Effect of anti-VEGF on retinal blood flow in diabetic mice using laser speckle flowgraphy

PURPOSE

To assess intra- (repeatability) and inter-observer (reproducibility) variability of laser speckle flowgraphy (LSFG) for retinal blood flow (RBF) measurement in 20 eyes of wild type (C57BL/6J) mice and effect of intravitreal Aflibercept on RBF in optic nerve head (ONH) region of 10 eyes of Ins2 (Akita) diabetic mice.

METHODS

'Mean blur rate (MBR)' was measured for all quadrants of tissue area (MT), vessel (MV) and total area (MA) of ONH region. Changes in MT were analysed at each timepoint. Repeatability was evaluated by measuring MBR variability without changing mouse head position, and reproducibility after resetting mouse head position by another operator. Coefficient of repeatability (CR) through Bland-Altman plot method coefficient of variation (COV) and Intraclass correlation coefficient (ICC) was calculated. Intravitreal Aflibercept (1 μg) was administered to Akita eyes and intraocular pressure (IOP) was measured using a tonometer at baseline, day 7, 14, 21 and 28 post-injection. Hurvich and Tsai's criterion was used.

RESULTS

Coefficient of repeatability values of repeatability and reproducibility for all quadrants were within limits of agreement. Reliability was excellent (ICC 0.98-0.99) and reproducibility was moderate to excellent (ICC 0.64-0.96). There was a non-significant IOP increase in all Akita eyes at Day 28 (p > 0.05), and significant increase in MT in all quadrants at Day 21 and superior, inferior and temporal quadrants at Day 28 (p < 0.05).

CONCLUSION

Laser speckle flowgraphy demonstrates excellent repeatability and moderate to excellent reproducibility in measuring RBF. Intravitreal Aflibercept injection results in a significant increase in MT up to 28 days post-injection without significant increase in IOP.

Pretreatment ocular blood flow and retinal oxygen metabolism in the acute uveitic phase is associated with final outcome in Vogt-Koyanagi-Harada disease

PURPOSE

To investigate the association between pretreatment blood flow velocity in the choroid and optic nerve head (ONH) and retinal oxygen metabolism in the acute uveitic phase and the development of 'sunset glow fundus' in Vogt-Koyanagi-Harada (VKH) disease.

METHODS

Retrospective analysis of 41 patients (82 eyes). Laser speckle flowgraphy and retinal oximetry measurements were performed at the presentation. The main outcome measure was the development of 'sunset glow fundus'.

RESULTS

Twenty patients (40 eyes) presented in the phase preceding anterior segment inflammation (early presentation), and 21 patients (42 eyes) presented with anterior segment inflammation (late presentation). In ONH, mean blur rate (MBR)-vessel, representing blood flow velocity in retinal vessels, was significantly lower in the late presentation group, while choroidal MBR was not significantly different. The late presentation group had significantly lower oxygen saturation in retinal venules, a higher arteriovenous oxygen saturation difference and a smaller calibre of retinal arterioles compared with the early presentation group. Eyes that subsequently developed 'sunset glow fundus' had significantly lower ONH MBR-vessels, lower oxygen saturation in retinal venules, a higher arteriovenous oxygen saturation difference and a smaller calibre of retinal arterioles compared with eyes without 'sunset glow fundus'. ONH MBR-vessel had a significant negative correlation with arteriovenous oxygen saturation difference and a significant positive correlation with calibre of retinal arterioles.

CONCLUSIONS

In the acute uveitic phase of VKH disease, the development of 'sunset glow fundus' is associated with pretreatment reduced retinal blood flow velocity, calibre of retinal arterioles and oxygen saturation in retinal venules, as well as an increased arteriovenous oxygen saturation difference.

Choroidal Circulatory and Vascular Morphological Changes in Acute Macular Neuroretinopathy After Infection With Severe Acute Respiratory Syndrome Coronavirus 2: A Case Report With Literature Review

BACKGROUND/AIM

The aim of this study was to analyze choroidal circulatory and structural changes using laser speckle flowgraphy (LSFG) and optical coherence tomography (OCT) in acute macular neuroretinopathy (AMN) after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively.

CASE REPORT

A 24-year-old woman complained of distorted vision after SARS-CoV-2 infection oculi uterque (OU) and referred to our hospital because of ellipsoid zones (EZ) disruption on OCT. Her best-corrected visual acuity (BCVA) was 1.2 OU. Color fundus photographs revealed dark red lesions in the macula, and scanning laser ophthalmoscopy infrared images showed hypointensity consistent with dark red lesions OU. We diagnosed the patient with AMN after SARS-CoV-2 infection, and posterior sub-Tenon injections of triamcinolone acetonide were performed OU. Five months after the initial visit, her BCVA was 1.2 OU, and EZ disruption improved. The rate of change in macular blood flow assessed by the mean blur rate on LSFG was 20.4% and 29.6% increase oculus dexter (OD) and oculus sinister (OS) 5 months after the initial visit, respectively. The central choroidal thickness showed 13.5% increase OD and 16.1% increase OS. The binarization technique demonstrated that the ratio of luminal areas in choroidal area increased by 12.6% OD and 14.2% OS, and stromal areas increased by 7.3% OD and 16.9% OS.

CONCLUSION

Before and after treatment for AMN, the luminal component may have increased with improvement of acute choroidal circulatory disturbance caused by SARS-CoV-2, and increased stromal components may be due to chronic inflammation and tissue remodeling of the stroma.

Effect of Ocular Dominance on Ocular Blood Flow Parameters

PURPOSE

In binocular vision, there is a dominant eye and a nondominant eye, a phenomenon termed ocular dominance. This study determined the differences and associations of the ocular blood flow parameters between dominant and nondominant eyes in healthy Japanese subjects.

METHODS

This cross-sectional study included 128 eyes of 64 subjects (13 male and 51 female) aged ≥ 20 years. The ocular blood flow parameters were assessed using laser speckle flowgraphy (LSFG), and software was used to calculate the mean blur rate (MBR), which reflects the blood flow velocity.

RESULTS

There were no significant differences in axial length (AL), spherical equivalent (SE), intraocular pressure (IOP), uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), or ocular blood flow parameters between the dominant and nondominant eyes. The ocular blood flow parameters of the dominant eye were significantly and positively correlated with those of the nondominant eye (all P < 0.001).

CONCLUSIONS

No significant differences in ocular blood flow parameters exist between the dominant and nondominant eyes in healthy subjects. The ocular blood flow parameters in the dominant eye are associated with those in the nondominant eye.

Parasympathetic Dominance Decreases the Choroidal Blood Flow Velocity Measured Using Laser Speckle Flowgraphy

BACKGROUND

This study aimed to examine the changes to choroidal blood flow velocity using laser speckle flowgraphy (LSFG) in healthy eyes after warm water immersion at 40°C.

METHODS

Data regarding the right eyes of 23 healthy volunteers were included. The mean blur rate (MBR) of the macula, which represents the choroidal blood flow velocity, was evaluated using LSFG. Intraocular pressure (IOP), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), ocular perfusion pressure (OPP), and MBR were assessed at baseline, immediately after immersion (0 minutes), and 10, 20, and 30 minutes later.

RESULTS

At 0 minutes, SBP, DBP, MBP, and OPP values were lower than those at baseline. The MBR significantly declined immediately after immersion to -6.0 ± 5.2%. However, there were no changes in these parameters after 10, 20, or 30 minutes. A significant positive correlation was observed between the MBR, SBP, DBP, MBP, and OPP values. In healthy individuals, the dominant parasympathetic activity induced by warm stimulation reduced the choroidal hemodynamic rate in the macula and decreased systemic circulatory dynamics, which normalized after 10 minutes.

CONCLUSIONS

These findings suggest that the dominant parasympathetic activity induced by warm water immersion at 40°C may lead to a reduction in the systemic circulation rate and choroidal blood flow rate in the macula. These findings may help prevent and treat various retinal choroidal diseases, in which sympathetic hyperactivity is involved in the pathogenesis of the disease.

Effects of Intravitreal Ranibizumab Injection on Peripheral Retinal Microcirculation and Cytokines in Branch Retinal Vein Occlusion with Macular Edema

Background and Objectives: To investigate peripheral blood flow in retinal vessels and vessel diameters after intravitreal ranibizumab injection (IRI) and the relationship between these parameters and cytokines in branch retinal vein occlusion (BRVO) with macular edema. Materials and Methods: We assessed relative flow volume (RFV) and the width of the main and branch retinal arteries and veins in the occluded and non-occluded regions before and after IRI in 37 patients with BRVO and macular edema. Measurements were made using laser speckle flowgraphy (LSFG). When performing IRI, we obtained samples of aqueous humor and analyzed them using the suspension array method to evaluate vascular endothelial growth factor (VEGF), placental growth factor (PlGF), platelet-derived growth factor (PDGF)-AA, soluble intercellular adhesion molecule (sICAM)-1, monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-6, IL-8, and interferon-inducible 10-kDa protein (IP-10). Results: In both retinal regions, before and after IRI, the RFV in the main artery and vein showed a significant correlation with the summed RFV in the respective branch vessels 1 and 2. In the occluded region, the RFV in the main vein was significantly negatively correlated with MCP-1, PDGF-AA, IL-6, and IL-8; the RFV in branch vein 1 was significantly negatively correlated with PlGF, MCP-1, IL-6, and IL-8; PDGF-AA was significantly negatively correlated with the width of the main and branch veins; and the RFVs of the main artery and vein decreased significantly from before to 1 month after IRI. Conclusions: Contrary to expectations, the study found that anti-VEGF therapy does not affect RFV in arteries and veins in patients with BRVO and macular edema. Furthermore, retinal blood flow is poor in patients with high MCP-1, IL-6, and IL-8. Finally, high PDGF-AA may result in smaller venous diameters and reduced retinal blood flow.

