Relationship between the morphology of the foveal avascular zone, retinal structure, and macular circulation in patients with diabetes mellitus

Optical coherence tomography angiography measurements in systemic lupus erythematosus: A systematic review and meta-analysis

Systemic lupus erythematosus (SLE) is an autoimmune disease affecting various organs. Ocular involvement, particularly retinopathy, is common, emphasizing the significance of early detection. Optical coherence tomography angiography (OCTA), a non-invasive imaging technique, reveals microvascular changes, aiding SLE diagnosis and monitoring. This study evaluates OCTA's effectiveness in detecting SLE-related retinal alterations. A systemic search was undertaken across PubMed, Embase, and Scopus databases to identify studies presenting OCTA measurements in SLE patients compared to healthy controls. The meta-analysis, employing either fixed-effects or random-effects models based on heterogeneity levels, was conducted. Additionally, subgroup and sensitivity analyses, meta-regression, and quality assessments were carried out. Thirteen studies of 565 eyes in the SLE group, and 560 eyes in the control group were included. The meta-analyses revealed that SLE patients had a significantly lower retinal vessel density in the superficial and deep capillary plexus layers, choriocapillaris flow area, and foveal avascular zone (FAZ) circularity index compared to healthy controls, but that there were no significant differences in the FAZ area and perimeter. These findings highlight how OCTA can provide a noninvasive assessment of SLE effects on the retinal microvasculature, potentially presenting a reliable biomarker for more precise detection of SLE and disease activity monitoring.

Retinal and Choroidal Vascularity Evaluation in Pediatric Radiologically Isolated Syndrome and Multiple Sclerosis

BACKGROUND

To assess vessel density (VD) and flow of retinal plexuses and peripapillary region related with the pediatric radiologically isolated syndrome (RIS) and multiple sclerosis (MS).

METHODS

We analyzed 24 eyes of 12 participants with the diagnosis of RIS, 24 eyes of 12 participants with the diagnosis of MS, and 26 eyes of 13 age- and sex-matched healthy controls in this prospective, cross-sectional study. The superficial capillary plexus (SCP) and deep capillary plexus, foveal avascular zone, and the flow of choriocapillaris were investigated using optical coherence tomography angiography.

RESULTS

Parafoveal VD and all subregion parameters in SCP were significantly decreased in the MS group compared with the controls, whereas only nasal and inferior VD were significantly decreased in the pediatric RIS group compared with the controls. Ganglion cell layer (GCL) thickness of all subregions of the inner ring was significantly decreased in the pediatric MS group compared with the control group. No significant difference was observed between the pediatric RIS group and the control group regarding thickness.

CONCLUSIONS

We showed lower parafoveal VD in all subregions of SCP in pediatric MS, whereas only parafoveal nasal and inferior VD were decreased in pediatric RIS. GCL thickness of inner ring was significantly decreased in the pediatric MS, whereas GCL thickness did not change in pediatric RIS. Therefore, a decrease of parafoveal nasal and inferior VD without a decrease in thickness implies an early impairment of microvasculature in the RIS before impairment of thickness and that microvascular alterations begin from highly vascular superficial parafovea.

Reduced Vessel Density and Enlarged Foveal Avascular Zone in the Macula as a Result of Systemic Hypoxia Caused by SARS-CoV-2 Infection

Infection with SARS-CoV-2 can lead to various long-term consequences, including those of an ophthalmic nature. This paper reviews the results of optical coherence tomography angiography (OCTA) performed among COVID-19 patients. The review included papers evaluating short- and long-term outcomes following the SARS-CoV-2 infection. Some differentiated the obtained retinal and choroidal vascularization parameters according to gender. Following COVID-19, patients reveal changes in retinal and choroidal vascular parameters based on OCTA, such as reduced vascular density and an increased foveal avascular zone, which can persist for several months. Routine ophthalmic follow-up with OCTA should be considered in patients after SARS-CoV-2 infection to assess the effects of inflammation and systemic hypoxia in COVID-19. Further research is needed to understand whether infection with particular viral variants/subvariants may vary in the risk of effects on retinal and choroidal vascularization and whether and to what extent these risks may also differ in relation to reinfected and vaccinated individuals.

Long-Term Effect of SARS-CoV-2 Infection on the Retinal and Choroidal Microvasculature

The purpose of this study was to evaluate the persistent changes in microvascular parameters based on optical coherence tomography angiography (OCTA) in patients hospitalized due to COVID-19 bilateral pneumonia. The case-control prospective study was carried out among 49 patients with COVID-19 and 45 healthy age- and gender-matched 2 and 8 months after hospital discharge. We found a significantly decreased vessel density (VD) in superficial capillary plexus (SCP) in COVID-19 patients. Significantly decreased vessel density (VD) in the superficial capillary plexus (SCP), the deep capillary plexus (DCP), and choriocapillaris (CC), with significantly increased vessel density observed in the choriocapillaris in the foveal area (FCC). The foveal avascular zone in DCP (FAZd) was significantly increased in the COVID-19 group. We found differences between OCTA parameters according to gender. The foveal VD in SCP and DCP was significantly decreased in women compared to men. The FAZ area in SCP (FAZs) and superior VD in the choriocapillaris (SCC) were significantly increased in women. In conclusion, we noticed persistent changes in the ocular parameters of OCTA in COVID-19 patients. At the second follow-up visit, we observed a widened FAZ zone in SCP and decreased VD in some regions of the retina and choroid.

