Peripapillary Retinal Nerve Fiber Layer Vascular Microcirculation in Glaucoma Using Optical Coherence Tomography-Based Microangiography

Association of retinal microvascular curve tortuosity and multiple sclerosis: A cross-section analysis from the UK Biobank

BACKGROUND

There is growing evidence supporting that vascular abnormalities contribute to multiple sclerosis (MS), and retinal microvasculature functions as a visible window to observe vessels. We hypothesized that retinal vascular curve tortuosity is associated with MS, which this study aims to address.

METHODS

Participants from the UK Biobank with complete clinical records and gradable fundus photos were included in the study. Arteriolar and venular curve tortuosity and vessel area density are quantified automatically using a deep learning system. Individuals with MS were matched to healthy controls using propensity score matching (PSM). Conditional logistic regression was used to investigate the association between retinal vascular characteristics and MS. We also used a receiver operating characteristic (ROC) curve to assess the diagnostic performance of MS.

RESULTS

Venular curve tortuosity (VCT) was found to be significantly associated with MS. And patients with multiple sclerosis were probable to have lower VCT than the non-MS group (OR = 0.22 [95 % CI, 0.05 to 0.92], P < 0.05).

CONCLUSIONS

Our study reveals a significant association between vessel curve tortuosity and MS. The lower curve tortuosity of the retinal venular network may indicate a higher risk of incident multiple sclerosis.

Diagnostic ability of the combination of retinal microvasculature evaluation and static automated perimetry for early primary open-angle glaucoma

PURPOSE

To investigate the diagnostic ability of retinal superficial vasculature evaluation by optic coherence tomography angiography (OCTA) combined with visual field (VF) testing for early primary open-angle glaucoma (POAG).

PATIENTS AND METHODS

In this cross-sectional study, 84 participants were included, including 11 in the ocular hypertension (OHT) group, 11 in the preperimetric POAG (pre-POAG) group, 29 in the early POAG group and 33 in the control group. All participants underwent 6 × 6 mm2 scans of macula and optic nerved head by optic coherence tomography (OCT) and OCTA, along with white-on-white and blue-on-yellow VF testing by static automated perimetry. The ability of diagnosing early glaucoma by either various examinations separately or combination of examinations in both terms of function and structure was studied using the receiver operating characteristic (ROC) curve and the area under the curve (AUC).

RESULTS

The superficial retinal vessel densities (VD) in peri-nasal, para-temporal, peri-temporal and peri-inferior regions around the macula, as well as vessel area densities (VAD) in all peripapillary regions, were significantly different among the four groups, with lower VD or VAD in the early POAG patients compared to the normal individuals. The diagnostic ability of peripapillary superficial retinal VAD alone or VF testing alone was limited for early POAG only. However, the combination of these two was more effective in distinguishing normal individuals from OHT subjects or pre-POAG patients without VF defects, with better performance than the combination of peripapillary retinal nerve fiber layer (RNFL) thickness and VF indicators.

CONCLUSIONS

Peripapillary retinal vessel densities were generally lower in early POAG patients compared to normal individuals. The combination of peripapillary superficial retinal VAD by OCTA with white-on-white VF testing improved the ability to distinguish POAG patients at early stage without function impairment, which may help in providing reference and guidance for the following-up and treatment of suspected POAG patients.

Efficacy and safety of platelet-rich plasma for acute nonarteritic anterior ischemic optic neuropathy: a prospective cohort study

Background

As the most common acute optic neuropathy in older patients, nonarteritic anterior ischemic optic neuropathy (NAION) presents with varying degrees of visual acuity loss and visual field defect. However, there is no generally accepted treatment for NAION.

Objectives

To evaluate the efficacy and safety of platelet-rich plasma (PRP) for patients with acute NAION within 2 months.

Design

A prospective, nonrandomized controlled trial.

Methods

Twenty-five eyes of 25 patients were enrolled. Of them, 13 received anisodine hydrobromide and butylphthalide-sodium chloride injection continuously for 10 days as basic treatment in the control group, and 12 received two tenon capsule injections of PRP on a 10 days interval as an additional treatment in the PRP group. We compared the best-corrected visual acuity (BCVA) and capillary perfusion density (CPD) of radial peripapillary capillaries and the moth-eaten eara of the peripapillary superficial capillary plexus and deep capillary plexus at 1 day (D1) before the first PRP treatment and 7 days (D7), 14 days (D14), and 30 days (D30) after the first PRP injection. Ocular and systemic adverse effects were assessed.