Changes in Choroidal Circulation Hemodynamics Measured Using Laser Speckle Flowgraphy after a Cold Pressor Test in Young Healthy Participants

Using laser speckle flowgraphy (LSFG), we investigated the time course of changes in choroidal circulation hemodynamics after a cold pressor test in healthy eyes. This prospective study included the right eye of 19 young healthy participants. The macular mean blur rate (MBR) was measured with LSFG. The MBR, intraocular pressure (IOP), systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), mean blood pressure (MBP), and ocular perfusion pressure (OPP) were evaluated at baseline; immediately after the test and 10, 20, and 30 min later. Immediately after the test (0 min), SBP, DBP, MBP, and OPP were significantly elevated compared with those at baseline. The macular MBR significantly increased by +10.3 ± 7.1% immediately after the test. However, there was no change after 10, 20, and 30 min in the above parameter. A significant positive correlation of the macular MBR with the SBP, MBP, and OPP was observed. In young healthy individuals, increased sympathetic activity induced by a cold pressor test increases choroidal hemodynamics in the macula along with an increase in systemic circulatory dynamics, which normalizes after 10 min. Therefore, LSFG may provide a novel approach for assessing sympathetic activity and intrinsic vascular responsiveness in the eye.

Ocular blood flow evaluation by laser speckle flowgraphy in pediatric patients with anisometropia

Purpose

To determine the differences and reproducibility of blood flow among hyperopic anisometropic, fellow, and control eyes.

Methods

We retrospectively studied 38 eyes of 19 patients with hyperopic anisometropia (8.2 ± 3.0 years of age) and 13 eyes of eight control patients (6.8 ± 1.9 years). We measured the optic nerve head (ONH) and choroidal circulation using laser speckle flowgraphy (LSFG) and analyzed the choroidal mean blur rate (MBR-choroid), MBR-A (mean of all values in ONH), MBR-V (vessel mean), MBR-T (tissue mean), and sample size (sample), which are thought to reflect the ONH area ratio, area ratio of the blood stream (ARBS). We then assessed the coefficient of variation (COV) and intraclass correlation coefficient (ICC) and compared the differences among amblyopic, fellow, and control eyes in MBR, sample, and ARBS.

Results

The ONH, MBR-A, MBR-T, and ARBS of amblyopic eyes were significantly higher than those of fellow eyes (P < 0.01, P < 0.05, and P < 0.05, respectively), and control eyes (MBR-A and ARBS, P < 0.05, for both comparisons). The sample-T (size of tissue component) in amblyopic eyes was significantly smaller than that in fellow and control eyes (P < 0.05). Blood flow in the choroid did not differ significantly between the eyes. The COVs of the MBR, sample, and ARBS were all ≤10%. All ICCs were ≥0.7. The COVs of pulse waveform parameter fluctuation, blowout score (BOS), blowout time (BOT), and resistivity index (RI) in the ONH and choroid were ≤10%.

Conclusion

The MBR value of the LSFG in children exhibited reproducibility. Thus, this method can be used in clinical studies. The MBR values of the ONH in amblyopic eyes were significantly high. It has been suggested that measuring ONH blood flow using LSFG could detect the anisometropic amblyopic eyes.

Relationship Between Retinal Microcirculation and Renal Function in Patients with Diabetes and Chronic Kidney Disease by Laser Speckle Flowgraphy

This study investigated the effect of renal dysfunction categorized by the stage of chronic kidney disease (CKD) on the retinal microcirculation assessed by laser speckle flowgraphy (LSFG) and retinal artery caliber measured by adaptive optics imaging in diabetic patients particularly the early stage of retinopathy and nephropathy. We divided the patients with diabetes into three groups based on the CKD stage (non-CKD (n = 54); CKD stage 1 + 2 (n = 20); CKD stage 3 (n = 41)). The mean blur rate (MBR) of the stage 3 CKD group was significantly lower than that of the no-CKD group (p < 0.015). The total retinal flow index (TRFI) in the stage 3 CKD group was significantly lower than that of the no-CKD group (p < 0.002). Multiple regression analysis demonstrated that CKD stage was independently associated with MBR (β = -0.257, p = 0.031) and TRFI (β = -0.316, p = 0.015). No significant differences were observed in external diameter, lumen diameter, wall thickness, and wall to lumen ratio among the groups. These results indicated that the ONH MBR and TRFI as assessed by LSFG decreases in diabetic patients with stage 3 CKD, but the arterial diameter measured by adaptive optics imaging does not change, suggesting that impaired renal function may be associated with decreased retinal blood flow in early-stage diabetic retinopathy.

Decrease in Ocular Blood Flow Thirty Minutes After Intravitreal Injections of Brolucizumab and Aflibercept for Neovascular Age-Related Macular Degeneration

Purpose

Intravitreal injections of anti-vascular endothelial growth factor (VEGF) agents such as brolucizumab and aflibercept are used widely to treat neovascular age-related macular degeneration (nAMD); however; they may theoretically affect the ocular blood flow. We investigated the short-term changes in the ocular blood flow between eyes with nAMD treated with intravitreal brolucizumab injections (IVBr) and intravitreal aflibercept injections (IVA).

Methods

This study included 21 eyes of 21 Japanese patients with nAMD treated with either IVBr or IVA at Kurume University Hospital from April 2021 through June 2022. The rates of ocular blood flow at the optic nerve head (ONH mean blur rate [MBR]-vessel) and at the choroid (CHOR MBR) were analyzed before and 30 minutes after injections using laser speckle flowgraphy.

Results

In the IVBr-treated group, the ONH MBR-vessel and CHOR MBR rates decreased significantly by 10.6% and 16.9% from baseline to 30 minutes after IVBr, respectively. In the IVA-treated group, ONH MBR-vessel and CHOR MBR rates decreased significantly by 9.4% and 6.1% from baseline to 30 minutes after IVA, respectively. There was no significant difference in the rates of decrease in the ONH MBR-vessel or CHOR MBR between the IVBr-treated and IVA-treated groups.

Conclusion

Intravitreal injections of brolucizumab and aflibercept in eyes with nAMD cause significant decreases in ocular blood flow at the ONH and the choroid 30 minutes after injection. The rate of decrease in ocular blood flow was not significant between the eyes treated with brolucizumab and aflibercept. However, 3 of 10 eyes treated with brolucizumab but none of 11 eyes treated with aflibercept had more than a 30% decrease in the ocular blood flow at the choroid 30 minutes after injection.

Aldosterone as a Possible Contributor to Eye Diseases

Aldosterone, an effector molecule of the renin-angiotensin-aldosterone system (RAAS), has been receiving more attention in the field of ophthalmology because of its possible role in the pathogenesis of various eye diseases or abnormalities; it may even become a target for their treatment. Primary aldosteronism, a typical model of a systemic aldosterone excess, may cause vision loss due to various ocular diseases, such as retinal vein occlusion, central serous chorioretinopathy, and, possibly glaucoma. RAAS components are present in various parts and types of cells present in the eye. Investigations of the local RAAS in various animal models of diabetic macular edema, retinal vein occlusion, retinopathy of prematurity, central serous chorioretinopathy, and glaucoma have found evidence that aldosterone or mineralocorticoid receptors may exacerbate the pathology of these disorders. Further studies are needed to elucidate whether the modulation of aldosterone or mineralocorticoid receptors is an effective treatment for preventing vision loss in patients with eye diseases.

Correlation Between Laser Speckle Flowgraphy and OCT-Derived Retinal and Choroidal Metrics in Healthy Human Eye

Purpose

To investigate the correlation between laser speckle flowgraphy (LSFG) signals and the quantitative metrics derived from optical coherence tomography (OCT) in normal eyes.

Methods

LSFG, OCT, and OCT angiography (OCTA) imaging were performed on normal participants using a custom-designed LSFG system and a commercial swept-source OCT system. Mean (PWM) and amplitude (PWA) of the LSFG pulse waveform were selected to quantify the LSFG signals. Retinal and choroidal maps were obtained using the standard 6 × 6 mm OCT and OCTA scans. Structural and vascular metrics maps, including thickness, vessel area density, vessel skeleton density, and vessel diameter index of the retina, and choroidal thickness (CT), choroidal vessel volume (CVV) and choroidal vessel index (CVI), were employed to quantify the retinal and choroidal properties. Correlation analysis was then performed between the LSFG, retinal, and choroidal metrics maps.