Evaluation of parafoveal and peripapillary vascular densities using optical coherence tomography angiography in children with thalassemia major

Background:

Thalassemia major (TM) is an inherited anaemia caused by faulty haemoglobin synthesis. Reducing serum iron levels using iron chelating agents is an important step in the treatment of TM, and the effects on the eye of both the disease and these agents can be determined by regular eye examination.

Objectives:

We evaluated macular and optic nerve vascular densities in children with TM and compared the results with healthy controls using optical coherence tomography angiography (OCTA).

Design:

This is a prospective study.

Methods:

A total of 30 children with TM and 30 healthy controls were included in the study. The area of the foveal avascular zone (FAZ) and the vascular densities (VD) of the optic nerve head (ONH), radial peripapillary capillary (RPC) and deep and superficial retinal vascular networks were measured using OCTA.

Results:

A statistically significant decrease in VD was observed in the whole image and the parafovea, superior hemi, superior and inferior parts of the superficial capillary plexus and in the whole image and the superior regions of the deep capillary plexus in the TM patient group compared with the control group ( p < 0.05). A significant decrease in VD was also observed in the whole image and the inside disc, peripapillary, nasal, inferonasal and temporal regions of the ONH and in the whole image and the inside disc, peripapillary and inferonasal regions of the RPC network in patients with TM ( p < 0.05). A significant positive correlation was observed between both serum ferritin levels and deferasirox dosage, on one hand, and both the superficial ( p = 0.023 and p = 0.002, respectively) and deep FAZs ( p = 0.015 and p = 0.045, respectively), on the other hand. A negative correlation was also found between the deferasirox dosage and the VDs of the superficial ( p = 0.010) and deep ( p = 0.001) foveal plexuses.

Conclusion:

Retinal VD and FAZ are affected in patients with TM. OCTA, which can noninvasively measure retinal VD in patients with TM, may be a useful tool for the early detection of retinal microvascular changes that may occur during the course of the disease.

Correcting magnification error in foveal avascular zone area measurements of optical coherence tomography angiography images with estimated axial length

Background

To generate and validate a method to estimate axial length estimated (AL_est) from spherical equivalent (SE) and corneal curvature [keratometry (K)], and to determine if this AL_est can replace actual axial length (AL_act) for correcting transverse magnification error in optical coherence tomography angiography (OCTA) images using the Littmann-Bennett formula.

Methods

Data from 1301 participants of the Raine Study Gen2-20 year follow-up were divided into two datasets to generate (n = 650) and validate (n = 651) a relationship between AL, SE, and K. The developed formula was then applied to a separate dataset of 46 participants with AL, SE, and K measurements and OCTA images to estimate and compare the performance of AL_est against AL_act in correcting transverse magnification error in OCTA images when measuring the foveal avascular zone area (FAZA).

Results

The formula for AL_est yielded the equation: AL_est = 2.102K − 0.4125SE + 7.268, R² = 0.794. There was good agreement between AL_est and AL_act for both study cohorts. The mean difference [standard deviation (SD)] between FAZA corrected with AL_est and AL_act was 0.002 (0.015) mm² with the 95% limits of agreement (LoA) of − 0.027 to 0.031 mm². In comparison, mean difference (SD) between FAZA uncorrected and corrected with AL_act was − 0.005 (0.030) mm², with 95% LoA of − 0.064 to 0.054 mm².

Conclusions

AL_act is more accurate than AL_est and hence should be used preferentially in magnification error correction in the clinical setting. FAZA corrected with AL_est is comparable to FAZA corrected with AL_act, while FAZA measurements using images corrected with AL_est have a greater accuracy than measurements on uncorrected images. Hence, in the absence of AL_act, clinicians should use AL_est to correct for magnification error as this provides for more accurate measurements of fundus parameters than uncorrected images.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-022-00299-x.

The Effect of Reduced Oxygen Saturation on Retinal Microvascularization in COVID-19 Patients with Bilateral Pneumonia Based on Optical Coherence Tomography Study