Results

In the PRP group, a better BCVA occurred at D30 (adjusted p = 0.005, compared with D1, recovered from 0.67 ± 0.59 to 0.43 ± 0.59), and a significant improvement in CPD was observed at D30 (adjusted p < 0.001, p = 0.027, p = 0.027, compared with D1, D7, D14, in sequence, the value was 35.97 ± 4.65, 38.73 ± 4.61, 39.05 ± 5.26, 42.71 ± 4.72, respectively). CPD at D7 in the PRP group was better than that in the control group (p = 0.043). However, neither BCVA nor the moth-eaten area index were significantly different (all p > 0.5) between the two groups. The main adverse effect was local discomfort resolved within 1 week, and no other systemic adverse events occurred.

Conclusion

Tenon capsule injection of PRP was a safe treatment for AION and could improve capillary perfusion of the optic nerve head and might be helpful in increasing short-term vision in patients with acute NAION.

Peripapillary Perfusion Analysis Using Optical Coherence Tomography Angiography in Patients with Normal Tension Glaucoma

PURPOSE

This study aimed to assess the difference in the vascular parameters of perfusion in the optic nerve head in normal tension glaucoma (NTG) across disease stages using optical coherence tomography angiography and its correlation with peripapillary retinal nerve fiber layer (RNFL) thickness.

METHODS

In this retrospective study, 83 eyes with varying stages of NTG (25 mild, 31 moderate, and 27 severe) and 90 healthy eyes were enrolled. The perfusion density (PD) and flux index (FI) of the optic nerve head divided into four sectors were determined. We compared the vascular, structural, and functional parameters between normal and glaucomatous eyes and performed a subgroup analysis among the NTG stages. Pearson correlation coefficient was used to assess the topographic correlation between vascular parameters and RNFL thickness.

RESULTS

PD and FI were significantly decreased in the NTG group. Subgroup analysis revealed a significant decrease in vascular parameters in most regions in the NTG group, except for the nasal PD and temporal FI. Post hoc analysis showed a significant decrease in PD in the inferior region across all severity levels (mild vs. moderate, p = 0.012; moderate vs. severe, p = 0.012; mild vs. severe, p < 0.001). PD and FI were strongly correlated with RNFL thickness in all quadrants (all p < 0.001), with the strongest correlation observed in the inferior region.

CONCLUSIONS

Vascular parameters were significantly decreased in glaucomatous eyes, and the degree of decrease in vascular parameters was proportional to glaucoma severity. Peripapillary perfusion analysis using optical coherence tomography angiography may complement other measurements used for glaucoma diagnosis.

Vessel Density Features of Optical Coherence Tomography Angiography for Classification of Glaucoma Using Machine Learning

PRCIS

Machine learning (ML) based on the optical coherence tomography angiography vessel density features with different thresholds using a support vector machine (SVM) model provides excellent performance for glaucoma detection.

BACKGROUND

To assess the classification performance of ML based on the 4 vessel density features of peripapillary optical coherence tomography angiography for glaucoma detection.

METHODS

Images from 119 eyes of 119 glaucoma patients and 76 eyes of 76 healthy individuals were included. Four vessel density features of optical coherence tomography angiography images were developed using a threshold-based segmentation method and were integrated into 3 models of machine learning classifiers. Images were divided into 70% training set and 30% test set. Classification performances of SVM, random forest, and Gaussian Naive Bayes models were evaluated with the area under the receiver operating characteristic curve (AUC) and accuracy.

RESULTS

Glaucoma eyes had lower vessel densities at different thresholds. For differentiating glaucoma eyes, the best results were achieved with 70% and 100% thresholds, in which SVM classifier discriminated glaucoma from healthy eyes with an AUC of 1 and accuracy of 1. After SVM, the random forest classifier with 100% thresholds showed an AUC of 0.993 and an accuracy of 0.994. Furthermore, the AUC of our ML performance (SVM) was 0.96 in a subgroup analysis of mild and moderate glaucoma eyes.

CONCLUSIONS

ML based on the combined peripapillary vessel density features of total vessels and capillaries in the whole image and ring image could provide excellent performance for glaucoma detection.

