/iae.0000000000002262] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate retinal dysfunction in diabetic patients who have mild or no nonproliferative diabetic retinopathy (DR) using the high-frequency flicker electroretinogram. METHODS Light-adapted flicker electroretinograms were recorded from 15 diabetic patients who have no clinically apparent retinopathy, 15 diabetic patients who have mild nonproliferative DR, and 15 nondiabetic, age-equivalent controls. Electroretinograms were elicited by full-field flicker at 2 temporal frequencies, 31.25 and 62.5 Hz, and were recorded using conventional techniques. Amplitude and timing of the flicker responses were compared among the groups and correlated with clinical characteristics including age, acuity, disease duration, and HbA1c. RESULTS The 31.25-Hz flicker amplitude was slightly, but nonsignificantly, smaller for subjects with no DR and mild nonproliferative DR , compared with the control group (both t < 1.38, P > 0.31); small, nonsignificant response delays for both patient groups were also observed (both t < 1.57, P > 0.12). By contrast, there were significant amplitude reductions for the 62.5-Hz flicker stimulus: mean amplitude was reduced by 32% for subjects with no DR and by 41% for subjects with mild nonproliferative DR (both t > 2.92 and P < 0.01). Response timing at 62.5 Hz did not differ significantly from control for either group (both t < 1.2 and P > 0.39). Electroretinogram amplitude and timing were not correlated significantly with clinical characteristics. CONCLUSION The 62.5-Hz flicker electroretinogram is useful for evaluating retinal dysfunction in diabetic patients who have mild or no DR because this response can be significantly reduced. Attenuation of the high-frequency flicker electroretinogram, which is primarily generated by bipolar cells, suggests a relatively early retinal site of neural dysfunction.
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Affiliation(s)
- J Jason McAnany
- Departments of Ophthalmology and Visual Sciences, and.,Bioengineering, University of Illinois at Chicago, Chicago, Illinois
| | - Jason C Park
- Departments of Ophthalmology and Visual Sciences, and
| | - Felix Y Chau
- Departments of Ophthalmology and Visual Sciences, and
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13
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Cano J, O’neill WD, Penn RD, Blair NP, Kashani AH, Ameri H, Kaloostian CL, Shahidi M. Classification of advanced and early stages of diabetic retinopathy from non-diabetic subjects by an ordinary least squares modeling method applied to OCTA images. Biomed Opt Express 2020; 11:4666-4678. [PMID: 32923070 PMCID: PMC7449717 DOI: 10.1364/boe.394472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 07/04/2020] [Accepted: 07/12/2020] [Indexed: 05/02/2023]
Abstract
As the prevalence of diabetic retinopathy (DR) continues to rise, there is a need to develop computer-aided screening methods. The current study reports and validates an ordinary least squares (OLS) method to model optical coherence tomography angiography (OCTA) images and derive OLS parameters for classifying proliferative DR (PDR) and no/mild non-proliferative DR (NPDR) from non-diabetic subjects. OLS parameters were correlated with vessel metrics quantified from OCTA images and were used to determine predicted probabilities of PDR, no/mild NPDR, and non-diabetics. The classification rates of PDR and no/mild NPDR from non-diabetic subjects were 94% and 91%, respectively. The method had excellent predictive ability and was validated. With further development, the method may have potential clinical utility and contribute to image-based computer-aided screening and classification of stages of DR and other ocular and systemic diseases.
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Affiliation(s)
- Jennifer Cano
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90007, USA
| | - William D. O’neill
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Richard D. Penn
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
- Department of Neurosurgery, Rush University and Hospital, Chicago, IL 60612, USA
| | - Norman P. Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Amir H. Kashani
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90007, USA
| | - Hossein Ameri
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90007, USA
| | - Carolyn L. Kaloostian
- Department of Family Medicine, University of Southern California, Los Angeles, CA 90007, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA 90007, USA
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14
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Blair NP, Leahy S, Nathanael Matei, Shahidi M. Control of retinal blood flow levels by selected combinations of cervical arterial ligations in rat. Exp Eye Res 2020; 197:108088. [PMID: 32502531 DOI: 10.1016/j.exer.2020.108088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 05/26/2020] [Accepted: 05/27/2020] [Indexed: 10/24/2022]
Abstract
The effect of various combinations of cervical arterial ligations (Combinations) on retinal blood flow (RBF) levels is not known in rats. We hypothesized: 1) No artery exists between the Circle of Willis and the eye, 2) Selective Combinations enable varying RBF levels between normal and zero, 3) In certain Combinations, the capillary bed of the head participates in supplying the eye. Twenty-six Combinations were studied in one eye of 20 Long-Evans rats under general anesthesia. RBF was quantitatively evaluated with our published imaging methods based on direct measurements of venous diameter and blood velocity from the displacement of fluorescent microspheres over time. For each Combination, one or more RBF values (runs) were measured. Data were obtained from 59 runs (2.9 ± 2.7 runs/rat). Levels of RBF ranged from normal to zero. An artery between the Circle of Willis and the eye was excluded. With some Combinations, flow traversed the capillary bed. Combinations were consolidated into five Groups based on the blood flow paths remaining after the ligations. A mixed linear model accounting for multiple measurements in the same eye demonstrated an effect of Group on RBF (P < 0.0005). By major source of ocular blood supply, the trend of RBF levels was: ipsilateral carotid artery > contralateral carotid artery > ipsilateral distal internal carotid artery retrograde from Circle of Willis. The findings advanced knowledge of the sources of blood supply to the rat eye and demonstrated a method of selective cervical arterial ligations for varying RBF levels with potential to impact future retinal ischemia research.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, United States.
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, United States.
| | - Nathanael Matei
- Department of Ophthalmology, University of Southern California, United States.
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, United States.
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15
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Matei N, Leahy S, Auvazian S, Thomas B, Blair NP, Shahidi M. Relation of Retinal Oxygen Measures to Electrophysiology and Survival Indicators after Permanent, Incomplete Ischemia in Rats. Transl Stroke Res 2020; 11:1273-1286. [PMID: 32207038 DOI: 10.1007/s12975-020-00799-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 02/21/2020] [Accepted: 02/27/2020] [Indexed: 12/28/2022]
Abstract
Studies in experimental ischemia models by permanent bilateral common carotid artery occlusion (BCCAO) have reported reduced retinal electrophysiological function, coupled with inner retinal degeneration and gliosis. In the current study, we tested the hypothesis that long-term (up to 14 days) BCCAO impairs oxygen delivery (DO2), which affects oxygen metabolism (MO2) and extraction fraction (OEF), electrophysiological function, morphology, and biochemical pathways. Twenty-one rats underwent BCCAO (N = 12) or sham surgery (N = 9) and were evaluated in separate groups after 3, 7, or 14 days. Electroretinography (ERG), optical coherence tomography, blood flow and vascular oxygen tension imaging, and morphological and biochemical evaluations were performed in both eyes. Reduced ERG b-wave amplitudes and delayed implicit times were reported at 3, 7, and 14 days following BCCAO. Total retinal blood flow, MO2, and DO2 were reduced in all BCCAO groups. OEF was increased in both 3- and 7-day groups, while no significant difference was observed in OEF at 14 days compared to the sham group. At 14 days following BCCAO, total and inner retinal layer thickness was reduced, while the outer nuclear layer thickness and gliosis were increased. There was an increase in nuclei containing fragmented DNA at 3 days following BCCAO. The compensatory elevation in OEF following BCCAO did not meet the tissue demand, resulting in the subsequent reduction of MO2. The associations between retinal MO2, DO2, and retinal function were shown to be significant in the sequelae of persistent ischemia. In sum, measurements of DO2, MO2, and OEF may become useful for characterizing salvageable tissue in vision-threatening pathologies.
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Affiliation(s)
- Nathanael Matei
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Sophie Leahy
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Selin Auvazian
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Biju Thomas
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA.
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16
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Matei N, Leah S, Auvazian S, Blair NP, Shahidi M. Abstract WP165: Retinal Oxygen Metabolic, Anatomical, and Biochemical Changes in Experimental Carotid Artery Occlusion. Stroke 2020. [DOI: 10.1161/str.51.suppl_1.wp165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Purpose:
Retinal ischemia has been implicated in vision-threatening diseases. Permanent bilateral common carotid artery occlusion (BCCAO) studies have reported retinal degeneration and gliosis, as well as cerebral degeneration. We hypothesized that BCCAO-induced long-term (3 to 14 days) impairments to oxygen delivery (DO
2
), extraction fraction (OEF), and metabolism (MO
2
) affect cellular morphology and biochemical pathways.
Methods:
Twenty-one rats underwent BCCAO or sham surgery. Blood flow and vascular oxygen tension imaging was performed in both eyes. Images were analyzed to derive retinal arterial and venous oxygen contents (O
2A
, O
2V
), arteriovenous oxygen content difference (O
2AV
), and total retinal blood flow (TRBF). The following equations were used: DO
2
=TRBF*O
2A
; MO
2
=TRBF*O
2AV
; OEF=MO
2
/DO
2
. After imaging, immunohistochemistry and histological assays were performed on retinal sections.