The aim of the study was to evaluate changes in the retinal thickness and microvasculature based on optical coherence tomography (OCT) depending on baseline oxygen saturation (SpO2) in patients hospitalized due to COVID-19 bilateral pneumonia. The prospective study was carried out among 62 patients with COVID-19 pneumonia who underwent ophthalmic examination after hospital discharge. They were divided into three groups depending on the oxygen saturation (SpO2) on admission: ≤90% (group 1), >90% and ≤95% (group 2), and >95% (group 3). The following parameters were assessed in the ophthalmological examination and correlated with the baseline SpO2: ganglion cell layer (GCL), the retinal nerve fiber layer (RNFL) in the macular area, RNFL in the peripapillary area, the foveal avascular zone (FAZ) in superficial capillary plexus (SCP) and deep capillary plexus (DCP), vessel density (VD) in SCP, in DCP, and in the choriocapillaris plexus (CC). Baseline saturation ≤90% in COVID-19 patients caused a decrease of VD in some areas of SCP and DCP and an increase in FAZ area in SCP and DCP. In the group of patients with SpO2 ≤ 90% statistically significant thinning of the retina in the inner superior ring (ISR) (p = 0.029), the inner temporal ring (ITR) (p = 0.34), the outer superior ring (OSR) (p = 0.012), and the outer temporal ring (OTR) (p= 0.004)] was observed. The statistically significant thickening of RNFL optic disc and thinning of RNFL retina in some macular areas in patients with SpO2 ≤ 90% were reported. The size of FAZ area in SCP and vessel density were significantly greater in some areas of SCP, DCP, and CC in patients with SpO2 ≤ 90% (p = 0.025). Baseline oxygen saturation ≤90% has been found to influence the ocular parameters of OCT in COVID-19 patients. We noticed a widened FAZ zone in SCP and increased VD in some regions of the retina and choroid as a response to systemic hypoxia.

Subclinical Retinal Capillary Abnormalities in Juvenile Systemic Lupus Erythematosus without Ocular Involvement

PURPOSE

This study aimed to evaluate subclinical retinal microvascular changes with OCTA in juvenile systemic lupus erythematosus (JSLE) patients without ocular involvement.

METHODS

Ten eyes of 10 JSLE and 13 eyes of 13 age and sex-matched healthy controls (HCs) were enrolled. The superficial (SCP) and deep capillary plexus (DCP), FAZ parameters, the flow area of the outer retina, and choriocapillaris were evaluated using OCTA.

RESULTS

All vessel density (VD) parameters in DCP were significantly lower in JSLE group compared to HCs. There was no significant difference between the groups in VD parameters of both SCP and ONH, FAZ, outer retina and choriocapillaris flow area. All DCP VD parameters showed a good ability to differentiate JSLE from HCs.

CONCLUSION

OCTA could detect retinal vascular impairment in the deep macular region in JSLE patients with normal ocular examination. Furthermore, all DCP VD parameters have a good ability to discriminate JSLE from HCs.

Optical coherence tomography angiography analysis of changes in the foveal avascular zone in eyes with diabetic macular edema treated with intravitreal anti-vascular endothelial growth factor

Background

To analyze the changes in foveal avascular zone (FAZ) area, perimeter, and circularity in the superficial (SCP) and deep (DCP) capillary plexuses in eyes with diabetic macular edema (DME) treated with intravitreal anti-VEGF using optical coherence tomography angiography (OCTA).

Methods

This prospective observational study included 56 eyes from 32 patients with DME that received intravitreal anti-VEGF. OCTA images were obtained at baseline and 1, 3, and 6 months of follow-up. The outcome measures were FAZ area, perimeter, and circularity in both the SCP and DCP, as well as central subfield thickness (CST) and best-corrected visual acuity (BCVA).

Results

The mean number of intravitreal anti-VEGF injections received during the observation period was 4.60 ± 0.82 (range: 3–6). The FAZ area, perimeter, and circularity were statistically unchanged at all observation points in both the SCP (p = 0.772, p = 0.405, p = 0.157, respectively) and the DCP (p = 0.620, p = 0.769, p = 0.481, respectively). Despite having no change in the FAZ parameters, there was still a statistically significant decrease in CST (p < 0.001) as well as a statistically significant increase in BCVA (p = 0.004) during the observation period.

Conclusions

The FAZ area, perimeter, and circularity in the SCP and DCP as measured by OCTA remained stable during the first 6 months of intravitreal anti-VEGF therapy in eyes with DME. While there were no significant changes in the FAZ, treatment with intravitreal anti-VEGF still resulted in decreased CST and improved BCVA.

Effect of Mydriatic Administration On Retinal Hemodynamics in Glaucoma: An Optical Coherence Tomography Angiography Study

PRCIS

Pupillary dilation with 0.5% tropicamide and 2.5% phenylephrine resulted in a statistically significant decrease in foveal avascular zone (FAZ) metrics in glaucoma eyes. This observation emphasizes the critical role of pupillary status in interpreting glaucomatous vascular alterations detected by OCTA.

PURPOSE

To evaluate the influence of mydriatic eye drops on optical coherence tomography angiography (OCTA) parameters in patients with primary open-angle glaucoma (POAG).

METHODS

A total of 20 POAG eyes and 20 control eyes were recruited in the study. The imaging area on the fundus was visualized by AngioPlex (Cirrus 5000 HD-OCT; Carl Zeiss Meditec) using en face view of 3×3▒mm and 6×6▒mm preview scans. Images were generated before and after the instillation of topical 0.5% tropicamide and 2.5% phenylephrine. Optic nerve head (ONH) perfusion, ONH flux index, macular perfusion density, macular vessel density, and foveal avascular zone (FAZ) measurements were consecutively obtained for each session. Differences between the pre-and post-dilation measurements were evaluated in POAG patients and controls.