Optical Coherence Tomography Angiography (OCTA) Differences in Vessel Perfusion Density and Flux Index of the Optic Nerve and Peri-Papillary Area in Healthy, Glaucoma Suspect and Glaucomatous Eyes

Purpose

To assess the ability of vascular perfusion parameters determined by optical coherence tomography angiography (OCTA) to detect and monitor glaucoma.

Methods

This prospective study included healthy, glaucoma suspect and glaucomatous eyes. All eyes underwent comprehensive glaucoma examination, including visual field tests and ocular imaging scans by OCTA. Parameters measured included retinal nerve fiber layer (RNFL) thickness, ganglion cell analysis (GCA), vascular perfusion density (VPD) and flux index (FI) of the optic nerve and peri-papillary area. Ocular parameters in healthy, glaucoma suspect, and glaucomatous eyes were compared by generalized estimating equations (GEE) with adjustments for age, with their relationships analyzed by Pearson's correlation coefficient. Rates of change per year were compared in glaucomatous eyes with and without glaucoma progression.

Results

This study enrolled 238 eyes, including 56 healthy, 79 glaucoma suspect, and 103 glaucomatous eyes. After adjustments for age, the average VPD (45.40 ± 0.19% vs 45.05 ± 0.22% vs 42.89 ± 0.32%, p < 0.001) and FI (0.4210 ± 0.0055 vs 0.4105 ± 0.0039 vs 0.3801 ± 0.0048, p < 0.001) in these three groups differed significantly. Average VPD in the glaucoma group was inversely associated with the severity of glaucoma, being 43.99 ± 0.32%, 42.63 ± 0.43% and 39.27 ± 0.48% in eyes with early, moderate and severe glaucoma, respectively (p < 0.001). Average VPD, as well as VPD in the superior and inferior quadrants correlated well with both OCT determined RNFL and visual field parameters. The decreases per year in both superior (-0.012 vs -0.001, p = 0.002) and inferior (-0.008 vs -0.003, p = 0.007) FI were significantly greater in glaucomatous eyes with than without glaucoma progression.

Conclusion

Both VPD and FI as measured by OCTA are promising ocular parameters that can distinguish between normal and glaucomatous eyes. VPD is sensitive in comparing eyes at different glaucoma stages, whereas FI can detect rates of glaucoma progression.

Trial Registration

Thai Clinical Trial Registry, TCTR20181031002.

Optical Coherence Tomography Angiography of the Retinal Circulation Following Trabeculectomy for Glaucoma

PRCIS

Despite successful trabeculectomy, eyes with similar levels of peripapillary and macular vessel densities but with worse preoperative visual field mean deviations may experience functional and vascular decline after surgery.

PURPOSE

To evaluate the retinal microcirculation change after trabeculectomy according to glaucoma severity using optical coherence tomography angiography (OCTA).

METHODS

We enrolled 59 eyes of primary open angle glaucoma patients who underwent trabeculectomy. The eyes were categorized into 3 groups by preoperative visual field (VF) mean deviation (MD), group 1: MD>-12.0 dB, group 2: MD -12.0 to -20.0 dB, and group 3: MD <-20.0 dB. OCTA was performed preoperatively and 1 year after trabeculectomy. The differences in the radial peripapillary capillary vessel density (pVD) and macular VD between preoperative and postoperative assessment were analyzed and compared in each group. Factors associated with the VD change after trabeculecomy were determined using linear regression analysis.

RESULTS

Mean postoperative IOP and IOP reduction did not differ among the 3 groups after trabeculectomy. Preoperative pVD (37.2 vs. 36.6%, P =1.00) and macular VD (39.0 vs. 38.4%, P =1.00) did not differ between groups 1 and 2. Group 1 and 3 showed no changes in VD parameters after trabeculectomy (all, P >0.05). However, group 2 showed statistically significant decreases in pVD (36.6 vs. 32.9%, P <0.001) and macular VD (38.4 vs. 36.0%, P =0.010) after trabeculectomy. The reduction of pVD was associated with a decrease of IOP (Coefficient (β); 0.14, P =0.032) and VF MD (β; 0.15, P =0.0116) in group 2, respectively.

CONCLUSION

Following successful trabeculectomy surgery for uncontrolled glaucoma with similar IOP reduction, glaucoma eyes with advanced visual field loss showed reduced pVD and macular VD measured by OCT-A. These findings may be relevant to disease progression.