Results:
Compared to the sham group, DO
2
was reduced in 3-day (β=-622 nLO
2
/min), 7-day (β=-614 nLO
2
/min), and 14-day (β=-605 nLO
2
/min) BCCAO groups. MO
2
was reduced in 3-day (β=-215 nLO
2
/min), 7-day (β=-256 nLO
2
/min), and 14-day (β=-262 nLO
2
/min) BCCAO groups. Compared to the sham group, OEF was increased in 3-day (β=0.405) and 7-day (β=0.209) BCCAO groups. Compared to the sham group, the thickness of the nerve fiber (β=-14.6 μm), inner nuclear (β=-7.21 μm), outer plexiform (β=-6.70 μm), and inner retina (β=-30.7 μm) layers were decreased, while thickness of the outer nuclear layer was increased (β=7.88 μm) in the 14-day BCCAO group. Gliosis was increased in the 14-day BCCAO group compared to all other groups. Compared to the sham group, TUNEL-positive cells in inner and outer nuclear layers were increased in the 3-day BCCAO group.
Conclusions:
The findings confirm our hypothesis that BCCAO-induced reduction in retinal DO
2
resulted in increased OEF, impairment of MO
2
, and inner retinal cell death after 3 days, whereas increased gliosis and degeneration of inner retinal cells were observed after 14 days. When compared to brain literature, the retina—an extension of the diencephalon-- showed a similar reduction in blood flow and increase in both OEF and cell-death at 3-days following BCCAO.
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Affiliation(s)
| | - Sophie Leah
- Univ of Southern California, Los Angeles, CA
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17
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Karamian P, Burford J, Farzad S, Blair NP, Shahidi M. Alterations in Retinal Oxygen Delivery, Metabolism, and Extraction Fraction During Bilateral Common Carotid Artery Occlusion in Rats. Invest Ophthalmol Vis Sci 2019; 60:3247-3253. [PMID: 31343655 PMCID: PMC6660186 DOI: 10.1167/iovs.19-27227] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Purpose The purpose of the current study was to investigate alterations in retinal oxygen delivery, metabolism, and extraction fraction and elucidate their relationships in an experimental model of retinal ischemia. Methods We subjected 14 rats to permanent bilateral common carotid artery occlusion using clamp or suture ligation, or they underwent sham procedure. Within 30 minutes of the procedure, phosphorescence lifetime imaging was performed to measure retinal vascular oxygen tension and derive arterial and venous oxygen contents, and arteriovenous oxygen content difference. Fluorescent microsphere and red-free retinal imaging were performed to measure total retinal blood flow. Retinal oxygen delivery rate (DO2), oxygen metabolism rate (MO2), and oxygen extraction fraction (OEF) were calculated. Results DO2 and MO2 were lower in ligation and clamp groups compared to the sham group, and also lower in the ligation group compared to the clamp group (P ≤ 0.05). OEF was higher in the ligation group compared to clamp and sham groups (P ≤ 0.03). The relationships of MO2 and OEF with DO2 were mathematically modeled by exponential functions. With moderate DO2 reductions, OEF increased while MO2 minimally decreased. Under severe DO2 reductions, OEF reached a maximum value and subsequently MO2 decreased with DO2. Conclusions The findings improve knowledge of mechanisms that can maintain MO2 and may clarify the pathophysiology of retinal ischemic injury.
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Affiliation(s)
- Preny Karamian
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - James Burford
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Shayan Farzad
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
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18
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Blair NP, Tan MR, Felder AE, Shahidi M. Retinal Oxygen Delivery, Metabolism and Extraction Fraction and Retinal Thickness Immediately Following an Interval of Ophthalmic Vessel Occlusion in Rats. Sci Rep 2019; 9:8092. [PMID: 31147557 PMCID: PMC6542852 DOI: 10.1038/s41598-019-44250-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 05/09/2019] [Indexed: 11/30/2022] Open
Abstract
Limited knowledge is currently available about alterations of retinal blood flow (F), oxygen delivery (DO2), oxygen metabolism (MO2), oxygen extraction fraction (OEF), or thickness after the ophthalmic blood vessels have been closed for a substantial interval and then reopened. We ligated the ophthalmic vessels for 120 minutes in one eye of 17 rats, and measured these variables within 20 minutes after release of the ligature in the 10 rats which had immediate reflow. F, DO2 and MO2 were 5.2 ± 3.1 μL/min, 428 ± 271 nL O2/min, and 234 ± 133 nL O2/min, respectively, that is, to 58%, 46% and 60% of values obtained from normal fellow eyes (P < 0.004). OEF was 0.65 ± 0.23, 148% of normal (P = 0.03). Inner and total retinal thicknesses were 195 ± 24 and 293 ± 20 μm, respectively, 117% and 114% of normal, and inversely related to MO2 (P ≤ 0.02). These results reflect how much energy is available to the retina immediately after an interval of nonperfusion for 120 minutes. Thus, they elucidate aspects of the pathophysiology of nonperfusion retinal injury and may improve therapy in patients with retinal artery or ophthalmic artery obstructions.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, USA
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, USA
| | - Anthony E Felder
- Richard and Loan Hill Department of Bioengineering, University of Illinois at Chicago, Chicago, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, USA.
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19
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Shahidi M, Felder AE, Tan O, Blair NP, Huang D. Retinal Oxygen Delivery and Metabolism in Healthy and Sickle Cell Retinopathy Subjects. Invest Ophthalmol Vis Sci 2019; 59:1905-1909. [PMID: 29677351 PMCID: PMC5886143 DOI: 10.1167/iovs.17-23647] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Purpose Reduction in inner retinal oxygen delivery (DO2) can cause retinal hypoxia and impair inner retinal oxygen metabolism (MO2), leading to vision loss. The purpose of the current study was to establish measurements of DO2 and MO2 in healthy subjects and test the hypothesis that DO2 and MO2 are reduced in sickle cell retinopathy (SCR) subjects. Methods Dual wavelength retinal oximetry and Doppler optical coherence tomography were performed in 12 healthy control and 12 SCR subjects. Images were analyzed to measure retinal arterial and venous oxygen content (O2A and O2V), venous diameter (DV), and total retinal blood flow (TRBF). Retinal arteriovenous oxygen content difference (O2AV), DO2, MO2, and oxygen extraction fraction (OEF) were calculated according to the following equations: O2AV = O2A - O2V; DO2 = TRBF * O2A; MO2 = TRBF * O2AV; OEF = MO2/DO2. Results Retinal DV and TRBF were higher in the SCR group as compared to the control group, whereas, O2A, O2V, and O2AV were lower in SCR group as compared to the control group. DO2, MO2, and OEF were not significantly different between control and SCR groups. MO2 and DO2 were linearly related, such that higher MO2 was associated with higher DO2. There was an inverse relationship between TRBF and OEF, such that lower TRBF was associated with higher OEF. Conclusions Increased blood flow compensated for decreased oxygen content, thereby maintaining DO2, MO2, and OEF at predominately lower stages of SCR. Quantitative assessment of these parameters has the potential to advance knowledge and improve diagnostic evaluation of retinal ischemic conditions.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
| | - Anthony E Felder
- Richard and Loan Hill Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Ou Tan
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, United States
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - David Huang
- Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, United States
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20
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Blair NP, Tan MR, Felder AE, Teng PY, Wanek J, Shahidi M. Retinal tissue oxygen tension and consumption during light flicker stimulation in rat. Exp Eye Res 2018; 175:207-211. [PMID: 30121195 DOI: 10.1016/j.exer.2018.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 08/09/2018] [Accepted: 08/12/2018] [Indexed: 10/28/2022]
Abstract
Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO2) but not the outer retinal oxygen consumption rate (QO2). In 17 rats, tPO2 depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO2 profile metrics, including mean inner retinal tPO2, maximum outer retinal tPO2 and minimum outer retinal tPO2 were determined. QO2 was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO2 profile metrics or QO2 differences depended on the duration of light flicker stimulation (R2 ≤ 0.03). No significant change in any of the tPO2 profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO2 from 0.53 ± 0.29 to 0.38 ± 0.30 mL O2/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO2.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Anthony E Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL, 60612, USA.