RESULTS

POAG eyes showed a statistically significant decrease in the FAZ area from a mean of 0.29▒mm2to 0.25▒mm2(P=0.037) and FAZ perimeter from a mean of 2.27▒mm to 2.09▒mm (P=0.045) in the OCTA 6×6▒mm scan area after tropicamide/phenylephrine instillation. Pre-and post-dilation measurements of ONH perfusion and ONH flux index were significantly lower in the glaucoma group compared to controls (P<0.05, for all).

CONCLUSION

Topical pupillary dilation with 0.5% tropicamide and 2.5% phenylephrine results in a statistically significant reduction in the FAZ area and FAZ perimeter in POAG eyes. Further OCTA studies are needed for the diagnostic value of vascular changes due to pupil dilation in glaucoma.

PRE-RETINOPATHY OF TYPE 1 DIABETES IN THE CONTEXT OF FUNCTIONAL, STRUCTURAL AND MICROCIRCULATORY CHANGES IN THE MACULAR AREA

AIM

The authors assessed the development of intraocular changes in type 1 diabetes (T1DM) from the onset of the disease leading to diabetic retinopathy (DR). The quote: &#8220;There must be an intermediate stage between the physiological intraocular finding and the diabetic retinopathy itself &#8220;, (prof. Jan Vav&#345;inec).

METHODS

A two-year study (2018 and 2019) was conducted at the Department of Ophthalmology of the Teaching Hospital Kralovske Vinohrady in Prague (Czech Republic). There were 54 patients aged 17-42 years, the detection of T1DM ranged between the 1st and 14th year of life, with a duration of 12-35 years. Individual patients were always examined simultaneously by three methods: CS (contrast sensitivity), SD-OCT (spectral domain optical coherence tomography) and OCT-A (optical coherence tomography-angiography). We examined 106 eyes once and in a comprehensive manner.

RESULTS

We have shown that there is an intermediate stage between the physiological finding on the retina and DR, so-called diabetic pre-retinopathy (DpR). Subsequent redistribution of the observed into two DpR subgroups was derived from the size of the FAZ, either with its smaller area or with a larger area determining the microvascularity of the central area of the retina. The results of both other methods were assigned to these values. For SD-OCT, the depth of the fovea (the difference between the central retinal thickness and the total average retinal thickness) was determined, which was affected by the increased the macular cubature. In all patients it was on average 10.3 &#956;m3. The retina in the central area was significantly strengthened compared to the healthy population at the level of significance p 0,001. We divided the actual DpR into an image: DpR1 in 26.5 % of eyes - condition with an average shallower fovea only by 21.5 &#956;m below the level of the surrounding retina and an average narrower FAZ: 0.165 mm2 and with a more significant decrease in CS; DpR2 in 40.5 % of eyes - condition with average deeper fovea by 42 &#956;m, i.e., more significantly and average larger FAZ: 0.325 mm2 with lower decrease of CS. At the same time, other changes in microvascularity were noted, such as disorders in the sense of non-perfusion in the central part of the retina of various degrees. This finding differed significantly from changes in already established (non-proliferative) NPDR in 36 % of eyes, when a significant decrease in CS with normal visual acuity was found 4/4 ETDRS. Statistical differences in CS between DpR1 and DpR2 and NPDR were determined - always p 0.001. The average depth of the fovea was NPDR: 29.5 &#956;m. NPDR had the largest average FAZ: 0.56 mm2. Also significant were the most significant changes in non-perfusion and especially the presence of microaneurysms.

CONCLUSIONS

These three non - invasive methods helped to monitor the dynamics of the development of ocular changes in T1DM of better quality than the determination of visual acuity and ophthalmoscopic examination. Increased retinal volume induced hypoxia of visual cells with subsequent dual autoregulatory mechanism conditioning two types of diabetic pre-retinopathy before the onset of DR.

Macular microvascular changes in children with transfusion-dependent beta-thalassemia

BACKGROUND

To investigate the effect of iron overload on macular perfusion among transfusion-dependent thalassemia (TDT) patients using optical coherence tomography angiography (OCTA) METHODS: The study is a prospective observational case-control study. It included 27 eyes from 27 children with transfusion-dependent β-thalassemia and 25 eyes from 25 age-matched controls. All participants were evaluated clinically and with OCTA Avanti RTVue-XR system (Optovue) to assess macular microvascular changes, by measuring vessels density (VDs) and foveal avascular zone (FAZ) area, at both superficial and deep retinal plexuses and at choriocapillaris level.

RESULTS

Foveal and parafoveal zones were significantly thinner among thalassemia patients, with significantly larger FAZ area at the level of both superficial and deep retinal plexuses when compared with control group. The thalassemia group showed significant lower values compared with the controls regarding whole-image, foveal, and parafoveal deep VD. There were significant negative correlations between serum ferritin and deep (whole image and parafoveal) VD (r =  - 0.429, P = 0.026, and r =  - 0.452, P = 0.018, respectively). Choriocapillaris VDs (whole image and foveal) showed significant negative correlations with serum ferritin levels (r =  - 0.390, P = 0.044 and r =  - 0.401, P = 0.038, respectively) CONCLUSIONS: Macular microvascular changes were detected by OCTA examination in patients with TDT, mostly due to iron overload effect, as we selected patients on iron-chelating agent with the least harmful effect on the retina. The most affected layer is the DCP. Changes at the deep layer could be used as a sensitive biomarker for early macular perfusion changes in those patients.