Peripapillary and macular vascular parameters by optical coherence tomography angiography in primary congenital glaucoma

OBJECTIVE

To evaluate the differences in peripapillary and macular vascular parameters by optical coherence tomography angiography (OCTA) between patients with primary congenital glaucoma (PCG) and healthy controls; and to determine their diagnostic accuracy.

MATERIAL AND METHODS

Observational, cross-sectional study including 39 eyes with PCG and 78 healthy eyes. Only one eye per patient was included. All included patients underwent a comprehensive ophthalmic examination and peripapillary and macular analysis were performed by AngioplexTM OCTA (Cirrus HD-OCT 5000) with a 4.5 × 4.5 mm optic nerve head scan and 6 × 6 mm macular scan. Global data and quadrant data from peripapillary vascular parameters and global data and circular sectors data from macular superficial plexus parameters were compared between groups. The glaucoma discrimination capability of these parameters was calculated as areas under the receiver operating characteristics curve (AUC ROC).

RESULTS

Mean age was 14.1 ± 8.7 years for the PCG patients and 11.7 ± 6.2 years for controls (p = 0.093). All vascular peripapillary measurements (global and quadrants; all p < 0.001) and all macular measurements (p < 0.042) excepting perfusion density in the inner circle (p = 0.087), were reduced in the PCG group compared to controls. According to AUC ROC, peripapillary (all ≥ 0.706) and macular parameters (all ≥ 0.699) showed good diagnostic capacity. AUC ROC for the most discriminatory measurements corresponding to blood flux index (0.887) and whole macula vascular density (0.855) were similar (p = 0.085).

CONCLUSION

Peripapillary and macular vascular parameters by OCTA are decreased in patients with PCG, showing a good capacity to discriminate between normal and glaucomatous eyes.

Fractal Dimension of Peripapillary Vasculature in Primary Open-Angle Glaucoma

PURPOSE

To compare the fractal dimensions of the peripapillary microvasculature as obtained by optical coherence tomography angiography (OCTA) between primary open-angle glaucoma (POAG) and controls.

METHODS

Optic nerve head and peripapillary area images were taken using the 20° × 20°-scan of Spectralis OCTA (Heidelberg Engineering) in 97 subjects (64 POAG patients, 33 control patients). The optic nerve head microvasculature was evaluated according to predefined slabs: the superficial vascular complex (SVC) and the avascular complex (AVC). The en face image of each slab was processed by ImageJ software (National Institutes of Health) in order to calculate the vessel density and the fractal dimension using the box-counting method. For comparison, the peripapillary retinal nerve fiber layer (RNFL) thickness was obtained from Spectralis OCT circle scans. The utilities of the parameters for discriminating between the POAG and control groups were assessed using areas under the receiver operating characteristic curves (AUCs).

RESULTS

The SVC fractal dimension was lower in the POAG than in the control group (p < 0.001), while AVC showed no intergroup difference (p = 0.563). The fractal dimension showed a good correlation with the vessel density in both SVC and AVC (both p < 0.001). In a multivariable regression analysis, the SVC fractal dimension was negatively correlated with age (p < 0.001) and axial length (p < 0.001) and positively correlated with average RNFL thickness (p < 0.001), while the AVC fractal dimension was positively correlated with the Bruch's membrane opening size (p = 0.013). In terms of diagnostic utility, the AUC was significantly larger for the average RNFL thickness (AUC, 0.889) than for the SVC fractal dimension (AUC, 0.772; p = 0.008).

CONCLUSIONS

The fractal dimension of SVC was associated with the average RNFL thickness and was reduced in POAG patients. Fractal dimension analysis could be used in evaluating peripapillary vascularity by OCTA.

Correlation between OCT-angiography and photopic negative response in patients with primary open angle glaucoma

Purpose

To evaluate the association between OCT-angiography (OCTA) and photopic negative response (PhNR) in open angle glaucoma (OAG) patients and assess the diagnostic accuracy of these parameters in early detection of glaucoma.

Methods

A total of 152 eyes were enrolled in this study, 28 eyes with mild POAG (group I), 44 eyes with moderate-severe POAG (group 2) & 80 eyes of healthy subjects (control group). Full ophthalmological examination, OCTA and PhNR measurements were underwent for all participants. RNFL, GCC thicknesses, PhNR (implicit time and amplitude) were recorded. The superficial and deep capillary plexus vessel density (SCP-VD%, DCP-VD%) were measured by using 6 × 6 mm macula OCTA scans. The peripapillary vessel density (RPC-VD %) were measured by using 4.5 × 4.5 mm optic disk head OCTA scans.