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21
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Abstract
Purpose Retinal ischemic injury depends on grade and duration of an ischemic insult. We developed a method to induce ischemic injury in rats permitting: (1) Variable grades of retinal blood flow (F) reduction, (2) controllable duration of F reduction, (3) injury without collateral neural damage, and (4) optical measurements of F and O2-related factors: O2 delivery (DO2), O2 extraction fraction (OEF), and metabolic rate of O2 (MO2). Methods In five anesthetized rats the left common carotid artery (CA) was ligated and the right CA was exposed. A variable clamp having a backstop and a rod mounted on a micromanipulator straddled the right CA. Advancing the rod with the micromanipulator produced graded compressions of the CA. F and O2-related factors were measured with established optical techniques. Results Four to seven grades of F for at least 10 minutes were achieved per rat. F decreased only with compressions of over 60%. DO2 changed in proportion to F, particularly at low F. As F decreased, OEF initially changed little, but then rose steeply to its maximum of 1 when F was approximately 4 μL/min. MO2 was stable with reduced F until OEF maximized, after which it decreased progressively. Conclusions This model in rats permits acute, graded inner retinal ischemia that is reversible after prescribed durations, does not otherwise injure the eye and allows optical measurement of important physiologic factors during ischemia. Translational Relevance This model will allow improved understanding of retinal ischemic injury and enable better management of this common, sight-threatening affliction.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Anthony E Felder
- Richard and Loan Hill Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Michael R Tan
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
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22
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Abstract
Purpose To mathematically model the temporal dynamic responses of retinal vessel diameter (D), oxygen saturation (SO2), and inner retinal oxygen extraction fraction (OEF) to light flicker and to describe their responses to its cessation in humans. Methods In 16 healthy subjects (age: 60 ± 12 years), retinal oximetry was performed before, during, and after light flicker stimulation. At each time point, five metrics were measured: retinal arterial and venous D (DA, DV) and SO2 (SO2A, SO2V), and OEF. Intra- and intersubject variability of metrics was assessed by coefficient of variation of measurements before flicker within and among subjects, respectively. Metrics during flicker were modeled by exponential functions to determine the flicker-induced steady state metric values and the time constants of changes. Metrics after the cessation of flicker were compared to those before flicker. Results Intra- and intersubject variability for all metrics were less than 6% and 16%, respectively. At the flicker-induced steady state, DA and DV increased by 5%, SO2V increased by 7%, and OEF decreased by 13%. The time constants of DA and DV (14, 15 seconds) were twofold smaller than those of SO2V and OEF (39, 34 seconds). Within 26 seconds after the cessation of flicker, all metrics were not significantly different from before flicker values (P ≥ 0.07). Conclusions Mathematical modeling revealed considerable differences in the time courses of changes among metrics during flicker, indicating flicker duration should be considered separately for each metric. Future application of this method may be useful to elucidate alterations in temporal dynamic responses to light flicker due to retinal diseases.
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Affiliation(s)
- Anthony E Felder
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States.,Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
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Blair NP, Wanek J, Felder AE, Joslin CE, Kresovich JK, Lim JI, Chau FY, Leiderman Y, Shahidi M. Retinal Oximetry and Vessel Diameter Measurements With a Commercially Available Scanning Laser Ophthalmoscope in Diabetic Retinopathy. Invest Ophthalmol Vis Sci 2017; 58:5556-5563. [PMID: 29079858 PMCID: PMC5656420 DOI: 10.1167/iovs.17-21934] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 09/07/2017] [Indexed: 02/03/2023] Open
Abstract
Purpose To test the hypothesis that retinal vascular diameter and hemoglobin oxygen saturation alterations, according to stages of diabetic retinopathy (DR), are discernible with a commercially available scanning laser ophthalmoscope (SLO). Methods One hundred eighty-one subjects with no diabetes (No DM), diabetes with no DR (No DR), nonproliferative DR (NPDR), or proliferative DR (PDR, all had photocoagulation) underwent imaging with an SLO with dual lasers (532 nm and 633 nm). Customized image analysis software determined the diameters of retinal arteries and veins (DA and DV) and central retinal artery and vein equivalents (CRAE and CRVE). Oxygen saturations of hemoglobin in arteries and veins (SO2A and SO2V) were estimated from optical densities of vessels on images at the two wavelengths. Statistical models were generated by adjusting for effects of sex, race, age, eye, and fundus pigmentation. Results DA, CRAE, and CRVE were reduced in PDR compared to No DM (P ≤ 0.03). DV and CRVE were similar between No DM and No DR, but they were higher in NPDR than No DR (P ≤ 0.01). Effect of stage of disease on SO2A differed by race, being increased relative to No DM in NPDR and PDR in Hispanic participants only (P ≤ 0.02). Relative to No DM, SO2V was increased in NPDR and PDR (P ≤ 0.05). Conclusions Alterations in retinal vascular diameters and SO2 by diabetic retinopathy stage can be detected with a widely available SLO, and covariates such as race can influence the results.
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Affiliation(s)
- Norman P. Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Anthony E. Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Charlotte E. Joslin
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
- Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois, United States
- University of Illinois Cancer Center, Population Health, Behavior, and Outcomes Program, Chicago, Illinois, United States
| | - Jacob K. Kresovich
- Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Jennifer I. Lim
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Felix Y. Chau
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Yannek Leiderman
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, Los Angeles, California, United States
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Abstract
PURPOSE Inadequate retinal oxygenation occurs in many vision-threatening retinal diseases, including diabetic retinopathy, retinal vascular occlusions, and age-related macular degeneration. Therefore, techniques that assess retinal oxygenation are necessary to understand retinal physiology in health and disease. The purpose of the current study is to report a method for the three-dimensional (3D) imaging of retinal tissue oxygen tension (tPO2) in rats. METHODS Imaging was performed in Long Evans pigmented rats under systemic normoxia (N = 6) or hypoxia (N = 3). A vertical laser line was horizontally scanned on the retina and a series of optical section phase-delayed phosphorescence images were acquired. From these images, phosphorescence volumes at each phase delay were constructed and a 3D retinal tPO2 volume was generated. Retinal tPO2 volumes were quantitatively analyzed by generating retinal depth profiles of mean tPO2 (MtPO2) and the spatial variation of tPO2 (SVtPO2). The effects of systemic condition (normoxia/hypoxia) and retinal depth on MtPO2 and SVtPO2 were determined by mixed linear model. RESULTS Each 3D retinal tPO2 volume was approximately 500 × 750 × 200 μm (horizontal × vertical × depth) and consisted of 45 en face tPO2 images through the retinal depth. MtPO2 at the chorioretinal interface was significantly correlated with systemic arterial oxygen tension (P = 0.007; N = 9). There were significant effects of both systemic condition and retinal depth on MtPO2 and SVtPO2, such that both were lower under hypoxia than normoxia and higher in the outer retina than inner retina (P < 0.001). CONCLUSION For the first time, 3D imaging of retinal tPO2 was demonstrated, with potential future application for assessment of physiological alterations in animal models of retinal diseases.
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Affiliation(s)
- Anthony E Felder
- a Department of Bioengineering , University of Illinois at Chicago , Chicago IL, USA.,b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Justin Wanek
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Pang-Yu Teng
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Norman P Blair
- b Department of Ophthalmology and Visual Science , University of Illinois at Chicago , Chicago IL, USA
| | - Mahnaz Shahidi
- c Department of Ophthalmology , University of Southern California , Los Angeles CA, USA
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Wanek J, Blair NP, Chau FY, Lim JI, Leiderman YI, Shahidi M. Alterations in Retinal Layer Thickness and Reflectance at Different Stages of Diabetic Retinopathy by En Face Optical Coherence Tomography. Invest Ophthalmol Vis Sci 2017; 57:OCT341-7. [PMID: 27409491 PMCID: PMC4968784 DOI: 10.1167/iovs.15-18715] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Purpose This article reports a method for en face optical coherence tomography (OCT) imaging and quantitative assessment of alterations in both thickness and reflectance of individual retinal layers at different stages of diabetic retinopathy (DR). Methods High-density OCT raster volume scans were acquired in 29 diabetic subjects divided into no DR (NDR) or non-proliferative DR (NPDR) groups and 22 control subjects (CNTL). A customized image segmentation method identified eight retinal layer interfaces and generated en face thickness maps and reflectance images for nerve fiber layer (NFL), ganglion cell and inner plexiform layers (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE). Mean thickness and intensity values were calculated in nine macular subfields for each retinal layer. Results En face thickness maps and reflectance images of retinal layers in CNTL subjects corresponded to normal retinal anatomy. Total retinal thickness correlated negatively with age in nasal subfields (R ≤−0.31; P ≤ 0.03, N = 51). In NDR subjects, NFL and OPL thickness were decreased (P = 0.05), and ONL thickness was increased (P = 0.04) compared to CNTL. In NPDR subjects, GCLIPL thickness was increased in perifoveal subfields (P< 0.05) and INL intensity was higher in all macular subfields (P = 0.04) compared to CNTL. Conclusions Depth and spatially resolved retinal thickness and reflectance measurements are potential biomarkers for assessment and monitoring of DR.