Results

Twelve healthy participants aged 23 to 36 years were enrolled in this study. The spatial distribution of the PWM and PWA values was highly correlated with that of the CT and CVV metrics. On average, Spearman correlation coefficients (ρ) were 0.80 and 0.78 (all P < 0.001) for the correlations between PWM and CT and CVV, respectively, and were 0.61 and 0.63 (all P < 0.05) for the correlations between PWA and CT and CVV, respectively. In comparison, both PWM and PWA were generally weak or not correlated with all the retinal metrics and CVI.

Conclusions

LSFG signals were positively correlated with the choroidal thickness and vessel volume, suggesting choroidal blood flows dominate the LSFG signals at the area absent of large retinal vessels.

Translational Relevance

This study illustrates the dominant source of the LSFG signals in the eye.

Compromised blood flow in the optic nerve head after systemic administration of 2 aldosterone in rats: A possible rat model of retinal ganglion cell loss

PURPOSE

To investigate the optic nerve head (ONH) blood flow, retinal vessel diameters, and retinal ganglion cell (RGC) loss after systemic administration of aldosterone in rats.

METHODS

Aldosterone (80 μg/kg/day) or vehicle was administered using an osmotic minipump in Brown Norway rats. The mean blur rate in the vessel (MV) and tissue (MT) regions and retinal vessel diameters in the ONH were measured by laser speckle flowgraphy before and 1, 2, and 4 weeks after administration of aldosterone or vehicle. Intraocular pressure (IOP), blood pressure, and heart rate were recorded. The retrogradely labeled RGCs were counted in the retinal flatmounts prepared 5 weeks after treatment.

RESULTS

The MV and MT in the aldosterone group significantly decreased at 2 and 4 weeks (MV: 2 weeks, P = 0.001, 4 weeks, P < 0.001; MT: 2 weeks, P = 0.02, 4 weeks, P = 0.03). The artery and vein diameters significantly decreased at 1, 2, and 4 weeks in the aldosterone group (all P < 0.001). The MV, MT, and vessel diameters remained unchanged in the vehicle group. Other parameters did not change over time in either group. RGC counts were significantly lower in the aldosterone group than in the vehicle group (P < 0.001).

CONCLUSIONS

ONH blood flow decreased following retinal vessel constriction without changes in IOP or blood pressure in a possible rat model of RGC loss by systemic administration of aldosterone.

Measuring optic nerve head perfusion to monitor glaucoma: a study on structure-function relationships using laser speckle flowgraphy

PURPOSE

We aimed to describe the global and localized correlations among visual field (VF) sensitivity, optic nerve head (ONH) perfusion measured by laser speckle flowgraphy (LSFG) and neural structure measured by optical coherence tomography (OCT) in open-angle glaucoma (OAG) and to compare the floor effect for LSFG and OCT.

METHODS

Cross-sectional, multicenter study including one eye each from fifty OAG patients (mean age 69.3 years; average VF mean deviation, MD, -8.5 dB, range -25.17 to 0.85 dB) and fifty-one controls. Patients underwent SITA standard 24-2 automated perimetry and measurement of ONH perfusion, peripapillary retinal nerve fibre layer thickness (RNFLT) and macular ganglion cell-inner plexiform layer thickness (GCIPLT). We tested the presence of a significant change (breakpoint) in the correlation slope with VF sensitivity to assess floor effect.

RESULTS

The correlation between the LSFG parameter Mean All (MA) of the global disc area and MD (r = 0.56, p < 0.001) did not show a breakpoint, in contrast to the correlations between MD and OCT global parameters, which showed breakpoints at -8.53 and -4.05 dB for RNFLT and GCIPLT, respectively. Global and localized correlations with VF sensitivity were stronger for LSFG compared to OCT. In particular, LSFG outperformed OCT in the correlation with the central VF sector (r = 0.50, p < 0.001 and r = 0.06, p = 0.67 for MA and RNFLT, respectively).

CONCLUSION

The global and sectoral correlations with VF sensitivity and the favourable floor effect compared to OCT indicate LSFG as a promising tool to monitor progression particularly in late-stage glaucoma. Further longitudinal studies are warranted.

Removing dynamic distortions from laser speckle flowgraphy using Eigen-decomposition and spatial filtering

Laser speckle flowgraphy (LSFG) has been widely used in the investigation of blood flows in ophthalmology. However, the dynamic changes of the ocular optics can impose artificial contrasts to the LSFG, corrupting the detection of both retinal vasculature and blood pulsation at the posterior segment of the human eye. In this study, we propose to use Eigen-decomposition method to separate the spatially and temporally varying speckle patterns from the static tissues. Spatial filtering is further applied to remove the distortion-correlated modulation of the speckle patterns. We experimentally show that with the proposed method, the integrity of blood vessels is significantly improved and the distortions in pulse waveforms can be well corrected.

Effect of immunosuppressive therapy on ocular blood flow in initial-onset acute uveitis associated with Vogt-Koyanagi-Harada disease

PURPOSE

To investigate the effect of immunosuppressive therapy on blood flow and waveform parameters in the choroid and optic nerve head (ONH) in patients with initial-onset acute uveitis associated with Vogt-Koyanagi-Harada (VKH) disease.

METHODS

In this prospective study, 18 patients (36 eyes) were studied. Laser speckle flowgraphy was performed at baseline and at 4 weeks, 8 weeks and 12 weeks after treatment. We analysed longitudinal changes in mean blur rate (MBR), blow-out time, blow-out score (BOS), acceleration time index (ATI), flow acceleration index (FAI), resistivity index (RI) and blood flow fluctuation.

RESULTS

After immunosuppressive therapy, MBR, representing blood flow velocity, in the choroid and ONH significantly increased at each post-treatment time point compared to baseline values. Among the analysed pulse waveform parameters, BOS significantly increased, while RI and fluctuation significantly decreased. Increased BOS and decreased RI indicate decreased vascular resistance following treatment. There was a strong negative correlation between BOS and RI. Additionally, FAI increased in the choroid and ATI increased in ONH.

CONCLUSIONS

Immunosuppressive therapy in the acute uveitic phase of VKH disease improved inflammation-related impairment in choroidal and ONH blood flow.

Differential pial and penetrating arterial responses examined by optogenetic activation of astrocytes and neurons

A variety of brain cells participates in neurovascular coupling by transmitting and modulating vasoactive signals. The present study aimed to probe cell type-dependent cerebrovascular (i.e., pial and penetrating arterial) responses with optogenetics in the cortex of anesthetized mice. Two lines of the transgenic mice expressing a step function type of light-gated cation channel (channelrhodopsine-2; ChR2) in either cortical neurons (muscarinic acetylcholine receptors) or astrocytes (Mlc1-positive) were used in the experiments. Photo-activation of ChR2-expressing astrocytes resulted in a widespread increase in cerebral blood flow (CBF), extending to the nonstimulated periphery. In contrast, photo-activation of ChR2-expressing neurons led to a relatively localized increase in CBF. The differences in the spatial extent of the CBF responses are potentially explained by differences in the involvement of the vascular compartments. In vivo imaging of the cerebrovascular responses revealed that ChR2-expressing astrocyte activation led to the dilation of both pial and penetrating arteries, whereas ChR2-expressing neuron activation predominantly caused dilation of the penetrating arterioles. Pharmacological studies showed that cell type-specific signaling mechanisms participate in the optogenetically induced cerebrovascular responses. In conclusion, pial and penetrating arterial vasodilation were differentially evoked by ChR2-expressing astrocytes and neurons.

Clinical Application of Laser Speckle Flowgraphy to Assess Changes in Blood Flow to the Foot After a Lumbar Sympathetic Ganglion Block: A Case Report

Background

The lumbar sympathetic ganglion block (LSGB) has been used as a diagnostic and therapeutic procedure for treating pain conditions such as neuropathic and ischemia-related pain, affecting the lower extremities. In general, an increase in skin temperature is useful in confirming the effectiveness of the sympathetic nerve block in clinical settings. However, the assessment of skin temperature in patients with peripheral arterial disease (PAD) occasionally provides false negatives.

Case Presentation

A novel technology, laser speckle flowgraphy (LSFG) enables noninvasive quantitative and qualitative blood flow assessments. LSFG is a novel neuro-monitor for quantitative blood flow detection in the optic nerve head during cardiac surgery. Herein, we report on measuring foot blood flow using LSFG before and after LSGB in a PAD patient. This research aimed to determine whether LSFG could detect any improvement in the dynamics of foot blood flow after an LSGB in a situation where changes in skin temperature alone could not determine the procedure's outcome.

Conclusion

LSFG can be used to assess blood flow changes in a foot with PAD, following a LSGB.

The influence of hemorrhagic shock on ocular microcirculation by obtained by laser speckle flowgraphy in a white rabbit model

PURPOSE

To clarify the continuous changes in the retinal vessels' and choroid's microcirculation during hemorrhagic shock and resuscitation in a rabbit model.

METHODS

Hemorrhagic shock by the removal of blood (30 mL) and resuscitation by a blood-return technique was induced in anesthetized male New Zealand White rabbits (n = 10). We evaluated the retinal vessel blood flow (relative flow volume: RFV) and choroidal blood flow (mean blur rate in the choroid area: MBR-CH) by laser speckle flowgraphy (LSFG), with simultaneous measurements of systemic hemodynamics and laboratory parameters.