Results

There were reduction of the median Interquartile range (IQR) thickness of the GCC and RNFL in OAG eyes versus normal (P < 0.001). RPC-VD%, SCP-VD % and DCP-VD% were significantly reduced in OAG eyes versus normal (P < 0.001). Increased OAG severity was associated with more reduction in PhNR amplitude and increased implicit time. Reduced PhNR amplitude and prolonged latency were significantly correlated with reduced vascular parameters. The RCP-VD and PhNR amplitude demonstrated higher diagnostic accuracy (98.7) with the largest AUC and higher sensitivity and specificity (100% & 98.7%, respectively), followed by the PhNR implicit time with (AUC = 0.995) with a diagnostic accuracy 98.7. The SCP-VD, RNFL and GCC thickness had a diagnostic accuracy of (75.0, 81.6 & 84.2), respectively (P < 0.001).

Conclusions

OCTA vascular parameters displayed significant positive correlation with PhNR amplitude and significant negative correlation with PhNR implicit time. OCTA and PhNR parameters showed a high diagnostic accuracy for detection of glaucoma, and both may provide promising insight in early detection of glaucoma.

This study was retrospectively registered on ClinicalTrials.gov (identifier, NCT05104294).

Analysis of retinal vasculature changes in indirect traumatic optic neuropathy using optic coherence tomography angiography

AIM

To assess the retinal vasculature alterations in indirect traumatic optic neuropathy (ITON) patients following craniofacial trauma by optic coherence tomography angiography (OCTA).

METHODS

Patients diagnosed of monocular ITON were recruited from August 2016 to May 2020. OCTA was performed using the AngioVue OCT-A system for two cube scans centered at the optic nerve head and fovea. OCTA data included thicknesses of peripapillary retinal nerve fiber layer (RNFL) and macular ganglion cell complex (GCC), as well as proportion of capillary perfusion and data were analyzed for correlation with post-injury timepoints: within 7, 8-30, 31-90, and 91-365d.

RESULTS

A total of 73 ITON patients were studied. Significant thinning of RNFL and GCC layers and attenuation of microvascular perfusion were observed in ITON eyes as compared to contralateral unaffected eyes (for most of the analyzed sectors and quadrants, P<0.05). Without respect to surgical intervention and vision recovery, the decrease in retinal layer thicknesses and microvascular perfusion was time-dependent, and most significant within three months (P<0.001).

CONCLUSION

ITON presents with time-dependent thinning of retinal layers and attenuation of microvasculature, indicating possible degeneration of retinal ganglion cells due to reduced retinal blood supply.

Depth-resolved extraction of optical attenuation for glaucoma assessment in clinical settings: a pilot study

We assessed the ability of the optical attenuation coefficient (AC) to detect early-stage glaucoma with two AC estimation algorithms: retinal layer intensity ratio (LIR) and depth-resolved confocal (DRC). We also introduced new depth-dependent AC parameters for retinal nerve fiber layer assessment. Optical coherence tomography B-scans were collected from 44 eyes of age-similar participants with eye health ranging from healthy to severe glaucoma, including glaucoma suspect patients. Mean AC values estimated from the DRC method are comparable to ratio-extracted values (p > 0.5 for all study groups), and the depth-dependent AC_DRC parameters enhance the utility of the AC for detection of early-stage glaucoma.

Repeatability and Reproducibility of 4.5 by 4.5 mm Peripapillary Optical Coherence Tomography Angiography Scans in Glaucoma and Nonglaucoma Eyes

PRCIS

Peripapillary vessel parameters from optical coherence tomography angiography (OCTA) 4.5×4.5 mm scans in nonglaucomatous and glaucomatous eyes showed high repeatability and reproducibility, with higher reliability for commercially developed OCTA parameters compared with custom OCTA parameters.

PURPOSE

The purpose of this study was to assess intrasession repeatability versus intersession reproducibility of peripapillary vessel parameters from 4.5×4.5 mm OCTA scans in nonglaucomatous eyes and glaucomatous eyes.