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Blair NP, Wanek J, Felder AE, Brewer KC, Joslin CE, Shahidi M. Inner Retinal Oxygen Delivery, Metabolism, and Extraction Fraction in Ins2Akita Diabetic Mice. Invest Ophthalmol Vis Sci 2017; 57:5903-5909. [PMID: 27802520 PMCID: PMC5096417 DOI: 10.1167/iovs.16-20082] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Purpose Retinal nonperfusion and hypoxia are important factors in human diabetic retinopathy, and these presumably inhibit energy production and lead to cell death. The purpose of this study was to elucidate the effect of diabetes on inner retinal oxygen delivery and metabolism in a mouse model of diabetes. Methods Phosphorescence lifetime and blood flow imaging were performed in spontaneously diabetic Ins2Akita (n = 22) and nondiabetic (n = 22) mice at 12 and 24 weeks of age to measure retinal arterial (O2A) and venous (O2V) oxygen contents and total retinal blood flow (F). Inner retinal oxygen delivery (DO2) and metabolism (MO2) were calculated as F ∗ O2A and F ∗ (O2A − O2V), respectively. Oxygen extraction fraction (OEF), which equals MO2/DO2, was calculated. Results DO2 at 12 weeks were 112 ± 40 and 97 ± 29 nL O2/min in nondiabetic and diabetic mice, respectively (NS), and 148 ± 31 and 85 ± 37 nL O2/min at 24 weeks, respectively (P < 0.001). MO2 were 65 ± 31 and 66 ± 27 nL O2/min in nondiabetic and diabetic mice at 12 weeks, respectively, and 79 ± 14 and 54 ± 28 nL O2/min at 24 weeks, respectively (main effects = NS). At 12 weeks OEF were 0.57 ± 0.17 and 0.67 ± 0.09 in nondiabetic and diabetic mice, respectively, and 0.54 ± 0.07 and 0.63 ± 0.08 at 24 weeks, respectively (main effect of diabetes: P < 0.01). Conclusions Inner retinal MO2 was maintained in diabetic Akita mice indicating that elevation of the OEF adequately compensated for reduced DO2 and prevented oxidative metabolism from being limited by hypoxia.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Anthony E Felder
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Katherine C Brewer
- Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Charlotte E Joslin
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States 2Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, Chicago, Illinois, United States 3University of Illinois Cancer Center, Population Health, Behavior, and Outcomes Program, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
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Felder AE, Wanek J, Blair NP, Joslin CE, Brewer KC, Chau FY, Lim JI, Leiderman YI, Shahidi M. The Effects of Diabetic Retinopathy Stage and Light Flicker on Inner Retinal Oxygen Extraction Fraction. Invest Ophthalmol Vis Sci 2017; 57:5586-5592. [PMID: 27768785 PMCID: PMC6016433 DOI: 10.1167/iovs.16-20048] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose We determined the effects of light flicker and diabetic retinopathy (DR) stage on retinal vascular diameter (D), oxygen saturation (SO2), and inner retinal oxygen extraction fraction (OEF). Methods Subjects were categorized as nondiabetic control (NC, n = 42), diabetic with no clinical DR (NDR; n = 32), nonproliferative DR (NPDR; n = 42), or proliferative DR (PDR; n = 14). Our customized optical imaging system simultaneously measured arterial and venous D (DA, DV) and SO2 (SO2A, SO2V) before and during light flicker. Inner retinal OEF was derived from SO2 values. Light flicker-induced ratios of metrics (DAR, DVR, SO2AR, SO2VR, OEFR) were calculated. Results Arterial D was larger in NPDR compared to NC (P = 0.01) and PDR (P = 0.002), whereas DV was similar among groups (P ≥ 0.16). Light flicker increased DA and DV (P ≤ 0.004), but DAR and DVR were similar among groups (P ≥ 0.09). Arterial SO2 was higher in all groups compared to NC (P ≤ 0.02) and higher in PDR compared to NDR and NPDR (P<0.001). Arterial SO2 did not change with light flicker (P ≥ 0.1). Venous SO2 was higher in NPDR and PDR compared to NC and NDR (P ≤ 0.02). Light flicker increased SO2V in NC, NDR, and PDR (P ≤ 0.003), and SO2VR was lower in NPDR compared to NC and NDR (P ≤ 0.05). Inner retinal OEF was lower in NPDR compared to NDR and PDR (P ≤ 0.02). Light flicker decreased OEF (P ≤ 0.03), but OEFR was greater in NPDR compared to NC and NDR (P ≤ 0.03). Conclusions The findings of alterations in retinal D, SO2, OEF, and their light flicker-induced responses at stages of DR may be useful to elucidate the pathophysiology of DR.
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Affiliation(s)
- Anthony E Felder
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Norman P Blair
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Charlotte E Joslin
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States 2School of Public Health, Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, Illinois, United States 3University of Illinois Cancer Center, Population Health, Behavior, and Outcomes Program, Chicago, Illinois, United States
| | - Katherine C Brewer
- School of Public Health, Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Felix Y Chau
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Jennifer I Lim
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Yannek I Leiderman
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
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Park JC, Chen YF, Blair NP, Chau FY, Lim JI, Leiderman YI, Shahidi M, McAnany JJ. Pupillary responses in non-proliferative diabetic retinopathy. Sci Rep 2017; 7:44987. [PMID: 28332564 PMCID: PMC5362954 DOI: 10.1038/srep44987] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 02/17/2017] [Indexed: 01/24/2023] Open
Abstract
The goal of this study was to determine the extent of rod-, cone-, and melanopsin-mediated pupillary light reflex (PLR) abnormalities in diabetic patients who have non-proliferative diabetic retinopathy (NPDR). Fifty diabetic subjects who have different stages of NPDR and 25 age-equivalent, non-diabetic controls participated. PLRs were measured in response to full-field, brief-flash stimuli under conditions that target the rod, cone, and intrinsically-photosensitive (melanopsin) retinal ganglion cell pathways. Pupil responses were compared among the subjects groups using age-corrected linear mixed models. Compared to control, the mean baseline pupil diameters were significantly smaller for all patient groups in the dark (all p < 0.001) and for the moderate-severe NPDR group in the light (p = 0.003). Pairwise comparisons indicated: (1) the mean melanopsin-mediated PLR was significantly reduced in the mild and moderate-severe groups (both p < 0.001); (2) the mean cone-mediated PLR was reduced significantly in the moderate-severe group (p = 0.008); (3) no significant differences in the mean rod-mediated responses. The data indicate abnormalities in NPDR patients under conditions that separately assess pupil function driven by different photoreceptor classes. The results provide evidence for compromised neural function in these patients and provide a promising approach for quantifying their neural abnormalities.
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Affiliation(s)
- Jason C Park
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
| | - Yi-Fan Chen
- Center for Clinical and Translational Sciences, University of Illinois at Chicago, 914 S Wood Street, Chicago, IL 60612, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
| | - Felix Y Chau
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
| | - Jennifer I Lim
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
| | - Yannek I Leiderman
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology, University of Southern California, 1450 San Pablo St, Los Angeles, CA 90033, USA
| | - J Jason McAnany
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA
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Khansari MM, O’Neill W, Penn R, Chau F, Blair NP, Shahidi M. Automated fine structure image analysis method for discrimination of diabetic retinopathy stage using conjunctival microvasculature images. Biomed Opt Express 2016; 7:2597-606. [PMID: 27446692 PMCID: PMC4948616 DOI: 10.1364/boe.7.002597] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 05/27/2016] [Accepted: 06/04/2016] [Indexed: 05/18/2023]
Abstract
The conjunctiva is a densely vascularized mucus membrane covering the sclera of the eye with a unique advantage of accessibility for direct visualization and non-invasive imaging. The purpose of this study is to apply an automated quantitative method for discrimination of different stages of diabetic retinopathy (DR) using conjunctival microvasculature images. Fine structural analysis of conjunctival microvasculature images was performed by ordinary least square regression and Fisher linear discriminant analysis. Conjunctival images between groups of non-diabetic and diabetic subjects at different stages of DR were discriminated. The automated method's discriminate rates were higher than those determined by human observers. The method allowed sensitive and rapid discrimination by assessment of conjunctival microvasculature images and can be potentially useful for DR screening and monitoring.