TRIAL REGISTRATION

Study registration number is UMIN000042657, date of registration: 2020/12/04 (retrospectively registered).

Comparison of the Doppler Indices in the Ophthalmic Artery and Central Retinal Artery in Diabetic and Nondiabetic Individuals

Objective:

Diabetes can lead to diabetic retinopathy, which damages the retina due to blood flow remodeling of occular vessels. Early stages of diabetic retinopathy may not present with patient symptoms. Doppler indices, of the ophthalmic arteries, could help in determining the effect of diabetic vascular remodeling. This research was designed to compare the Doppler indices, in the ophthalmic artery and central retinal artery, in both diabetic and nondiabetic patients.

Materials and Methods:

This was a cross-sectional observational study of 72 total patients. Sonography was performed on the ophthalmic arteries of 36 diabetics and 36 nondiabetics, to compare Doppler indices. All patients were voluntarily consented to this research that was approved by the university’s Institutional Review Board (IRB). Doppler parameters recorded were peak systolic velocity, end dystopic velocity, resistive index, and pulsatility index, which were taken in both patient groups and compared.

Results:

A significant difference was noted in the ophthalmic artery peak systolic velocity, end-diastolic velocity, pulsatility index, and resistive index for diabetic and nondiabetic individuals, with a statistically significant set at .01.

Conclusions:

There was a significant difference between diabetic and nondiabetic ophthalmic Doppler indices in this cohort of patients. This cohort demonstrated vascular remodeling of the ophthalmic arteries, caused by diabetes; therefore, blood flow resistance was increased due to diabetes.

Reduced Superficial Capillary Density in Cerebral Infarction Is Inversely Correlated With the NIHSS Score

Purpose: The retina and the brain share similar neuronal and microvascular features, therein we aimed to assess the structural and microvascular changes in the macula and choriocapillaris (CC) in patients with cerebral infarction when compared with healthy controls using optical coherence tomography angiography (OCTA).

Methods: OCTA was used to image and measure the capillary density in the radial peripapillary capillaries (RPC), superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaris (CC), and mean area of the foveal avascular zone (FAZ) in all participants. Twenty-two cerebral infarction patients based on their magnetic resonance imaging (MRI) and 25 healthy controls were included in our study.

Results: Density of the RPC (P < 0.001), SCP (P = 0.001), DCP (P < 0.001) and CC (P < 0.001) were significantly reduced in cerebral infarction patients when compared with healthy controls, respectively. Retinal thickness measurements (P < 0.05) were significantly reduced in cerebral infarction patients when compared with healthy controls. The mean FAZ area was significantly larger (P = 0.012) in cerebral infarction patients when compared with healthy controls. National Institute of HealthStroke Scale (NIHSS) inversely correlated with SCP density in cerebral infarction patients (Rho = −0.409, P = 0.001). Receiver operating characteristics curve analysis showed that the blood flow of the choriocapillaris had the highest index [area under the receiver operatingcharacteristic (AUROC) = 0.964] to discriminate cerebral infarction patients from the healthy controls.

Conclusions: Our study suggests that cerebral microcirculation dysfunction which occurs in cerebral infarction is mirrored in the macula and choroidal microcirculation. OCTA has the potential to non-invasively characterize the macula and choroidal changes in cerebral infarction in vivo.

Exploratory study of non-invasive, high-resolution functional macular imaging in subjects with diabetic retinopathy

AIM

To evaluate a high-resolution functional imaging device that yields quantitative data regarding macular blood flow and capillary network features in eyes with diabetic retinopathy (DR).

METHODS

Prospective, cross-sectional comparative case-series in which blood flow velocities (BFVs) and non-invasive capillary perfusion maps (nCPMs) in macular vessels were measured in patients with DR and in healthy controls using the Retinal Functional Imager (RFI) device.

RESULTS

A total of 27 eyes of 21 subjects were studied [9 eyes nonproliferative diabetic retinopathy (NPDR), 9 eyes proliferative diabetic retinopathy (PDR) and 9 controls]. All diabetic patients were type 2. All patients with NPDR and 5 eyes with PDR also had diabetic macular edema (DME). The NPDR group included eyes with severe (n=3) and moderate NPDR (n=6), and were symptomatic. A significant decrease in venular BFVs was observed in the macular region of PDR eyes when compared to controls (2.61±0.6 mm/s and 2.92±0.72 mm/s in PDR and controls, respectively, P=0.019) as well as PDR eyes with DME compared to NPDR eyes (2.36±0.51 mm/s and 2.94±1.09 mm/s in PDR with DME and NPDR, respectively, P=0.01).

CONCLUSION

The RFI, a non-invasive imaging tool, provides high-resolution functional imaging of the retinal microvasculature and quantitative measurement of BFVs in visually impaired DR patients. The isolated diminish venular BFVs in PDR eyes compared to healthy eyes and PDR eyes with DME in comparison to NPDR eyes may indicate the possibility of more retinal vein compromise than suspected in advanced DR.