MATERIALS AND METHODS

In a longitudinal study, peripapillary OCTA scans were quantified using research-oriented custom quantification software that calculated vessel area density (VAD) and flux and clinic-oriented commercially developed software (Cirrus 11.0) that calculated perfusion density (PD) and flux index (FI). Intrasession repeatability and intersession reproducibility were evaluated using within-eye coefficient of variation (CVW) and intraclass correlation coefficient (ICC).

RESULTS

With 127 nonglaucomatous eyes, intrasession CVW for VAD, PD, flux, and FI were 1.900%, 1.174%, 2.787%, and 1.425%, respectively. The intersession CVW were 2.039%, 1.606%, 4.053%, and 2.798%, respectively. Intrasession ICC ranged from 0.903 to 0.956, and intersession ICC ranged from 0.850 to 0.896. Among 144 glaucomatous eyes, intrasession CVW for VAD, PD, flux, and FI were: 3.841%, 1.493%, 5.009%, and 2.432%, respectively. The intersession CVW were 4.991%, 2.155%, 6.360%, and 3.458%, respectively. Intrasession ICC ranged from 0.956 to 0.969, and intersession ICC ranged from 0.918 to 0.964.

CONCLUSIONS

Among nonglaucomatous and glaucomatous eyes, the majority of peripapillary OCTA vessel parameters from 4.5×4.5 mm scans had greater intrasession repeatability than intersession reproducibility. There was a greater agreement for the commercially developed quantification parameters than for their custom quantification counterparts.

Quantitative Analysis of Radial Peripapillary Capillary Network in Patients With Papilledema Compared with Healthy Subjects Using Optical Coherence Tomography Angiography

BACKGROUND

To quantitatively compare the peripapillary microvascular network between patients with papilledema and healthy subjects using swept source optical coherence tomography angiography.

METHODS

In this retrospective observational study, patients with papilledema secondary to idiopathic intracranial hypertension and healthy controls were imaged with swept source optical coherence tomography angiography (PLEX Elite 9000; Carl Zeiss Meditec, Dublin, CA) using a 6 × 6 mm scan pattern centered on the optic disc. The capillary perfusion density (CPD) and capillary flux index (CFI) of the radial peripapillary capillaries in the retinal nerve fiber layer (RNFL) were calculated using Zeiss algorithm.

RESULTS

Thirty-nine eyes of 20 patients with papilledema and 66 eyes of 33 healthy subjects were imaged. The mean (P < 0.01), superior (P < 0.01), inferior (P < 0.01), and temporal (P = 0.02) CPD significantly differed between both groups. No significant difference was found between both groups for the CFI. The mean (P < 0.01), superior (P < 0.01), inferior (P = 0.01), temporal (P < 0.01), and nasal (P < 0.01) quadrants of the RNFL were positively associated with the CFI. The mean (P < 0.01), superior (P = 0.01), inferior (P = 0.01), temporal (P < 0.01), and nasal (P = 0.01) quadrants of the RNFL were negatively associated with the CPD.

CONCLUSION

Our study showed a decreased peripapillary capillary density without changes in flux intensity in eyes with papilledema. There were a positive association between the CFI and the RNFL and a negative association between the CPD and the RNFL. It confirmed the discriminatory ability of OCTA in differentiating a papilledema secondary to IIH from a normal optic disc, while providing complementary information for understanding papilledema pathophysiology.

Comparison of the Structure-Function Relationship in Glaucoma Using Optical Microangiography in the Peripapillary Retinal Nerve Fiber Layer

PRCIS

Optical microangiography measurements correlated with functional parameters in glaucoma patients. Optical coherence tomography angiography-derived vessel perfusion density (VPD) better reflected the structure-function relationship than flux index (FI) and retinal nerve fiber layer thickness.

PURPOSE

The purpose of this study was to compare the structure-function relationship between peripapillary optical microangiography (OMAG) measurements and standard automated perimetry (SAP) loss by comparison with peripapillary retinal nerve fiber layer (pRNFL) thickness in primary open-angle glaucoma.

MATERIALS AND METHODS

One eye from each of 128 patients with early-to-severe glaucoma (including preperimetric glaucoma) and 23 normal participants underwent optic nerve head scanning of the radial peripapillary capillaries and pRNFL scans with OMAG centered on the optic disc and SAP (mean age: 67.8±12.0 y; SAP mean deviation: -5.84±6.6 dB). Regional relationships between VPD, FI, pRNFL thickness, and corresponding SAP sensitivity were compared using linear and fractional polynomial (FP) models.