RESULTS

RFV and MBR-CH showed significant decreases immediately after the initiation of blood removal and recovered by blood return. The lactate concentration tended to increase from baseline by the blood-removal operation, and it was significantly higher at the end of observation period. The %RFV and %MBR-CH each showed a significant positive correlation with mean arterial blood pressure, cardiac output, carotid blood flow, and central venous pressure. %RFV showed a significant positive correlation with %central venous oxygen saturation and negatively correlated with %lactate. The %hemoglobin did not show a significant correlation with %RFV or %MBR-CH.

CONCLUSION

This rabbit hemorrhagic shock model confirmed that ocular microcirculation measurements by LSFG feasibly reflect variations in systemic hemodynamics during hemorrhagic shock and recovery.

Ocular and Systemic Factors Affecting Laser Speckle Flowgraphy Measurements in the Optic Nerve Head

Purpose

To investigate the ocular and systemic factors related to glaucoma and to be adjusted for interindividual comparison of ocular blood flow measurement results by laser speckle flowgraphy (LSFG) obtained from the optic nerve head (ONH) in normal Japanese individuals.

Methods

A multicenter, prospective cross-sectional study was conducted. The ONH tissue-area and vessel-area mean blur rate (MT and MV) were evaluated using LSFG and ONH structural parameters using planimetric methods. Multivariate linear mixed-effects modeled regression analysis was used to identify the contributing factors to the MT and MV. The explanatory variables were age; gender; smoking history; body mass index; mean arterial pressure (MAP); heart rate; intraocular pressure; axial length (AL); disc, rim, cup, and β-peripapillary atrophy (β-PPA) areas; and central retinal artery and vein equivalents.

Results

In total, 195 eyes of 126 healthy individuals with an average age of 48.1 years were included. Multivariate analysis showed that MAP and disc area had a negative (P < 0.001) correlation, whereas β-PPA area had a positive correlation with MT (P = 0.010). Age and AL had a negative correlation (P = 0.001 and P = 0.011, respectively), whereas cup area had a positive correlation (P = 0.012) with MV.

Conclusions

Interindividual comparison of MT or MV must be adjusted for both systemic factors (blood pressure or age) and local ocular factors (AL and disc, cup, or β-PPA area).

Translational Relevance

Our results provided reference data on the LSFG measurement and are important in comparing ocular blood flow between individuals using LSFG.

Retinal Microcirculation and Cytokines as Predictors for Recurrence of Macular Edema after Intravitreal Ranibizumab Injection in Branch Retinal Vein Occlusion

Purpose: To investigate the relationship between retinal blood flow, presence or absence of recurrence of macular edema, and levels of cytokines, after intravitreal ranibizumab injection (IRI) in patients with branch retinal vein occlusion (BRVO). Methods: In 47 patients with BRVO and macular edema, we used laser speckle flowgraphy (LSFG) to measure the relative flow volume (RFV) of the retinal arteries and veins passing through the optic disc in the occluded and non-occluded regions of the retina before and after IRI. Aqueous humor samples were obtained at the time of IRI. Levels of vascular endothelial growth factor (VEGF), soluble VEGF receptor (sVEGFR)-1, sVEGFR-2, placental growth factor (PlGF), platelet-derived growth factor (PDGF)-AA, soluble intercellular adhesion molecule (sICAM)-1, monocyte chemoattractant protein 1 (MCP-1), interleukin (IL)-6, IL-8, IL-12 (p70), IL-13 and interferon-inducible 10-kDa protein (IP-10) were measured by the suspension array method. Patients were categorized into two groups on the basis of whether or not macular edema recurred at 2 months after IRI: the nonrecurrent group, n = 24; and the recurrent group, n = 23. Results: In the veins of the occluded region, RFV showed a significant difference between baseline and 1 month after IRI (p < 0.001) in the recurrent group and the percent change of RFV showed a significant difference between the recurrent and nonrecurrent groups (p = 0.005). Furthermore, we found a significant negative correlation between RFV in the veins of the occluded region and aqueous levels of MCP-1, IL-8 and IP-10 at baseline (p = 0.029, p = 0.035, and p = 0.039, respectively). In the recurrent group, the arteries and veins of the non-occluded and occluded regions showed no significant association between RFV and the aqueous levels of any factors. Conclusions: These findings suggested that a decrease in RFV in the veins of the occluded region might be associated with the recurrence of macular edema and that the recurrence might depend on the change in RFV in the veins of the occluded region rather than the levels of cytokines.

Retinal Microvascular Resistance Estimated from Waveform Analysis Is Significantly Higher With a Threshold Value in Central Retinal Vein Occlusion

Purpose

Evaluation of blood flow is useful for understanding the severity of central retinal vein occlusion (CRVO). Actual blood flow may be determined by the resistivity of the retinal vein in CRVO. We have previously evaluated mean blur rate (MBR) to reflect total retinal blood flow velocity in CRVO cases using laser speckle flowgraphy (LSFG). This study evaluated retinal total vascular resistance in CRVO cases using the new index of total capillary resistance (TCR) from LSFG.

Methods

We measured the TCR of 68 CRVO patients who visited Nagasaki University Hospital between 2009 and 2016 and 42 age-matched controls without systemic disease. We compared TCRs among control eyes, CRVO fellow eyes, and CRVO affected eyes. A CRVO threshold value was then obtained from the receiver operating characteristic curve.

Results

MBR was significantly lower for CRVO affected eyes (20.3 ± 8.2) than for control eyes (37.5 ± 8.4; P < 0.01) and CRVO fellow eyes (36.4 ± 10.0; P < 0.01, Dunn's test). TCR was significantly higher for CRVO affected eyes (1.20 ± 0.55) than for control eyes (0.68 ± 0.2; P < 0.01) and CRVO fellow eyes (0.81 ± 0.28; P < 0.01, Dunn's test). The threshold for the presence of CRVO was 0.93 and area under the curve was 0.84.

Conclusions

By measuring TCR in addition to MBR, more detailed information regarding CRVO pathology can be obtained.

Translational Relevance

Comparison of values before and after treatment may be useful for evaluating the effects of treatment.

Laser speckle flowgraphy in juxtapapillary retinal capillary hemangioblastoma: a case report on natural course and therapeutic effect

Juxtapapillary retinal capillary hemangioblastoma (JRCH), a benign intraocular vascular tumor, is usually progressive and may lead to severe vision loss due to various complications. We herein present a case of JRCH observed with laser speckle flowgraphy (LSFG) before and after laser photocoagulation (LPC). A 21-year-old Japanese woman underwent LSFG evaluations. Right eye showed an orange-colored tumor consistent with JRCH on the papillomacular bundle, where LSFG showed a mild warm-color blood flow signal. Eight months after the first examination, JRCH in the right eye increased redness with vasodilatation, and the size enlarged, where LSFG showed a stronger warm-color blood flow signal. She underwent direct yellow laser ablation for the JRCH lesion. One week after LPC, JRCH became paler and LSFG eventually depicted a weakened blood flow signal at the same site. In conclusion, non-invasive and reproducible LSFG is a useful tool for assessing not only JRCH activity but also therapeutic effect.

The optic nerve head vasoreactive response to systemic hyperoxia and visual field defect progression in open-angle glaucoma, a pilot study

PURPOSE

To investigate the effect of optic nerve head (ONH) tissue vasoreactivity on glaucoma visual field defect progression.

METHODS

This prospective, longitudinal study comprised 28 eyes of 16 patients with open-angle glaucoma. Baseline data were obtained from oxygen inhalation testing, including laser speckle flowgraphy measurements of tissue-area mean blur rate (MT), which represents ONH tissue blood flow, and the mean percentage change in MT (MT-change). Follow-up data were collected for at least 2 years, including at least 5 reliable visual field tests. The average total deviation (TD) was calculated in each sector of the Garway-Heath map; in this study, superior, central and inferior TD corresponded to inferior, temporal and superior MT or MT-change, respectively. MT and MT-change in three sectors per eye were included as explanatory variables in a multivariable linear mixed-effects model, with TD slope set as the response variable.

RESULTS

At baseline, lower MT and higher diastolic blood pressure were associated with lower MT-change (p < 0.05). Additionally, MT-change significantly contributed to TD slope in the corresponding sectors (β = 0.41, p = 0.01).

CONCLUSIONS

Weaker ONH tissue vasoreactivity to systemic hyperoxia, assessed with laser speckle flowgraphy, was associated with lower baseline ONH tissue blood flow, higher diastolic blood pressure and rapid visual field defect progression. Laser speckle flowgraphy variables during oxygen provocation testing may represent potentially useful predictive biomarkers of glaucoma progression.

Optic Nerve Head Blood Flow Analysis in Patients with Optic Disc Drusen Using Laser Speckle Flowgraphy

Visual field defects are common in patients with optic disc drusen (ODD). Our aim was to examine whether reduced optic nerve head (ONH) microcirculation is related to visual field defects in ODD patients. Vascular and tissue area mean blur rate (MBR_V and MBR_T), measured using laser speckle flowgraphy (LSFG), was significantly lower in the 32 included ODD eyes when compared with 40 healthy eyes (p <.05). There was a moderate correlation between the difference in MBR_T and the perimetric mean defect (R² = 0.53) in ODD patients. These findings demonstrate the utility of LSFG in examining ONH blood flow in ODD patients.