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Affiliation(s)
- Maziyar M Khansari
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - William O’Neill
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Richard Penn
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
- Department of Neurosurgery, Rush University and Hospital, Chicago, Illinois 60612, USA
| | - Felix Chau
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, 60612, USA
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, 60607, USA
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Felder AE, Wanek J, Blair NP, Shahidi M. Inner Retinal Oxygen Extraction Fraction in Response to Light Flicker Stimulation in Humans. Invest Ophthalmol Vis Sci 2016; 56:6633-7. [PMID: 26469748 DOI: 10.1167/iovs.15-17321] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Light flicker has been shown to stimulate retinal neural activity, increase blood flow, and alter inner retinal oxygen metabolism (MO2) and delivery (DO2). The purpose of the study was to determine the change in MO2 relative to DO2 due to light flicker stimulation in humans, as assessed by the inner retinal oxygen extraction fraction (OEF). METHODS An optical imaging system, based on a modified slit lamp biomicroscope, was developed for simultaneous measurements of retinal vascular diameter (D) and oxygen saturation (SO2). Retinal images were acquired in 20 healthy subjects before and during light flicker stimulation. Arterial and venous D (DA and DV) and SO2 (SO2A and SO2V) were quantified within a circumpapillary region. Oxygen extraction fraction was defined as the ratio of MO2 to DO2 and was calculated as (SO2A - SO2V)/SO2A. Reproducibility of measurements was assessed. RESULTS Coefficients of variation and intraclass correlation coefficients of repeated measurements were <5% and ≥0.83, respectively. During light flicker stimulation, DA, DV , and SO2V significantly increased (P ≤ 0.004). Oxygen extraction fraction was 0.37 ± 0.08 before light flicker and significantly decreased to 0.31 ± 0.07 during light flicker (P = 0.001). CONCLUSIONS Oxygen extraction fraction before and during light flicker stimulation is reported in human subjects for the first time. Oxygen extraction fraction decreased during light flicker stimulation, indicating the change in DO2 exceeded that of MO2. This technology is potentially useful for the detection of changes in OEF response to light flicker in physiological and pathological retinal conditions.
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Blair NP, Wanek J, Teng PY, Shahidi M. The effect of intravitreal vascular endothelial growth factor on inner retinal oxygen delivery and metabolism in rats. Exp Eye Res 2015; 143:141-7. [PMID: 26518179 DOI: 10.1016/j.exer.2015.09.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 09/15/2015] [Accepted: 09/29/2015] [Indexed: 02/08/2023]
Abstract
Vascular endothelial growth factor (VEGF) is stimulated by hypoxia and plays an important role in pathologic vascular leakage and neovascularization. Increased VEGF may affect inner retinal oxygen delivery (DO2) and oxygen metabolism (MO2), however, quantitative information is lacking. We tested the hypotheses that VEGF increases DO2, but does not alter MO2. In 10 rats, VEGF was injected intravitreally into one eye, whereas balanced salt solution (BSS) was injected into the fellow eye, 24 h prior to imaging. Vessel diameters and blood velocities were determined by red-free and fluorescent microsphere imaging, respectively. Vascular PO2 values were derived by phosphorescence lifetime imaging of an intravascular oxyphor. Retinal blood flow, vascular oxygen content, DO2 and MO2 were calculated. Retinal arterial and venous diameters were larger in VEGF-injected eyes compared to control eyes (P < 0.03), however no significant difference was observed in blood velocity (P = 0.21). Thus, retinal blood flow was greater in VEGF-injected eyes (P = 0.007). Retinal vascular PO2 and oxygen content were similar between control and VEGF-injected eyes (P > 0.11), while the arteriovenous oxygen content difference was marginally lower in VEGF-injected eyes (P = 0.05). DO2 was 950 ± 340 and 1380 ± 650 nL O2/min in control and VEGF-injected eyes, respectively (P = 0.005). MO2 was 440 ± 150 and 490 ± 190 nL O2/min in control and VEGF-injected eyes, respectively (P = 0.31). Intravitreally administered VEGF did not alter MO2 but increased DO2, suggesting VEGF may play an offsetting role in conditions characterized by retinal hypoxia.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
| | - Pang-yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA; UCLA Radiological Sciences, Suite 650, 924 Westwood Boulevard, Los Angeles, CA 90024, USA.
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
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Teng PY, Wanek J, Blair NP, Shahidi M. Response of inner retinal oxygen extraction fraction to light flicker under normoxia and hypoxia in rat. Invest Ophthalmol Vis Sci 2014; 55:6055-8. [PMID: 25183761 DOI: 10.1167/iovs.13-13811] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Oxygen extraction fraction (OEF), defined by the ratio of oxygen metabolism (MO2) to delivery (DO2), determines the level of compensation of MO2 by DO2. In the current study, we tested the hypothesis that inner retinal OEF remains unchanged during light flicker under systemic normoxia and hypoxia in rats due to the matching of MO2 and DO2. METHODS Retinal vascular oxygen tension (PO2) measurements were obtained in 10 rats by phosphorescence lifetime imaging. Inner retinal OEF was derived from vascular PO2 based on Fick's principle. Measurements were obtained before and during light flicker under systemic normoxia and hypoxia. The effects of light flicker and systemic oxygenation on retinal vascular PO2 and OEF were determined by ANOVA. RESULTS During light flicker, retinal venous PO2 decreased (P < 0.01, N = 10), while inner retinal OEF increased (P = 0.02). Under hypoxia, retinal arterial and venous PO2 decreased (P < 0.01), while OEF increased (P < 0.01). The interaction effect was not significant on OEF (P = 0.52), indicating the responses of OEF to light flicker were similar under normoxia and hypoxia. During light flicker, OEF increased from 0.46 ± 0.13 to 0.50 ± 0.11 under normoxia, while under hypoxia, OEF increased from 0.67 ± 0.16 to 0.74 ± 0.14. CONCLUSIONS Inner retinal OEF increased during light flicker, indicating the relative change in DO2 is less than that in MO2 in rats under systemic normoxia and hypoxia. Inner retinal OEF is a potentially useful parameter for assessment of the relative changes of MO2 and DO2 under physiologic and pathologic conditions.
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Affiliation(s)
- Pang-yu Teng
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Norman P Blair
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mahnaz Shahidi
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States
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Mezu-Ndubuisi OJ, Wanek J, Chau FY, Teng PY, Blair NP, Reddy NM, Raj JU, Reddy SP, Shahidi M. Correspondence of retinal thinning and vasculopathy in mice with oxygen-induced retinopathy. Exp Eye Res 2014; 122:119-22. [PMID: 24703909 DOI: 10.1016/j.exer.2014.03.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/05/2014] [Accepted: 03/25/2014] [Indexed: 11/30/2022]
Abstract
The aberrantly vascularized peripheral retina in retinopathy of prematurity (ROP) may be associated with visual field constriction, retinal dysfunction, and abnormalities in retinal thickness which is commonly assessed by spectral domain optical coherence tomography (SDOCT). However, due to the limitation of SDOCT for peripheral retinal imaging, retinal thickness in avascular peripheral retina in ROP has not been evaluated. Oxygen induced retinopathy (OIR) in mice has features of vasculopathy similar to those in human ROP. These features occur in the posterior retina and thereby are accessible by standard imaging methods. The purpose of the current study was to determine the correspondence between abnormalities in retinal thickness and vasculopathy in neonatal OIR mice by simultaneous SDOCT imaging and fluorescein angiography (FA). Newborn mice (N = 19; C57BL/6J strain) were exposed to 77% oxygen from postnatal day 7 (P7) to P12. Age-matched control mice (N = 12) were raised in room air. FA and SDOCT were performed in mice between P17 and P19 to visualize retinal vasculature and measure retinal thickness, respectively. Retinal thickness measurements in vascular regions of interest (ROIs) of control mice, and in hypovascular and avascular ROIs of OIR mice were compared. In control mice, FA showed uniformly dense retinal capillary networks between major retinal vessels and retinal thickness of vascular ROIs was 260 ± 7 μm (N = 12). In OIR mice, FA displayed hypovascular regions with less dense and fewer capillaries and avascular regions devoid of visible capillaries. Retinal thickness measurements of hypovascular and avascular ROIs were 243 ± 21 μm and 209 ± 11 μm (N = 19), respectively. Retinal thickness in hypovascular and avascular ROIs of OIR mice was significantly lower than in vascular ROIs of control mice (p ≤ 0.01). Likewise, retinal thickness in avascular ROIs was significantly lower than in hypovascular ROIs (p < 0.001). Retinal thinning in hypovascular and avascular regions may be due to arrested retinal development and/or ischemia induced apoptosis.