Foveal Avascular Zone Measurement Via Optical Coherence Tomography Angiography and its Relationship With the Visual Field in Eyes With Open-angle Glaucoma

PRECIS

The foveal avascular zone (FAZ) in optical coherence tomography angiography is significantly correlated with retinal inner layer thickness, Humphrey field analyzer (HFA) 10-2 sensitivity threshold, and mean deviation (MD) value in open-angle glaucoma patients.

PURPOSE

The purpose of this study was to measure the FAZ area using optical coherence tomography angiography and investigate its relationship with retinal inner layer thickness and visual field defects in eyes with open-angle glaucoma.

PARTICIPANTS AND METHODS

A total of 52 eyes with open-angle glaucoma from 52 patients. FAZ area was measured using optical coherence tomography angiography in angio-macula mode. Thicknesses of retinal nerve fiber layer (RNFL), ganglion cell layer plus inner plexiform layer (GCL+IPL), and ganglion cell complex (GCC) were determined using a 7 mm×7 mm macular (V) map via 3D-OCT. Correlations of FAZ area with sensitivity threshold measurements, foveal threshold (FT), and MD value in the HFA10-2 visual field were analyzed for each inner retinal layer.

RESULTS

FAZ area was 0.26±0.07 mm; overall mean thicknesses were 19.14±6.55 μm (RNFL), 57.34±5.93 µm (GCL+IPL), and 75.87±10.96 μm (GCC); mean FT was 35.23±3.15 dB, and sensitivity threshold was 20.81±7.22 dB in the HFA10-2 visual field. FAZ area was significantly correlated with the thickness of individual retinal layers in the entire field (RNFL, P<0.001; GCL+IPL, P<0.001; GCC, P<0.001), sensitivity threshold (P=0.01), FT (P<0.001), and MD value (P=0.011).

CONCLUSION

FAZ area was significantly negatively correlated with retinal inner layer thickness, sensitivity threshold, FT, and MD value in the HFA10-2 visual field.

Developing retinal biomarkers for the earliest stages of Alzheimer's disease: What we know, what we don't, and how to move forward

The last decade has seen a substantial increase in research focused on the identification, development, and validation of diagnostic and prognostic retinal biomarkers for Alzheimer's disease (AD). Sensitive retinal biomarkers may be advantageous because they are cost and time efficient, non-invasive, and present a minimal degree of patient risk and a high degree of accessibility. Much of the work in this area thus far has focused on distinguishing between symptomatic AD and/or mild cognitive impairment (MCI) and cognitively normal older adults. Minimal work has been done on the detection of preclinical AD, the earliest stage of AD pathogenesis characterized by the accumulation of cerebral amyloid absent clinical symptoms of MCI or dementia. The following review examines retinal structural changes, proteinopathies, and vascular alterations that have been proposed as potential AD biomarkers, with a focus on studies examining the earliest stages of disease pathogenesis. In addition, we present recommendations for future research to move beyond the discovery phase and toward validation of AD risk biomarkers that could potentially be used as a first step in a multistep screening process for AD risk detection.

The application of key feature extraction algorithm based on Gabor wavelet transformation in the diagnosis of lumbar intervertebral disc degenerative changes

OBJECTIVE

Based on the theoretical basis of Gabor wavelet transformation, the application effects of feature extraction algorithm in Magnetic Resonance Imaging (MRI) and the role of feature extraction algorithm in the diagnosis of lumbar vertebra degenerative diseases were explored.

METHOD

The structure of lumbar vertebra and degenerative changes were respectively introduced to clarify the onset mechanism and pathological changes of lumbar vertebra degenerative changes. Most importantly, the theoretical basis of Gabor wavelet transformation and the extraction effect of feature information in lumbar vertebra MRI images were introduced. The differentiation effects of feature information extraction algorithm on annulus fibrosus and nucleus pulposus were analyzed. In this study, the data of lumbar spine MRI was randomly selected from the Wenzhou Lumbar Spine Research Database as research objects. A total of 130 discs were successfully fitted, and 109 images were graded by a doctor after observation, which was compared with the results of the artificial diagnosis. Through the comparison with the results of observation and diagnosis by professional doctors, the accuracy of feature extraction algorithm based on Gabor wavelet transformation in the diagnosis of lumbar vertebra degenerative changes was analyzed.

RESULTS

1. Compared with the results of the manual diagnosis, the accuracy of the classification method was 88.3%. In addition, the specificity (SPE), accuracy (ACC), and sensitivity (SEN) of the classification method were respectively 89.5%, 92.4%, and 87.6%. 2. The mutual information method and the KLT algorithm were utilized for vertebral body tracking. The maximum mutual information method was more effective in the case of fewer image sequences; however, with the increase of image frames, the accumulation of errors would make the tracking effects of images get worse. Based on the KLT algorithm, the enhanced vertebral boundary information was selected; the soft tissues showed in the obtained images were smooth, the boundary information of vertebral body was enhanced, and the results were more accurate.

CONCLUSION

The feature extraction algorithm based on Gabor wavelet transformation could easily and quickly realize the localization of the lumbar intervertebral disc, and the accuracy of the results was ensured. In addition, from the aspect of vertebral body tracking, the tracking effects based on the KLT algorithm were better and faster than those based on the maximum mutual information method.