Time Course in Ocular Blood Flow and Pulse Waveform in a Case of Ocular Ischemic Syndrome with Intraocular Pressure Fluctuation

We report on a 70-year-old Japanese man with complaints of worsening left visual acuity who was diagnosed with ocular ischemic syndrome (OIS) associated with internal carotid artery (ICA) stenosis. A gonioscopy examination showed rubeosis iridis and elevated intraocular pressure (IOP) in the left eye (50 mmHg) at the baseline visit. The optic nerve head (ONH) and choroidal blood flow measured by laser speckle flowgraphy (LSFG) was impaired in the left eye compared with that in the right eye. Additionally, the blowout score (BOS), which indicates the variation of the mean blur rate (MBR) during systolic and diastolic periods, was decreased in the left eye. After treatment with an injection of bevacizumab and administration of Rho-associated kinase-inhibitor ripasudil eye drops, both ocular blood flow and BOS in each vascular bed gradually increased along with IOP reduction. The visual acuity also improved. The current case demonstrated increased blood flow and decreased fluctuation of blood flow in the ONH and choroid before and after the treatment in OIS with rubeosis iridis. The LSFG technique is useful to non-invasively assess the ocular circulation and pulse waveform in OIS.

Assessment of Choroidal Neovascularization Perfusion: A Pilot Study With Laser Speckle Flowgraphy

Purpose

The purpose of this study was to quantify perfusion in the area of choroidal neovascularization (CNV) using laser speckle flowgraphy (LSFG) before and after intravitreal anti-vascular endothelial growth factor (VEGF) injection.

Methods

Retrospective case series. Fifteen eyes of 15 patients with treatment-naïve CNV due to age-related macular degeneration (AMD) and with available LSFG images were included. The main outcome was the mean blur rate (MBR) quantified as a measure of perfusion within the CNV area observed on indocyanine green angiography. Twelve patients had available longitudinal data until one month after the injection, used to evaluate changes in perfusion, central macular thickness (CMT), visual acuity, and ocular perfusion pressure. Reproducibility of LSFG measurements was investigated at each time point from two images taken within five minutes.

Results

Intraclass correlation coefficients for LSFG measurements were higher than 0.8 indicating excellent reproducibility. There was a significant decrease in perfusion after one week (-26.4 ± 14.4%; P = 0.027), whereas, after one month, perfusion was no longer significantly different from baseline (P = 0.121). CMT showed a progressive decrease over the follow-up period. Changes in perfusion were strongly correlated with changes in CMT after one week, but not thereafter.

Conclusions

This pilot study suggests a method to select a region in the CNV area to quantify perfusion using LSFG. MBR could represent a parameter possibly related to regrowth of the CNV after anti-VEGF treatment. Large-scale studies are needed to assess the usefulness of LSFG in defining re-treatment criteria for neovascular AMD.

Translational Relevance

LSFG technology to quantify perfusion could provide useful biomarkers for therapeutic management of CNV.

Correlation between laser speckle flowgraphy and optical coherence tomography angiography measurements in normal and glaucomatous eyes

Purpose

To investigate the relationship between laser speckle flowgraphy (LSFG) and optical coherence tomography angiography (OCTA) measurements of the peripapillary retina and optic nerve head (ONH) in normal eyes and eyes with primary open-angle glaucoma (POAG).

Patients and methods

One eye from each of 46 normal subjects and mild and moderate/advanced POAG patients were included. ONH blood flow acquired by LSFG, circumpapillary vessel density (cpVD, a 250 μm-wide elliptical annulus around the optic disc), and intra-papillary vessel density (ipVD, a 1.5×1.5 mm scan field) acquired by OCTA were measured. Their values were compared among normal controls and patients at each stage of glaucoma using one-way ANOVA, and the correlation between measurements obtained by the two methods was examined by univariate regression analysis.

Results

ONH tissue blood flow, tissue mean blur rate (MBR-T), and cpVD in the outer layer of the retina significantly decreased with the progression of glaucoma stage, although the latter showed no significant difference between normal subjects and mild-stage glaucoma patients. MBR-T was significantly correlated with cpVD, but not with ipVD, in the retinal outer layer.

Conclusion

A correlation was found only between MBR-T and cpVD in the retinal outer layer. A difference in MBR-T, but not in cpVD, was detected between normal controls and mild glaucoma patients.

Short-term effect on the ocular circulation induced by unilateral intravitreal injection of aflibercept in age-related maculopathy

Purpose

Intravitreal injection of anti‐vascular endothelial growth factor (anti‐VEGF) is the standard treatment for neovascular age‐related macular degeneration (AMD). As VEGF is a physiological key player for regulating retinal vascular tone, questions have been raised whether the application of anti‐VEGF could induce alterations in ocular perfusion.

Methods

The study included 20 eyes from 20 Caucasian patients with unilateral neovascular AMD and 20 fellow eyes. All eyes were treated with standard intravitreal injection of aflibercept (IVA). Measurements of blood flow at the optic nerve head (ONH) and the choroid were performed with laser speckle flowgraphy (LSFG). The intraocular pressure (IOP), systolic and diastolic blood pressure, heart rate, mean arterial pressure (MAP) and ocular perfusion pressure (OPP) were analysed. Measurements were performed at baseline and repeated immediately after the injection and 30 and 45 min later.

Results

Mean time between injection of aflibercept and first follow‐up was 8:56 ± 4:25 min. The injection led to significant rise in IOP. In the injected eyes, mean blur rate (MBR, i.e. a relative measure of perfusion and the main outcome parameter of LSFG) within the major vessels of the ONH as well as at the entire ONH region decreased significantly (p < 0.001). No change in MBR was observed in the fellow eye. Choroidal blood flow was maintained stable in both eyes.

Conclusion

Intravitreal injection of aflibercept (IVA) led to a short‐term reduction in perfusion only in the treated eye. This was independent from IOP, indicating a direct pharmacological effect. No changes in choroidal perfusion were observed during the first 45 min after the injection.

Non-invasive measurement techniques for quantitative assessment of optic nerve head blood flow

Diseases of the optic nerve head involving changes in blood flow are common. However, the pathophysiology is not always fully understood. Several non-invasive methods for measuring optic nerve head blood flow are available, but currently no gold standard has been established. Methods for measuring blood flow in optic neuropathies including colour Doppler imaging, retinal function imager, optical coherence tomography angiography and laser speckle flowgraphy are reviewed. Ultrasound colour Doppler imaging is a fast measurement technique where several different parameters, especially the blood flow velocity, can be calculated. Though used for many years in ophthalmology, its use is not standardized and it requires significant observer skills. The retinal function imager is a direct method where the haemoglobin in erythrocytes is visualized and blood flow velocities in retinal vessels are calculated from a series of photos. The technique is not suitable for direct measurement of blood flow within the optic nerve head. Laser speckle flowgraphy uses a laser light which creates a light scatter pattern in the tissue. Particles moving in the area causes changes in the speckle pattern from which a relative blood flow can be estimated. It is, however, not known whether optic nerve head microcirculation is measurable with the technique. Optical coherence tomography angiography uses multiple scans to evaluate blood flow with good reproducibility but often problems with artefacts. The technique is continuously being refined and increasingly used in research as a tool for the study of blood flow in retinopathies and optic neuropathies. Most of the conducted studies are based on small sample sizes, but some of the methods show promising results in an optic nerve head blood flow research setting. Further and larger studies are required to provide standardized and comparable measurements before one or more of the methods can be considered clinical helpful in daily practice.

The management of compensatory sweating after thoracic sympathectomy

OBJECTIVE

The main therapeutic method of treatment for local hyperhidrosis is endoscopic thoracic sympathectomy. Generally, resections of the sympathetic trunk or ganglia are performed between the second rib and sixth rib. However, this procedure can result in compensatory sweating, in which excess sweating occurs on the back, chest, and abdomen. Compensatory sweating has been regarded as a thermoregulatory response and thought to be untreatable. This study suggests that compensatory sweating is not a physiologic reaction and is indeed treatable.

METHODS

Eight patients with severe compensatory sweating were treated by observing blood perfusion of the skin with laser speckle flowgraphy, which determines the sympathetic nerves related to the area of skin with compensatory sweating. When intraoperative monitoring with laser speckle flowgraphy indicated the position of compensatory sweating by electrical stimulation of the sympathetic ganglion, ganglionectomy was performed.

RESULTS

The skin domain that each sympathetic nerve controls was able to be detected by laser speckle flowgraphy. In all patients, compensatory sweating was resolved after interruption of the ganglia or sympathetic nerves related to compensatory sweating.

CONCLUSIONS

Our results demonstrate that compensatory sweating is caused by denatured sympathetic nerves influenced by endoscopic thoracic sympathectomy and is not the result of a physiological response. With laser speckle flowgraphy, the sympathetic nerve related to the sweating of various parts of the body could be identified. The treatment of compensatory sweating on the back, chest, and stomach was previously considered to be difficult; however, compensatory sweating is demonstrated to be treatable with this technique.