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Affiliation(s)
- Olachi J Mezu-Ndubuisi
- Departments of Pediatrics and Ophthalmology, University of Wisconsin School of Medicine and Public Health, 600 Highland Avenue, Madison, WI 53792, USA
| | - Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA
| | - Felix Y Chau
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA
| | - Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA
| | - Norman P Blair
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA
| | - Narsa M Reddy
- Department of Pediatrics, University of Illinois at Chicago, 840 S. Wood Street Chicago, IL 60612, USA
| | - J Usha Raj
- Department of Pediatrics, University of Illinois at Chicago, 840 S. Wood Street Chicago, IL 60612, USA
| | - Sekhar P Reddy
- Department of Pediatrics, University of Illinois at Chicago, 840 S. Wood Street Chicago, IL 60612, USA
| | - Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
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Abstract
PURPOSE The purpose of the study is to report global measurements of inner retinal oxygen delivery (DO2_IR) and oxygen metabolism (MO2_IR) in streptozotocin (STZ) diabetic rats. METHODS Phosphorescence lifetime and blood flow imaging were performed in rats 4 (STZ/4 wk; n = 10) and 6 (STZ/6 wk; n = 10) weeks following injection of STZ to measure retinal arterial (O2A) and venous (O2V) oxygen contents and total retinal blood flow (F). DO2_IR and MO2_IR were calculated from measurements of F and O2A and of F and the arteriovenous oxygen content difference, respectively. Data in STZ rats were compared to those in healthy control rats (n = 10). RESULTS Measurements of O2A and O2V were not significantly different among STZ/4 wk, STZ/6 wk, and control rats (P ≥ 0.28). Likewise, F was similar among all groups of rats (P = 0.81). DO2_IR measurements were 941 ± 231, 956 ± 232, and 973 ± 243 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.95). MO2_IR measurements were 516 ± 175, 444 ± 103, and 496 ± 84 nL O2/min in control, STZ/4 wk, and STZ/6 wk rats, respectively (P = 0.37). CONCLUSIONS Global inner retinal oxygen delivery and metabolism were not significantly impaired in STZ rats in early diabetes.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois
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Mezu-Ndubuisi OJ, Teng PY, Wanek J, Blair NP, Chau FY, Reddy NM, Raj JU, Reddy SP, Shahidi M. In vivo retinal vascular oxygen tension imaging and fluorescein angiography in the mouse model of oxygen-induced retinopathy. Invest Ophthalmol Vis Sci 2013; 54:6968-72. [PMID: 24052641 DOI: 10.1167/iovs.13-12126] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
PURPOSE Oxygenation abnormalities are implicated in the development of retinopathy of prematurity (ROP). The purpose of this study is to report in vivo retinal vascular oxygen tension (PO2) measurements and fluorescein angiography (FA) findings in the mouse model of oxygen-induced retinopathy (OIR). METHODS We exposed 19 neonatal mice to 77% oxygen from postnatal day 7 (P7) to P12 (OIR), while 11 neonatal mice were kept under room air (control). Using phosphorescence lifetime imaging, retinal vascular PO2 was measured followed by FA. Repeated measures ANOVA was performed to determine the effects of blood vessel type (artery and vein) and group (OIR and control) on PO2. Avascular retinal areas were measured from FA images in OIR mice. RESULTS There was a significant effect of vessel type on PO2 (P < 0.001). The effect of group on PO2 was not significant (P = 0.3), indicating similar PO2 between OIR and control mice. The interaction between group and vessel type was significant (P = 0.03), indicating a larger arteriovenous PO2 difference in OIR mice than control mice. In control mice, FA displayed normal vascularization, while FA of OIR mice showed abnormalities, including dilation and tortuosity of major retinal blood vessels, and avascular regions. In OIR mice, the mean percent avascular retinal area was 33% ± 18%. CONCLUSIONS In vivo assessment of retinal vascular oxygen tension and vascularization patterns demonstrated abnormalities in the mouse model of OIR. This approach has the potential to improve understanding of retinal vascular development and oxygenation alterations due to ROP and other ischemic retinal diseases.
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Abstract
PURPOSE Retinal hypoxia is a common pathological condition usually caused by ischemia that may result in alterations in oxidative energy metabolism. We report measurements of oxygen delivery by the retinal circulation (DO2_IR) and inner retinal oxygen metabolism (MO2_IR) under systemic normoxia and hypoxia in rat. METHODS Rats were ventilated with fractions of inspired oxygen (FiO2) to induce either normoxia (n = 10), moderate hypoxia (n = 14), or severe hypoxia (n = 10). Oxygen tension was measured in retinal vessels using phosphorescence lifetime imaging and converted to arterial (O2A) and venous (O2V) oxygen contents. Total retinal blood flow (F) was assessed by red-free and fluorescent microsphere imaging. DO2_IR and MO2_IR were calculated as the products of F and O2A, and F and the arteriovenous oxygen content difference (O2A-V), respectively. RESULTS Measurements of O2A, O2V, and O2A-V were significantly reduced with decreased FiO2 (P < 0.001). In response to reduced oxygen availability, F increased under moderate hypoxia (P < 0.001) but did not increase further under severe hypoxia (P = 0.5). DO2_IR was similar under normoxia and moderate hypoxia (P = 0.7), but significantly lower under severe hypoxia (P < 0.001). Likewise, MO2_IR under normoxia and moderate hypoxia was similar (P = 0.1), but significantly reduced under severe hypoxia (P ≤ 0.02). CONCLUSIONS DO2_IR and MO2_IR were maintained during moderate hypoxia, but reduced under severe hypoxia, indicating blood flow compensation became insufficient for the reduced oxygen availability. Future studies may aid our understanding of retinal metabolic function in ischemic conditions.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Abstract
PURPOSE Oxygen extraction fraction (OEF), defined by the ratio of oxygen consumption to delivery, may be a useful parameter for assessing the retinal tissue status under impaired circulation. We report a method for measurement of inner retinal OEF in rats under normoxia and hypoxia based on vascular oxygen tension (PO(2)) imaging. METHODS Retinal vascular PO(2) measurements were obtained in 10 rats, using our previously developed optical section phosphorescence lifetime imaging system. Inner retinal OEF was derived from retinal vascular PO(2) measurements based on Fick's principle. Measurements of inner retinal OEF obtained under normoxia were compared between nasal and temporal retinal sectors and repeatability was determined. Inner retinal OEF measurements obtained under normoxia and hypoxia were compared. RESULTS Retinal vascular PO(2) and inner retinal OEF measurements were repeatable (ICC ≥ 0.83). Inner retinal OEF measurements at nasal and temporal retinal sectors were correlated (R = 0.71; P = 0.02; n = 10). Under hypoxia, both retinal arterial and venous PO(2) decreased significantly as compared with normoxia (P < 0.001; n = 10). Inner retinal OEF was 0.46 ± 0.13 under normoxia and increased significantly to 0.67 ± 0.16 under hypoxia (mean ± SD; P < 0.001; n = 10). CONCLUSIONS Inner retinal OEF is a promising quantitative biomarker for the adequacy of oxygen supply for metabolism under physiologically and pathologically altered conditions.
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Affiliation(s)
- Pang-yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, USA
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Teng PY, Blair NP, Wanek J, Shahidi M. Oxygen tension and gradient measurements in the retinal microvasculature of rats. Graefes Arch Clin Exp Ophthalmol 2011; 250:361-7. [PMID: 22101835 DOI: 10.1007/s00417-011-1859-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 09/20/2011] [Accepted: 11/02/2011] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Oxygen delivery from the retinal vasculature plays a crucial role in maintaining normal retinal metabolic function. Therefore, measurements of retinal vascular oxygen tension (PO(2)) and PO(2) longitudinal gradients (gPO(2)) along retinal blood vessels may help gain fundamental knowledge of retinal physiology and pathological processes. METHODS Three-dimensional retinal vascular PO(2) maps were generated in rats by optical section phosphorescence lifetime imaging. A major retinal artery and vein pair, and a smaller blood vessel (microvessel) between them were segmented, and PO(2) along each blood vessel was measured. In each blood vessel, an average PO(2) (mPO(2)) was calculated, and gPO(2) was determined by linear regression analysis. Reproducibility of measurements was assessed by calculating intraclass correlation coefficient (ICC) of repeated measurements. The correlations of mPO(2) and gPO(2) measurements with systemic arterial oxygen tension (P(a)O(2)) and carbon dioxide tension (P(a)CO(2)) was determined. RESULTS Measurements of mPO(2) and gPO(2) in retinal arteries, microvessels and veins were reproducible (ICC > 0.86; p < 0.01; N = 8), except for retinal arterial gPO(2). Retinal arterial, microvessel and venous mPO(2) were 41 ± 8, 32 ± 8 and 25 ± 7 mmHg, respectively (mean ± SD; N = 27). Retinal arterial mPO(2) was correlated with P(a)O(2) and P(a)CO(2) (R > 0.44; p < 0.03), while retinal microvessel and venous mPO(2) were only correlated with P(a)CO(2) (R > 0.68; p < 0.01). Retinal microvessel gPO(2) (-3.8 ± 1.5 mmHg/100 μm) was significantly steeper (more negative) than venous gPO(2) (0.02 ± 0.43 mmHg/100 μm) (p < 0.01; N = 27), and neither were significantly correlated with P(a)O(2) or P(a)CO(2). CONCLUSIONS Quantitative measurement of mPO(2) and gPO(2) in the retinal microvasculature was demonstrated. A significant decrease in PO(2) was observed along most retinal microvessels, indicative of substantial oxygen extraction by the retinal tissue. This method has the potential to help elucidate retinal microvascular oxygen transport in health and disease.