A Pilot Optical Coherence Tomography Angiography Study on Superficial and Deep Capillary Plexus Foveal Avascular Zone in Patients With Beta-Thalassemia Major

Purpose

To investigate foveal avascular zone (FAZ) changes in the superficial (SCP) and deep (DCP) capillary plexuses in beta-thalassemia major (BTM) patients, as shown in optical coherence tomography angiography.

Methods

Nonrandomized, comparative case series of 54 eyes of 27 BTM patients and 46 eyes of 23 healthy controls, utilizing an automated FAZ detection algorithm. Measurements included FAZ area and FAZ shape descriptors (convexity, circularity, and contour temperature). Results were compared between the two groups, and correlated to iron load and chelation therapy parameters.

Results

SCP and DCP FAZ area were not significantly different between the control and BTM groups (P = 0.778 and P = 0.408, respectively). The same was true regarding SCP FAZ convexity (P = 0.946), circularity (P = 0.838), and contour temperature (P = 0.907). In contrast, a statistically significant difference was detected between controls and BTM group regarding DCP FAZ convexity (P = 0.013), circularity (P = 0.010), and contour temperature (P = 0.014). Desferrioxamine dosage was strongly correlated to the DCP area (r = 0.650, P = 0.05) and liver magnetic resonance imaging/T2-star to DCP circularity (r = -0.492, P = 0.038). Correlations were also revealed between urine Fe excretion and DCP convexity (r = 0.531, P = 0.019), circularity (r = 0.661, P = 0.002), and contour temperature (r = -0.591, P = 0.008).

Conclusions

Retinal capillary plexuses and especially DCP seem to present unique morphologic changes in BTM patients, not in the FAZ area, but in specific shape descriptors, indicating minor but detectable FAZ changes. These changes correlate well with iron load and chelation therapy parameters. Their clinical importance and pathophysiologic implications remain to be elucidated through further studies.

[On classification of diabetic retinopathy]

The article analyses current state of the problem of diabetic retinopathy classifications based on the data from Russian and foreign literature on pathogenesis, clinical manifestations, results of multicenter studies on treatment and prognosis of the disease. Every existing classification was found to be limited in applications; attempts had been made to unify and complement them with the aim of achieving more complete and better-detailed description of the processes of diagnostics and determination of treatment algorithms. In conclusion, none of the existing classifications can be considered consistent in both clinical and practical aspects with respect to diabetic retinopathy.

Retinal Microvascular Abnormalities in Children with Type 1 Diabetes Mellitus Without Visual Impairment or Diabetic Retinopathy

Purpose

To study the characteristics and associated factors of retinal microvascular abnormalities in children with type 1 diabetes mellitus (T1DM) without visual impairment and diabetic retinopathy (DR).

Methods

Case-control hospital-based study including children with or without DM. Optical coherence tomography angiography (OCTA; CIRRUS HD-OCT model 5000) was used to scan 6 × 6 mm square area of posterior retina and optic disc. The indexes analyzed mainly included vascular length density (VD), perfusion density (PD), and foveal avascular zone area, perimeter, and morphology. Independent risk factors were analyzed by multifactor linear regression.

Results

A total of 47 children with T1DM and 44 healthy subjects were enrolled. Statistical analysis showed that VD within 1 to 3 mm (inner ring) of the macula in the case group was smaller than that in the control group (18.561 ± 1.151/mm: 19.161 ± 0.464/mm; P< 0.001), and mother's excessive weight gain during pregnancy was an independent factor (P = 0.004); VD within 3 to 6 mm (outer ring) of the macula in the case group was smaller than that in the control group (19.044 ± 0.847/mm; 19.404 ± 0.496/mm, P = 0.029), while serum creatinine level was revealed to be an independent factor (P = 0.009); PD within 3 to 6 mm of the macula in the case group was higher than that in the control group (0.456 ± 0.015: 0.442 ± 0.030) (P = 0.003), with no independent factor observed in regression analysis.

Conclusion

Retinal microvasculopathy had already occurred in the parafoveal area of diabetic children without visual impairment and DR; early screening and close follow-up were recommended for children with high-risk factors.

[Foveal avascular zone and OCT angiography. An overview of current knowledge]

BACKGROUND

The foveal avascular zone (FAZ) has often been analyzed under different aspects in the last decades, mainly by fluorescence angiography (FA); however, the novel technology of optical coherence tomography angiography (OCTA) enables a non-invasive examination, visualization and quantitative analysis of the FAZ, which has recently led to many new findings, especially in a multidisciplinary manner. This article provides an overview of the investigation of the FAZ using OCTA and the new findings that have been obtained using OCTA in recent years.

METHODS

This article is based on a comprehensive literature review.

RESULTS

In many studies a good reproducibility and repeatability of the FAZ measurements by OCTA could be proven, also by comparing different OCTA devices. In patients with ocular pathologies and systemic diseases, e. g. after retinal vein occlusion or retinal surgery and in patients with diabetes mellitus without diabetic retinopathy, differences to healthy control groups and correlations to visual function could be shown. Moreover, in patients with neurological diseases, such as Alzheimer's dementia, changes of the FAZ could be identified.