Evaluation of blood flow on optic nerve head after pattern scan and conventional laser panretinal photocoagulation

To evaluate the changes in the blood flow on retina and the optic nerve head (ONH) after conventional laser treatment and to compare it to that after patterned scanning laser (PASCAL) treatment in patients with severe nonproliferative diabetic retinopathy (S-NPDR).In this prospective, cross-sectional study, the blood flow on retina and the ONH was assessed by laser speckle flowgraphy using the mean blur rate (MBR) in 39 eyes with S-NPDR before, 1, 4, 8, 12 weeks after panretinal photocoagulation (PRP). Of 39 eyes, 17eyes with 17 patients treated by conventional laser and 22 eyes with 22 patients treated by PASCAL.The mean age was 55.5 ± 11.5 years in the conventional laser group, 55.6 ± 11.8 years in the PASCAL group. The MBR-vessel, which can be dominantly expressed as retinal blood flow, was significantly reduced after PRP treated by conventional laser (P < .001), but did not change after PRP treated by PASCAL. The ratio of MBR-vessel to the baseline was significantly lower in the conventional laser group only at Week 1 (P = .045). The MBR-tissue, which can be dominantly expressed as the ONH blood flow, did not significantly change after PRP in the both group. The multiple stepwise regression analysis revealed that the laser burns was an independent factor significantly correlated with the ratio of MBR-vessel at Week 1 to the baseline (β = -0.550, P = .012).The retinal blood flow was significantly reduced during the 12 weeks only after completion of PRP by conventional laser treatment. Our results indicate that short pulse on PRP treatment performed by the PASCAL would not significantly reduce the retinal blood flow.

Laser speckle flowgraphy can also be used to show dynamic changes in the blood flow of the skin of the foot after surgical revascularization

Objectives

Laser speckle flowgraphy is a new method that enables the rapid evaluation of foot blood flow without contact with the skin. We used laser speckle flowgraphy to evaluate foot blood flow in peripheral arterial disease patients before and after surgical revascularization.

Materials and methods

A prospective single-center study. Thirty-one patients with 33 limbs that underwent surgical revascularization for peripheral arterial disease were included. Pre- and postoperative foot blood flows were measured on the plantar surface via laser speckle flowgraphy and skin perfusion pressure. The laser speckle flowgraphy device was used to visualize the blood flow distribution of the target skin and processed the pulse wave velocity of synchronized heart beats. The mean blood flow, which was expressed as the area of the pulse wave as the beat strength of skin perfusion on laser speckle flowgraphy converted into a numerical value, was assessed as dynamic changes following surgery. Beat strength of skin perfusion was also investigated in non-peripheral arterial disease controls (23 patients/46 limbs).

Results

The suitability of beat strength of skin perfusion in non-peripheral arterial disease controls was achieved; the beat strength of skin perfusion value was significantly higher in every area of interest in non-peripheral arterial disease controls compared to that in peripheral arterial disease limbs at the preoperative stage (105.8 ± 8.2 vs. 26.3 ± 8.2; P < 0.01). Although the pulse wave before surgery was visually flat in peripheral arterial disease patients, the pulse wave was remarkably and immediately improved through surgical revascularization. Beat strength of skin perfusion showed a dynamic change in foot blood flow (26.3 ± 8.2 at preoperation, 98.5 ± 6.7 immediately after surgery, 107.6 ± 5.7 at seven days after surgery, P < 0.01 for each compared to preoperation) that correlated with an improvement in skin perfusion pressure.

Conclusions

Laser speckle flowgraphy is a noninvasive, contact-free modality that is easy to implement, and beat strength of skin perfusion is a useful indicator of foot circulation during the perioperative period. Further analysis with a larger number of cases is necessary to establish appropriate clinical use.

Increased Microcirculation on Optic Nerve Head by Laser Speckle Flowgraphy at Early Stage of Leber Hereditary Optic Neuropathy

Leber hereditary optic neuropathy (LHON) is a mitochondrial disorder predominantly affecting young men. Characteristic features of an early stage of LHON are peripapillary telangiectatic microangiopathy with optic disc hyperaemia and swelling of the retinal nerve fibre layers. We evaluated the microcirculation of the optic nerve head (ONH) by laser speckle flowgraphy (LSFG) in a 79-year-old man and a 36-year-old woman with LHON. The ONH microcirculation of the tissue area was markedly increased in the early stage in both patients. LSFG may be a useful noninvasive method to suspect individuals to have an early stage of LHON.

Ocular microcirculation measurement with laser speckle flowgraphy and optical coherence tomography angiography in glaucoma

PURPOSE

To compare glaucoma severity with ocular microcirculation, measured with either laser speckle flowgraphy (LSFG) or optical coherence tomography angiography (OCTA).

METHODS

We retrospectively studied 82 eyes of 82 open-angle glaucoma (OAG) patients who underwent same-day LSFG and OCTA examinations, with 20 eyes of 20 healthy subjects as controls. In OCTA images, vessel density (VD) (%) was calculated in concentric regions (regions 1, 2 and 3: R1, R2 and R3, respectively) defined by 1.6-, 3.2- and 3.6-mm-diameter circles around the optic nerve head (ONH). In R3, the large vessels were automatically masked to calculate pure capillary density (auto R3 VD). LSFG-measured mean blur rate (MBR) was examined in the overall ONH (MA), vessel-area ONH (MV) and tissue-area ONH (MT).

RESULTS

Auto R3 VD had high reproducibility (coefficient of variation: 1.65-3.88%) and accurately reflected manual R3 VD [mean bias: -0.0087% (auto R3 VD - manual R3 VD)]. MA and MT decreased significantly with OAG severity, especially in the early OAG stages (control vs. mild: p = 0.003 and p < 0.001, respectively). R1 VD did not change with severity. R2 and auto R3 VD decreased significantly with OAG severity, especially in the severe stages (R2, mild vs. severe: p = 0.008; auto R3 VD, mild vs. severe: p < 0.001, moderate vs. severe: p = 0.028).

CONCLUSION

Optical coherence tomography angiography-derived auto R3 VD is novel, reproducible and accurately reflects manual measurements. It is useful for differentiating moderate and advanced glaucoma, while LSFG-derived MT is useful for identifying early glaucoma.

Factors associated with deep circulation in the peripapillary chorioretinal atrophy zone in normal-tension glaucoma with myopic disc

PURPOSE

To investigate factors associated with choroidal microcirculation in the peripapillary chorioretinal atrophy (PPA) zone in eyes with normal-tension glaucoma (NTG) and myopic disc.

METHODS

In 100 eyes of 100 NTG patients with myopic disc and 20 eyes of 20 age-matched myopic controls, 4.5 × 4.5 mm scans were made of the optic nerve head with optical coherence tomography angiography (OCTA). Peripapillary chorioretinal atrophy (PPA) area and PPA superficial choroidal image intensity (PPA-CI) were calculated with image j software. Clinical characteristics, laser speckle flowgraphy-measured mean blur rate in the temporal tissue area (temporal MT), the central thresholds (the averaged standard automated perimetry-measured visual field thresholds in the four paracentral points) and 3D-OCT-measured ganglion cell complex thickness in the papillomacular bundle (PMB-GCCT) were recorded.

RESULTS

The NTG patients had significantly lower intraocular pressure, PMB-GCCT and central threshold values, and a larger PPA area, than the controls. The area under the receiver operating characteristics curve to differentiate NTG with parafoveal scotoma (PFS) from controls was 0.76 for temporal MT, 0.85 for PPA-CI and 0.87 for PMB-GCCT. Univariate and multivariate analyses revealed that PPA-CI was negatively correlated with age, pulse rate, best-corrected visual acuity, axial length and PPA area, and positively correlated with temporal MT, PMB-GCCT and the central thresholds.

CONCLUSION

Peripapillary chorioretinal atrophy (PPA)-CI was associated with temporal MT, ageing, bradycardia, axial length elongation and changes in central retinal structure and visual function in patients with NTG and myopic disc. Thus, microcirculation deep within the PPA zone might be a clinically useful biomarker of PFS in NTG.

Preperimetric Glaucoma Prospective Study (PPGPS): Predicting Visual Field Progression With Basal Optic Nerve Head Blood Flow in Normotensive PPG Eyes

Purpose

To investigate the site specificity of visual field changes in eyes with normotensive preperimetric glaucoma (PPG), and to determine factors influencing visual field progression.

Methods

This prospective study comprised 84 eyes of 84 normotensive PPG patients followed for at least 16 months. Optic nerve head (ONH) blood flow was assessed with tissue-area mean blur rate (MBR_T), derived from laser speckle flowgraphy. Total deviation (TD) was measured in each sector of the Garway-Heath map to evaluate the site specificity of visual field loss. Subjects with a TD slope in the first quartile were classified as progressive, and other subjects as nonprogressive. Linear and multiple regression analyses were performed to determine factors affecting visual field progression.

Results

TD in the superior sector significantly decreased in the subjects overall during the follow-up periods (−0.48 ± 1.92 dB/y, P = 0.025). Linear regression analysis showed that basal MBR_T-inferior was correlated significantly with TD-superior slope (r = 0.332, P = 0.002). Furthermore, basal MBR_T was significantly lower in this sector in the progressive than the nonprogressive group (P = 0.010). Multiple linear regression analysis revealed that basal MBR_T-inferior was the only predictive factor for TD-superior slope (β = 0.329, P = 0.005).