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Affiliation(s)
- Pang-Yu Teng
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA
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Abstract
PURPOSE Since the metabolic function of the retinal tissue is altered due to physiologic changes or disease, measurements of outer retinal oxygen consumption (Q(OR)) may be beneficial in assessment of retinal status. The purpose of this study was to report measurements of Q(OR) in rats using a phosphorescence lifetime imaging technique. METHODS Phosphorescence lifetime imaging was performed and retinal PO(2) maps were generated in 10 rats under a light-adapted condition. Depth-resolved retinal PO(2) profiles were derived from the PO(2) maps. From the profiles, the maximum outer retina PO(2) (P(max)O(2)) was obtained and Q(OR) was calculated using a one-dimensional oxygen diffusion model. Repeatability, inter-location variability, and inter-subject variability of P(max)O(2) and Q(OR) measurements were established. RESULTS Intraclass correlation coefficients of repeated measurements of P(max)O(2) and Q(OR) were 0.89 and 0.70, respectively (P < 0.001). Inter-location variability of P(max)O(2) and Q(OR) measurements at superior to inferior contiguous locations on the retina were on average 9 mmHg and 0.22 ml O(2)/100 g-tissue-min, respectively. Mean and standard deviation of P(max)O(2) and Q(OR) measurements averaged over all rats were 60 ± 16 mmHg and 0.73 ± 0.28 ml O(2)/100 g-tissue-min, respectively. Inter-subject variability of P(max)O(2) and Q(OR) measurements was on average 2.3 and 1.5 times inter-location variability, respectively. CONCLUSIONS Measurements of outer retinal oxygen consumption can be made by phosphorescence lifetime imaging and may be of potential value for detecting changes in retinal oxygen metabolic activity due to altered physiological and pathological conditions over multiple locations and time points.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, Chicago, IL 60612, USA
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Wanek J, Teng PY, Albers J, Blair NP, Shahidi M. Inner retinal metabolic rate of oxygen by oxygen tension and blood flow imaging in rat. Biomed Opt Express 2011; 2:2562-8. [PMID: 21991548 DOI: 10.1364/boe.2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 07/29/2011] [Accepted: 07/29/2011] [Indexed: 05/10/2023]
Abstract
The metabolic function of inner retinal cells relies on the availability of nutrients and oxygen that are supplied by the retinal circulation. Assessment of retinal tissue vitality and function requires knowledge of both the rate of oxygen delivery and consumption. The purpose of the current study is to report a novel technique for assessment of the inner retinal metabolic rate of oxygen (MO(2)) by combined measurements of retinal blood flow and vascular oxygen tension (PO(2)) in rat. The application of this technology has the potential to broaden knowledge of retinal oxygen dynamics and advance understanding of disease pathophysiology.
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Affiliation(s)
- Justin Wanek
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago IL, 60612, USA
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Abstract
PURPOSE To report an imaging technique for measurement of oxygen tension (PO2) in retinal tissue and establish its feasibility for measuring retinal PO2 variations in rat eyes by adjusting the fraction of inspired oxygen (FiO2). METHODS A narrow laser line was projected at an angle on the retina, and phosphorescence emission was imaged after intravitreal injection of an oxygen-sensitive molecular probe. A frequency-domain approach was used for phosphorescence lifetime measurements. Retinal PO2 maps were computed from phosphorescence lifetime images, and oxygen profiles through the retinal depth were derived in rats in conditions of 10%, 21%, and 50% FiO2. RESULTS Retinal PO2 measurements were repeatable, and variations in outer and inner retina PO2 at different locations along the image were not significant (P>or=0.3). Maximum outer retinal PO2 obtained in 10%, 21%, and 50% FiO2 were significantly different (P<0.0001). Maximum outer retinal PO2 correlated with systemic arterial PO2 (R=0.70; P<0.0001). The slope of the outer retina PO2 profile correlated with maximum outer retinal PO2 (R=0.84; P<0.0001). Mean inner retina PO2 correlated with maximum outer retinal PO2 (R=0.88; P<0.0001). CONCLUSIONS A technique has been developed for quantitative mapping of retinal tissue oxygen tension with the potential to enable sequential monitoring of retinal oxygenation in health and disease.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Blair MP, Gupta M, Blair NP, Shahidi M. Association Between Retinal Thickness and Retinal Pigment Epithelium Elevation in Age-Related Macular Degeneration. Ophthalmic Surg Lasers Imaging Retina 2010; 41:175-81. [DOI: 10.3928/15428877-20100303-04] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2009] [Indexed: 11/20/2022]
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Blair NP, Wanek JM, Mori M, Shahidi M. Abnormal retinal vascular oxygen tension response to light flicker in diabetic rats. Invest Ophthalmol Vis Sci 2009; 50:5444-8. [PMID: 19553624 DOI: 10.1167/iovs.09-3465] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To test the hypothesis that the intravascular oxygen response to light flicker is abnormal in diabetes. METHODS Ten eyes of normal rats and 10 eyes of rats made diabetic with streptozotocin were examined. Oxygen tension (PO(2)) was measured noninvasively in the retinal arteries and veins on optical section retinal images. PO(2) was estimated based on the quenching by oxygen of the phosphorescence of an intravenously injected palladium porphyrin molecular probe. Measurements were conducted with and without light flicker at 10 Hz. Oxygen saturation (SO(2)) was calculated with adjustment for the arterial pH. RESULTS In the normal rats flicker induced an increase in arterial PO(2) and in the difference in arterial and venous (A-V difference) PO(2) from 51 +/- 5 (mean and SD) to 55 +/- 7 mm Hg and from 22 +/- 3 to 26 +/- 5 mm Hg, respectively (P < 0.002 and 0.015, respectively). Flicker induced an increase of arterial SO(2) and A-V SO(2) difference from 64% +/- 8% to 68% +/- 7% and from 34% +/- 4% to 38% +/- 6%, respectively (P < 0.002 and 0.035, respectively). No changes in PO(2) or SO(2) were observed with flicker in the veins. In the diabetic rats, no significant flicker-induced changes were seen in PO(2) or SO(2) in the retinal arteries, veins, or A-V differences. CONCLUSIONS The diabetic rats lacked the flicker induced increase in arterial PO(2) and SO(2) and also the A-V difference in PO(2) and SO(2) observed in the normal rats. The best explanation appeared to be that diabetes impairs the increase in oxygen consumption normally provoked by light flicker.
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Affiliation(s)
- Norman P Blair
- Department of Ophthalmology and Visual Sciences; University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Abstract
PURPOSE An optical section phosphorescence lifetime imaging system was developed for three-dimensional mapping of oxygen tension (P(O2)) in chorioretinal vasculatures. METHODS A laser line was projected at an oblique angle and scanned on the retina after intravenous injection of an oxygen-sensitive molecular probe to generate phosphorescence optical section images. An automated software algorithm segmented and combined images from spatially adjacent locations to construct depth-displaced en face retinal images. Intravascular P(O2) was measured by determining the phosphorescence lifetime. Three-dimensional chorioretinal P(O2) maps were generated in rat eyes under varying fractions of inspired oxygen. RESULTS Under an air-breathing condition, mean P(O2) in the choroid, retinal arteries, capillaries, and veins were 58+/-2 mm Hg, 47+/-2 mm Hg, 44+/-2 mm Hg, and 35+/-2 mm Hg, respectively. The mean arteriovenous P(O2) difference was 12+/-2 mm Hg. With a lower fraction of inspired oxygen, chorioretinal vascular P(O2) and mean arteriovenous P(O2) differences decreased compared with measurements under an air-breathing condition. Retinal venous P(O2) was statistically lower than P(O2) measured in the retinal artery, capillaries, and choroid (P<0.004). CONCLUSIONS Three-dimensional mapping of chorioretinal oxygen tension allowed quantitative P(O2) measurements in large retinal blood vessels and in retinal capillaries. This method has the potential to facilitate better understanding of retinal oxygenation in health and disease.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Abstract
PURPOSE To investigate oxygen tension (P(O2)) changes in the retinal and choroidal vasculatures in response to visual stimulation by light flicker. METHODS A previously developed optical section phosphorescence imaging system was used to measure P(O2) separately in the retinal veins, arteries, and capillaries and in the choroid before and during light flicker. Imaging was performed in rats during light flicker at frequencies between 0 and 14 Hz. Light flicker-induced changes in the chorioretinal vasculature P(O2) and arteriovenous P(O2) differences were determined. Retinal arterial and venous P(O2) were measured along blood vessels as a function of the distance from the optic nerve head. RESULTS Retinal arterial P(O2) and arteriovenous P(O2) differences increased with increasing light flicker at frequencies up to 10 Hz, after which no further increase was observed. Significant increases in retinal arterial P(O2) (P = 0.009; n =10) and in retinal capillary P(O2) (P = 0.04, n = 10) were measured in response to light flicker at 10 Hz. Retinal arteriovenous P(O2) differences during light flicker were significantly greater than differences before light flicker (P = 0.01; n = 10). Retinal arterial P(O2) decreased significantly with increased distance from the optic nerve head (P < or = 0.004), whereas retinal venous P(O2) remained relatively unchanged (P > or= 0.4). CONCLUSIONS Measurement of changes in the chorioretinal vasculature P(O2) can potentially advance the understanding of oxygen dynamics in challenged physiological states and in animal models of human retinal diseases.