CONCLUSION

The OCTA is a non-invasive technology, which enables a reliable visualization and reproducible quantification of the FAZ. The size of the FAZ seems to be altered in different retinal and systemic diseases, which also may correlate with visual function; however, long-term studies evaluating the diagnostic value of these changes in the course of the disease are currently lacking.

Fully automated geometric feature analysis in optical coherence tomography angiography for objective classification of diabetic retinopathy

This study is to establish quantitative features of vascular geometry in optical coherence tomography angiography (OCTA) and validate them for the objective classification of diabetic retinopathy (DR). Six geometric features, including total vessel branching angle (VBA: θ), child branching angles (CBAs: α1 and α2), vessel branching coefficient (VBC), and children-to-parent vessel width ratios (VWR1 and VWR2), were automatically derived from each vessel branch in OCTA. Comparative analysis of heathy control, diabetes with no DR (NoDR), and non-proliferative DR (NPDR) was conducted. Our study reveals four quantitative OCTA features to produce robust DR detection and staging classification: (ANOVA, P<0.05), VBA, CBA1, VBC, and VWR1.

Foveal avascular zone area measurements using OCT angiography in patients with type 2 diabetes mellitus associated with essential hypertension

Objective. This study followed the variability in the foveal avascular zone (FAZ) area measured using optical coherence tomography angiography (OCTA) in patients with type 2 diabetes mellitus and high blood pressure. Material and Methods. This prospective, non-randomized, cohort study evaluated 46 eyes in 26 patients with high blood pressure associated with diabetic non-proliferative retinopathy (mild, medium, and severe forms) and diabetic proliferative retinopathy. Results. Our results showed early macular alterations (microaneurysms, leakage, neovascularizations, intraretinal microvascular abnormalities), a higher class of severity despite a relatively normal clinical aspect and higher values of FAZ associated with neovascularization undetected by SD-OCT (spectral domain-OCT). Conclusion. Measurement of the foveal avascular zone area using OCTA early detects macular alterations that precede classical retinography and SD-OCT determinations. Abbreviations: FAZ = foveal avascular zone; OCTA = optical coherence tomography angiography; IRMA = intraretinal microvascular abnormalities; SD-OCT = spectral domain-optical coherence tomography; OU = both eyes; PD = papillary diameter; ETDRS = early treatment diabetic retinopathy study; BP = blood pressure; OD = right eye.

Maximum value projection produces better en face OCT angiograms than mean value projection

Optical coherence tomography angiography (OCTA) images rely on en face data projections for both qualitative and quantitative interpretation. Both maximum value and mean value projections are commonly used, and many researchers consider them essentially interchangeable approaches. On the contrary, we find that maximum value projection achieves a consistently higher signal-to-noise ratio and higher image contrast across multiple vascular layers, in both healthy eyes and for each disease examined.

Investigating the Fractal Dimension of the Foveal Microvasculature in Relation to the Morphology of the Foveal Avascular Zone and to the Macular Circulation in Patients With Type 2 Diabetes Mellitus

In this study, we examined the relationship between the fractal dimension (FD), the morphology of the foveal avascular zone (FAZ) and the macular circulation in healthy controls and patients with type 2 diabetes mellitus (T2DM) with and with no diabetic retinopathy (DR). Cross-sectional data of 47 subjects were analyzed from a 5-year longitudinal study using a multimodal optical imaging approach. Healthy eyes from nondiabetic volunteers (n = 12) were selected as controls. Eyes from patients with T2DM were selected and divided into two groups: diabetic subjects with mild DR (MDR group, n = 15) and subjects with DM but without DR (DM group, n = 20). Our results demonstrated a higher FD in the healthy group (mean, 1.42 ± 0.03) than in the DM and MDR groups (1.39 ± 0.02 and 1.35 ± 0.03, respectively). Also, a bigger perimeter, area, and roundness of the FAZ were found in MDR eyes. A significant difference in area and perimeter (p ≤ 0.005) was observed for the MDR group supporting the enlargement of the FAZ due to diabetic complications in the eye. A moderate positive correlation (p = 0.014, R² = 43.8%) between the FD and blood flow rate (BFR) was only found in the healthy control group. The BFR calculations revealed the lowest values in the MDR group (0.98 ± 0.27 μl/s vs. 1.36 ± 0.86 μl/s and 1.36 ± 0.57 μl/sec in the MDR, DM, and healthy groups, respectively, p = 0.2). Our study suggests that the FD of the foveal vessel arborization could provide useful information to identify early morphological changes in the retina of patients with T2DM. Our results also indicate that the enlargement and asymmetry of the FAZ might be related to a lower BFR because of the DR onset and progression. Interestingly, due to the lack of FAZ symmetry observed in the DM and MDR eyes, it appears that the distribution of flow within the retinal vessels loses complexity as the vascular structures distributing the flow are not well described by fractal branching. Further research could determine how our approach may be used to aid the diagnosis of retinal neurodegeneration and vascular impairment at the early stage of DR.