Conclusions

These findings suggest that superior-sector visual field progression is most common in normotensive PPG eyes, and that reduced basal ONH blood flow is associated with visual field progression.

Translational Relevance

These findings provide new insight into the involvement of ONH blood flow impairment in glaucoma pathogenesis, and demonstrate the importance of assessing ONH blood flow to determine visual field progression in normotensive PPG.

Diurnal variation of pulse waveform parameters determined by laser speckle flowgraphy on the optic nerve head in healthy subjects

To investigate the diurnal variation of the pulse waveform parameters determined by laser speckle flowgraphy (LSFG) on the optic nerve head (ONH) in healthy subjects.This prospective cross sectional study was conducted at Nagoya University Hospital. We studied 13 healthy volunteers whose mean age was 33.5 ± 7.6 years. Eight pulse waveform parameters on the ONH were determined by LSFG (LSFG-NAVI) every 3 hours from 6 AM to 12 PM. The intraocular pressure (IOP), systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) in the brachial artery were also recorded. We evaluated the diurnal variations of the parameters and compared the pulse waveform parameters to the other parameters using a linear mixed model.Of the 8 parameters, skew (P < .001), blow out score (BOS, P < .001), blow out time (BOT, P = .028), rising rate (P < .001), falling rate (P < .001), resistivity index (P < .001) had a significant diurnal fluctuation. In addition, IOP (P < .001), SBP (P = .005), DBP (P = .001), and HR (P < .001) had significant diurnal fluctuations. The BOS and resistivity index were significantly correlated with the HR (P = .009, P = .012, respectively), and the BOT were significantly correlated with the DBP and mean ocular perfusion pressure (P = .042, P = .041, respectively).We found that there was significant diurnal variation in 6 waveform parameters on the ONH in LSFG. We believe that our results highlighting diurnal variations in these waveform parameters need to be considered when interpreting pulse waveform parameter data and in understanding the precise underlying mechanism of ocular diseases such as diabetic retinopathy, retinal vein occlusion, and glaucoma.

Evaluation of retinal blood flow before and after panretinal photocoagulation using pattern scan laser for diabetic retinopathy

PURPOSE

Laser speckle flowgraphy (LSFG) can measure blood flow in the ocular fundus. We analyzed the relationship between retinal blood flow and panretinal photocoagulation (PRP) in diabetic retinopathy.

METHODS

This retrospective observational study examined the eyes of 35 patients with proliferative diabetic retinopathy (PDR) or non-PDR (NPDR). PRP was performed using a pattern scan laser. Using LSFG, blood flow was evaluated as the mean blur rate (MBR) or the relative flow volume (RFV). We also evaluated MBR in the vessels of the optic nerve head (MBR-V), RFV at the first retinal artery (RFV-A), and RFV at the first retinal vein (RFV-V) before bifurcation. Blood flows were measured prior to treatment initiation, during each PRP session, and after PRP.

RESULTS

The total number of laser spots created was 4258 ± 461. Regression of neovascular activity at 6 months after PRP occurred in 29 (82.85%) eyes. MBR-V significantly decreased to 83.9 ± 16% (p = .0039), 79.3 ± 21% (p = .0001), and 73.5 ± 26% (p = .0001) after the first, second, and third PRP treatment sessions. MBR-V was also reduced to 75.0 ± 25% (p = .0001), 75.0 ± 25% (p = .0001), and 80.3 ± 22% (p = .0001) at 1, 3, and 6 months following PRP. During and at 6 months after the PRP treatments, RFV-A and RFV-V were also significantly reduced (p< .01).

CONCLUSIONS

During and after PRP treatments using pattern scan laser, retinal blood flow was reduced. Retinal blood flow may be an auxiliary measurement for effectively evaluating PRP or PDR.

Evaluation of optic nerve head blood flow in normal rats and a rodent model of non-arteritic ischemic optic neuropathy using laser speckle flowgraphy

PURPOSE

To evaluate optic nerve head (ONH) blood flow in normal rats and a rodent model of non-arteritic ischemic optic neuropathy (rNAION) in vivo using laser speckle flowgraphy (LSFG).

METHODS

Rats were under general anesthesia; to induce NAION, Rose Bengal (RB) was injected into the tail vein. After the administration of RB, the left ONH was photoactivated using an argon green laser. We measured ONH blood flow in the normal rats and the rNAION group (at 1, 3, 7, 14, and 28 days after the induction of NAION) using an LSFG-Micro. We used the mean blur rate (MBR) of the vessel region (MV) and MBR of the tissue region (MT) as indicators of blood flow. We compared the MBR of the right and left eyes in both the normal rats and the rNAION group.

RESULTS

In the normal rats, there were no significant differences in MV or MT between the right and left eyes. In the rNAION group, the MV and MT of the affected eyes were significantly lower than those of the unaffected eyes at all time points. There were significant differences between the left/right MV and MT ratios seen before the induction of NAION and those observed at 1, 3, 7, 14, and 28 days after the induction of NAION. However, there were no significant differences in these parameters among any of post-NAION induction time points.

CONCLUSION

Our results indicated that the ONH blood flow of the rNAION rats fell in the acute and chronic phases.

Association Between Optic Nerve Head Blood Flow Measured Using Laser Speckle Flowgraphy and Radial Arterial Pressure During Aortic Arch Surgery

OBJECTIVE

This study was designed to investigate the association between ocular blood flow measured using laser speckle flowgraphy (LSFG) and radial arterial pressure during aortic arch surgery.

DESIGN

A prospective study.

SETTING

A single university hospital.

PARTICIPANTS

This study included 24 patients undergoing aortic arch surgery with cardiopulmonary bypass (CPB) using antegrade selective cerebral perfusion (SCP).

INTERVENTIONS

Measurement of optic nerve head blood flow using LSFG and radial arterial pressure via a catheter in the radial artery METHODS AND MAIN RESULTS: Antegrade SCP was managed with 24℃ and 40-to-60 mmHg at the right radial artery, which usually corresponds to a flow rate of 10 mL/kg/min. Optic nerve head blood flow using LSFG and radial arterial blood pressure were evaluated simultaneously at the right side and recorded at the following 4 points: after the induction of anesthesia (phase 1), after the beginning of CPB (phase 2), after the beginning of antegrade SCP (phase 3), and after cessation of CPB (phase 4). A moderate positive correlation between %change of mean blur rate in the optic nerve head measured using LSFG and %change of radial mean arterial pressure was identified (r = 0.604, p < 0.001). Bland-Altman analysis showed that the bias (mean difference) was -1.2% (95% limits of agreement -47.4% to 45.0%), indicating good agreement between %changes of the values recorded using the 2 measurements.

CONCLUSIONS

Intraoperative monitoring of optic nerve head blood flow using LSFG can be used as an additional cerebral perfusion parameter during aortic arch surgery with CPB using antegrade SCP.

Differences in optic nerve head microcirculation between evening and morning in patients with coronary artery disease

PURPOSE

To determine whether differences or variation of blood flow in the ONH are independent risk factors for CAD.

METHODS

We studied 144 consecutive patients whose ocular blood flow in the ONH was measured in the evening and morning by LSFG. We analyzed the MBR throughout the ONH (MBR-A) and in the tissue (MBR-T) and vessels (MBR-V) in the ONH. We also evaluated the MBR-T, MBR-V, and MBR-A values obtained in the evening and morning and the variation (Δ) between evening and morning values in each group.

RESULTS

Twenty-three patients (16%) were diagnosed with CAD. The morning MBR-T and MBR-A values were significantly lower in these patients with CAD compared to the patients without CAD. ΔMBR-T in the CAD patients was significantly lower compared to that of the no-CAD patients. The logistic regression analysis was revealed that a high carotid artery plaque score, lower ΔDBP, and ΔMBR-T were identified as risk factors for CAD.

CONCLUSIONS

Ocular microcirculation obtained from LSFG may provide a window for detecting changes in microvasculature related to CAD.

The reduction of temporal optic nerve head microcirculation in autosomal dominant optic atrophy

PURPOSE

To evaluate the optic nerve head (ONH) microcirculation in autosomal dominant optic atrophy (ADOA) patients.

METHODS

This study comprised 22 eyes of 12 ADOA patients, diagnosed according to clinical findings including family history and the presence of mutations in the OPA1 gene. Twenty-four normal eyes of 24 age-matched subjects, with either the right or left eye randomly selected for use, served as controls. Circumpapillary retinal nerve fibre layer thickness (cpRNFLT) and mean blur rate (MBR) in the ONH were determined with optical coherence tomography (OCT) and laser speckle flowgraphy (LSFG), respectively. For each ONH quadrant (superior, temporal, inferior and nasal), the MBR and cpRNFLT ratio was also calculated by dividing tissue MBR in that quadrant by tissue MBR in the entire ONH and by dividing cpRNFLT in that quadrant by cpRNFLT in the entire ONH respectively.