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Affiliation(s)
- Akbar Shakoor
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago (UIC), 1855 West Taylor Street, Chicago, IL 60612, USA
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Abstract
PURPOSE To report an optical imaging system that was developed to measure oxygen tension (pO2) in the chorioretinal vasculatures. The feasibility of the system for the measurement of changes in pO2 separately in the retinal and choroidal vasculatures was established in rat eyes by varying the fraction of inspired oxygen and inhibiting nitric oxide activity. METHODS Our optical section phosphorescence imaging system was modified to provide quantitative measurements of pO2 separately in the retinal and choroidal vasculatures. A narrow laser line was projected at an angle on the retina after intravenous injection of an oxygen-sensitive probe (Pd-porphyrin), and phosphorescence emission was imaged. A frequency-domain approach allowed measurements of the phosphorescence lifetime by varying the phase relationship between the modulated excitation laser light and sensitivity of the imaging camera. Chorioretinal pO2 was measured while varying the fraction of inspired oxygen and during intravenous infusion of Nomega-nitro-L-arginine (Nomega-NLA), a nonselective nitric oxide synthase inhibitor. RESULTS The systemic arterial pO2 varied according to the fraction of inspired oxygen. The pO2 in the retinal and choroidal vasculatures increased as the fraction of inspired oxygen was increased. Compared with baseline, choroidal pO2 decreased during infusion of Nomega-NLA, whereas the pO2 in the retinal vasculatures remained relatively unchanged. The choroidal pO2 decreased markedly with each incremental increase in Nomega-NLA infusion rate, in the range 1-6 mg/min, and there was no additional change in the choroidal pO2 at Nomega-NLA infusion rates above 6 mg/min. CONCLUSIONS An optical method combining pO2 phosphorescence imaging with chorioretinal optical sectioning was established that can potentially be applied for better understanding of retinal and choroidal oxygen dynamics in physiologic and pathologic states.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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Abstract
PURPOSE To report the feasibility of retinal thickness mapping for evaluating thickness differences in retinal areas with and without leakage shown by fluorescein angiography for patients who have age-related macular degeneration with choroidal neovascularization. METHODS A custom-built version of the retinal thickness analyzer was used for thickness mapping. Retinal thickness was defined as the separation between vitreoretinal and pigment epithelium-choroid interfaces. Imaging was performed in 1 eye of 10 patients with the clinical diagnoses of age-related macular degeneration and choroidal neovascularization. Patients either had never undergone photodynamic therapy at the time of measurement (untreated) or had received one or more photodynamic therapy treatments (treated). Average retinal thicknesses in selected areas with and without the presence of leakage shown by fluorescein angiography were calculated and compared statistically. RESULTS Retinal thickness (mean +/- SD) in areas with leakage (315 +/- 54 microm) was significantly greater than that in areas without leakage (280 +/- 28 microm) (P = 0.03). In untreated patients, areas with leakage (345 +/- 45 microm) were significantly thicker than areas without leakage (289 +/- 23 microm) (P = 0.02). In treated patients, retinal thickness in areas with leakage (271 +/- 33 microm) and without leakage (267 +/- 34 microm) was similar. CONCLUSION Retinal thickness mapping may prove to be useful as an adjunct to fluorescein angiography to monitor choroidal neovascularization and its treatment.
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Affiliation(s)
- A Shakoor
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, USA
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Abstract
PURPOSE To demonstrate the capability of our optical imaging system to assess oxygenation changes in chorioretinal vasculatures due to experimentally induced carotid occlusion. METHODS Chorioretinal oxygenation was assessed by projecting a narrow laser line at an angle on the retina after intravenous injection of an oxygen sensitive probe and imaging phosphorescence emission. Optical section phosphorescence imaging was performed in rats, under steady-state conditions and during unilateral occlusion of the common carotid artery. Phosphorescence intensity was measured in the retinal vein, artery, capillaries, and choroid vascular areas. Oxygenation was defined as the inverse of phosphorescence intensity. Oxygenation changes in the four vascular areas were determined relative to initial preocclusion oxygenation values and compared to measured changes under steady-state conditions. RESULTS Under steady-state conditions, phosphorescence intensity in chorioretinal vasculatures remained constant, displaying a change of < or = 8% over time. At 12 +/- 5 s from initiation of occlusion, oxygenation decreased in the retinal venous, arterial, capillary, and choroidal circulations by -41 +/-19%, -10 +/- 5%, -20 +/- 18%, -10 +/- 5%, respectively (p < or = 0.05; n = 6). At 30 +/- 10 s from initiation of occlusion, oxygenation change in the retinal vein, artery, capillaries, and choroid was -9 +/- 12%, -2 +/- 4%, -11 +/- 21%, -1 +/- 8%, respectively, and not statistically different as compared to steady-state oxygenation changes (p > or = 0.3; n = 6). CONCLUSIONS Optical section phosphorescence imaging technique can be used to assess intravascular oxygenation changes and may be a valuable tool for studying disease-related oxygen dynamics in the chorioretinal vasculatures.
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Affiliation(s)
- Akbar Shakoor
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Szlyk JP, Vajaranant TS, Rana R, Lai WW, Pulido JS, Paliga J, Blair NP, Seiple W. Assessing Responses of the Macula in Patients with Macular Holes using a New System Measuring Localized Visual Acuity and the mfERG. Doc Ophthalmol 2005; 110:181-91. [PMID: 16328926 DOI: 10.1007/s10633-005-4313-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2005] [Indexed: 11/30/2022]
Abstract
PURPOSE To evaluate acuity and multifocal electroretinogram (mfERG) responses from the macula in affected and unaffected fellow eyes of patients with macular holes. METHODS We tested 10 eyes with macular hole and 10 fellow eyes from 11 patients. We measured local visual acuity thresholds at 27 discrete locations within 21 degrees diameter using the Functional Fundus Imaging System (FFIS), a psychophysical system that measures visual acuity as a function of visual field location, and local ERG responses within 45 degrees diameter using the mfERG. RESULTS In the affected eyes, the mean FFIS visual acuity thresholds were significantly elevated within the central 21 degrees diameter area, compared to a group of control eyes. No significant differences were found between the acuities of the fellow eyes compared to those of the control group. The amplitudes of the first positive peak of the mfERG were reduced in the central 7.8 degrees in affected eyes. In the central 2 degrees , 4 out of 10 affected eyes showed non-measurable ERG signals. The remaining six eyes showed significantly reduced mean amplitudes, but not delayed implicit times, when compared to the control group. For the fellow eyes, the mean amplitudes of the mfERG and implicit times did not differ from the means of the control eyes. CONCLUSIONS Both local psychophysical and electrophysiological testing demonstrated retinal dysfunction extending beyond the site of the macular holes in some patients (three of the patients had central mfERG amplitudes falling within the normal range).
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Affiliation(s)
- Janet P Szlyk
- Research and Development Service, Jesse Brown Department of Veterans Affairs Medical Center, Chicago, IL, USA
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Abstract
PURPOSE To investigate differences in higher-order ocular aberrations and in optical section retinal image resolution between healthy normal and diabetic subjects. METHODS An optical imaging system was established for combined retinal optical section imaging and wavefront sensing. A laser beam was expanded and focused to a point on the retina by the optics of the eye. For optical section retinal imaging, a cylindrical lens was placed in the path of the incident laser beam to form a focused line on the retina. Because of the angle between the incident laser and imaging path, an optical section image of the retina was captured. For wavefront sensing, a Shack-Hartmann aberrometer was incorporated in the imaging system. Twenty-two subjects with diabetes (average age, 52 +/- 12 years) and 13 normal subjects (average age, 47 +/- 9 years) were imaged. Retinal depth resolution was determined from the width of the laser line on the retina. Higher-order ocular aberrations were determined from the root mean square of the third to seventh Zernike terms, characterizing the wavefront aberration function. The data were analyzed statistically using Student's t-test and linear regression. RESULTS Higher-order ocular aberrations in diabetic subjects were significantly higher than in normal subjects (p=0.03). The retinal image depth resolution in diabetic subjects was significantly lower than in normal subjects (p <0.001). The retinal image depth resolution was inversely correlated with higher-order aberrations (r=-0.5; p=0.007; N=35). CONCLUSIONS The results demonstrate disease-related increases in higher-order ocular aberrations that influence retinal image resolution in diabetic eyes. This information is useful for designing high-resolution retinal imaging systems applicable for eyes with retinal disease.
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Affiliation(s)
- Mahnaz Shahidi
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
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