RESULTS

Mean blur rate (MBR) in all quadrants was significantly lower in the ADOA patients than in the controls (p < 0.001 in each). The MBR ratio was significantly lower in the ADOA patients only in the temporal quadrant (p < 0.001). Similarly, cpRNFLT was lower in the ADOA patients in all quadrants (p < 0.001 in each), and the cpRNFLT ratio was lower in the temporal quadrant (p < 0.001).

CONCLUSION

Reduced blood flow in the temporal optic disc in ADOA patients is associated with reduced temporal cpRNFLT, suggesting that both are caused by damage to the papillomacular bundle. The anatomical characteristics of the papillomacular bundle may make it especially susceptible to mitochondrial dysfunction-induced damage, which occurs in ADOA.

Choroidal circulation impairment during the anterior recurrence of Vogt-Koyanagi-Harada disease confirmed with indocyanine green angiography and laser speckle flowgraphy

PURPOSE

To assess choroidal inflammation-related circulatory changes associated with the anterior recurrence of Vogt-Koyanagi-Harada (VKH) disease, using indocyanine green angiography (ICGA) and laser speckle flowgraphy (LSFG).

METHODS

This retrospective case series included 17 eyes of 11 patients with VKH disease showing recurrent inflammatory findings in the anterior, but not posterior, segment (i.e. anterior recurrence). Indocyanine green angiography (ICGA) and LSFG were performed at the time of recurrence and one month after the initiation of corticosteroid therapy. The number and total area of hypofluorescent dark dots (HDDs) on ICGA were independently counted by three physicians and measured with ImageJ, respectively. Mean blur rate (MBR), a quantitative index of relative blood flow velocity, was calculated via the LSFG Analyzer software.

RESULTS

Hypofluorescent dark dots (HDDs) were identified on ICGA in 13 of 17 eyes (76%) with the anterior recurrence of VKH disease. The number and total area of HDDs significantly decreased from 203 ± 101 dots to 59 ± 51 dots and from 48 789 ± 24 251 pixels to 15 664 ± 13 254 pixels, respectively. The change ratio of MBR significantly increased by 17.9 ± 16.3% after the treatment. Importantly, there was no significant association between the change ratios of HDDs and MBR.

CONCLUSIONS

These findings on LSFG and ICGA clearly demonstrated subclinical involvement as well as post-treatment improvement of choroidal circulation impairment due to granulomatous inflammation in eyes with the anterior recurrence of VKH disease. The present data suggest the validity of using these two examinations, capable of detecting different circulatory changes, in the management of recurrent VKH disease.

Autoregulation of Optic Nerve Head Blood Flow Induced by Elevated Intraocular Pressure during Vitreous Surgery

PURPOSE

To investigate optic nerve head (ONH) blood flow changes resulting from intraocular pressure (IOP) elevation in subjects without systemic disorders.

MATERIALS AND METHODS

Eighteen eyes of 18 patients who underwent vitrectomy to treat an epiretinal membrane or macular hole at Toho University Sakura Medical Center were included. Following standard 25-gauge microincision vitreous surgery, mean blur rate (MBR) in tissue (MT), an index of ONH blood flow, was measured using laser speckle flowgraphy. Measurements were taken before and 5 and 10 minutes after a 15 mmHg IOP elevation.

RESULTS

The ONH blood flow was initially lower than baseline (P = 0.001) after elevating IOP from 14.8 ± 2.8 mmHg to approximately 30 mmHg. Between 5 and 10 minutes after elevating IOP, ONH blood flow partially recovered (P = 0.004), even though ocular perfusion pressure was 20.2% lower than at baseline.

CONCLUSIONS

The ONH blood flow in subjects without systemic disorders was initially lower, but began to recover 5-10 minutes after a 15 mmHg elevation in IOP. These results indicate that autoregulatory mechanisms of ONH blood flow may help to minimize the effects of IOP elevations and fluctuations during vitreous surgery.

What ocular and systemic variables affect choroidal circulation in healthy eyes

The aim of the study was to investigate the relationship between choroidal blood flow and systemic and ocular variables in patients with healthy eyes.In this prospective cross-sectional study, we examined 241 eyes of 241 healthy Japanese subjects (92 males and 149 females; mean age, 37.8 ± 17.0 years). The mean blur rate, a measure of the relative blood flow of the choroid, was determined using laser speckle flowgraphy. The total cross-sectional choroidal, luminal, and stromal areas of the choroid were determined by the binarization method. We investigated the correlation between choroidal MBR and systemic and ocular variables.Choroidal mean blur rate correlated with age (r = -0.385, P < 0.001) and choroidal thickness (r = 0.264, P < 0.001). The choroidal area correlated with choroidal mean blur rate (r = 0.374, P < 0.001), age (r = -0.184, P = 0.004), axial length (r = -0.251, P < 0.001), and choroidal thickness (r = 0.468, P < 0.001). The luminal area correlated with choroidal mean blur rate (r = 0.403, P < 0.001), age (r = -0.244, P < 0.001), axial length (r = -0.218, P = 0.001), and choroidal thickness (r = 0.435, P < 0.001). On multiple stepwise regression analyses, age (β = -0.321, P < 0.001) and luminal area (β = 0.320, P < 0.001), heart rate (β = 0.136, P = 0.018), and mean ocular perfusion pressure (β = 0.126, P = 0.045) were independent factors indicating the choroidal mean blur rate. Furthermore, axial length (β = -0.352, P < 0.001), choroidal mean blur rate (β = 0.273, P < 0.001), age (β = -0.247, P < 0.001), gender (β = -0.226, P < 0.001), and mean ocular perfusion pressure (β = 0.193, P = 0.002) were independent factors indicating the luminal area.The choroidal blood flow positively correlated with the luminal area and negatively correlating with age. In addition, the luminal area was negative correlated with age. It is suggested that aging causes a reduction in choroidal blood flow and luminal area, and as a result of aging effect, decreased choroidal blood flow would correlate with decreased luminal area.

Correlation between macular blood flow and central visual sensitivity in retinitis pigmentosa

PURPOSE

To investigate the changes in macular blood flow and the correlation between those changes and central visual function in patients with retinitis pigmentosa (RP).

METHODS

The mean blur rate (MBR), a quantitative blurring index of the laser speckle pattern that represents retinal and choroidal blood flow, was measured by laser speckle flowgraphy. Mean blur rate values in the macular area were compared between 70 patients with RP and 28 control subjects. The relationships between MBR on the one hand and, on the other, visual acuity (VA), mean deviation (MD) and averaged macular sensitivity of static perimetry tests (Humphrey Filed Analyzer, the central 10-2 program) were analysed in patients with RP.

RESULTS

Macular MBR was decreased to 75% in patients with RP compared with control subjects (p < 0.0001, Student's t-test). Spearman's rank testing showed that macular MBR was significantly correlated with VA (r = -0.261, p = 0.0299), MD values (r = 0.438, p = 0.0002) and averaged macular sensitivity at the central 4 and 12 points of static perimetry tests (r = 0.426 and 0.442, p = 0.0003 and 0.0002, respectively). Multivariable-adjusted analysis confirmed that MBR was independently associated with MD (p = 0.0002) and macular sensitivity at the central 4 and 12 points (p < 0.0001 and 0.0002, respectively).

CONCLUSIONS

Decreased macular blood flow was associated with reduced macular visual sensitivity in patients with RP. Although the cause-effect relationships remain to be elucidated, these findings suggest that vascular defects may be involved in the pathogenesis of RP such as central vision loss.

Laser speckle and hydrogen gas clearance measurements of optic nerve circulation in albino and pigmented rabbits with or without optic disc atrophy

PURPOSE

The purpose of this study was to evaluate the correlation between laser speckle flowgraphy measurements of mean blur rate (MBR) and hydrogen gas clearance measurements of capillary blood flow (CBF) in the optic nerve head (ONH) of albino and pigmented rabbits, with or without chronic ischemia-induced ONH atrophy.

METHODS

The ONH MBR and ONH CBF were measured at baseline, 30 and 60 minutes after the intravenous administration of endothelin-1 (ET-1) (10(-10) mol/kg) in six albino and six pigmented rabbit eyes. The ONH MBR and ONH CBF were also measured in nine pigmented rabbit eyes that underwent the intravitreal administration of ET-1 (20 pmol) twice per week for 4 weeks to provoke chronic ischemia-induced ONH atrophy.

RESULTS

In the group that received intravenous ET-1, average measurements of ONH MBR and ONH CBF at all time points were correlated in both the albino (r = 0.88, P < 0.001, n = 18) and pigmented rabbits (r = 0.85, P < 0.001, n = 18), with no intrarabbit correlations (P = 0.524). The ONH MBR and ONH CBF were also correlated in the model of chronic ischemia-induced ONH atrophy (r = 0.78, P = 0.013, n = 9). Pooled ONH MBR and ONH CBF measurements in both the intravenous and intravitreal groups were also highly correlated (r = 0.87, P < 0.001, n = 45), with no significant intergroup differences in the relationship between ONH MBR and ONH CBF (P = 0.138).

CONCLUSIONS

Regardless of the presence of fundus pigmentation or ONH atrophy, ONH MBR and ONH CBF were highly correlated, suggesting that MBR in the ONH tissue is usable for interindividual and intergroup comparisons.