RESULTS

Structure was significantly related to function for all but the nasal pRNFL thickness region. For VPD, the coefficient of determination (R2) using the FP model was significantly stronger than that of the linear model (FP: 0.25 to 0.67, linear: 0.19 to 0.61), while no difference was found for FI in any region (FP: 0.19 to 0.44, linear: 0.15 to 0.42). R2 for VPD was stronger than FI and pRNFL (FP: 0.11 to 0.52, linear: 0.01 to 0.44) in inferior and superior regions, while VPD and FI were not different in temporal and nasal regions.

CONCLUSIONS

VPD showed a stronger association with visual field loss than FI or retinal nerve fiber layer thickness except in the temporal region. The FI relationship was weak but more linear around the peripapillary region. The strength of the structure-function relationship may differ depending on the region of OMAG measurements.

Vascular biomarkers from optical coherence tomography angiography and glaucoma: where do we stand in 2021?

Biomarkers of ocular blood flow originating from a wide variety of imaging modalities have been associated with glaucoma onset and progression for many decades. Advancements in imaging platforms including optical coherence tomography angiography (OCTA) have provided the ability to quantify vascular changes in glaucoma patients, alongside traditional measures such as retinal nerve fibre layer thickness and optic nerve head structure. Current literature on vascular biomarkers, as measured by OCTA, indicates significant relationships between glaucoma and blood flow and capillary density in the retina and ONH. The data currently available, however, are highly diverse and lack robust longitudinal data on OCTA vascular outcomes and glaucoma progression. Herein we discuss and summarize the relevant current literature on OCTA vascular biomarkers and glaucoma reviewed through March 1, 2021. Associations between OCTA vascular biomarkers and clinical structural and functional glaucoma outcomes as well as differences between glaucoma patients and healthy controls are reviewed and summarized. The available data identify significantly decreased flow density, flow index and vessel density in the ONH, peripapillary vascular layer and macula of glaucoma patients compared with controls. Whole image vessel density is also significantly decreased in glaucoma patients compared with controls, and this outcome has been found to correspond to severity of visual field loss. OCTA vascular biomarkers alongside clinical structural outcomes may aid in assessing overall risk for glaucoma in patients.

Analysis of structural and vascular changes of the optic nerve head and macula in different stages of primary open angle glaucoma

Background/Aim. It is possible that patients with open-angle glaucoma be asymptomatic in the early stage of the disease. The aim of this study was to determine the structural and vascular changes of the optic disc (OD) and macula in healthy and primary open-angle glaucoma (POAG) eyes, detected by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) as well as the correlation of the OCT and OCTA measurements and their association with the presence of POAG. Methods. A total of 196 eyes were included and classified into four groups, out of them 48 were healthy eyes, 51 eyes were with mild POAG, 50 eyes with moderate POAG, and 47 eyes with advanced glaucoma. All subjects underwent standard ophthalmic examination. OCT measured the mean, superior and inferior retinal nerve fiber layer (RNFL) thickness and macular ganglion cell complex (GCC). OCTA evaluated the vessel capillary density (VCD) in OD, foveal avascular zone (FAZ) and macular vessel density (VD) in the superficial (SL) and deep (DL) retinal vascular plexus. Results. Patient characteristics were similar except for decreased visual acuity, thinner corneas, higher intraocular pressure and higher cup/disc ratio in POAG patients. OCT results showed that RNFL and GCC thickness gradually de-creased according to POAG severity. Within the assessment conducted by OCTA, VCD?s value in OD also diminished with the progression of POAG, having the lowest value in patients with advanced glaucoma. The same pattern was observed in vessel density around FAZ and VD values. Comparing the structural and vascular changes, a significant positive correlation was found between RNFL thickness and VCD inside OD, and GCC and VD SL in the macular zone. Conclusion. OCT and OCTA allow of a noninvasive quantification of the structural and vascular changes in OD and the macular zone and accurately distinguish between healthy eyes and eyes with POAG, showing an association with the presence and progression of glaucoma.

Optical Microangiography and Progressive Retinal Nerve Fiber Layer Loss in Primary Open Angle Glaucoma

PURPOSE

To evaluate the association between optical microangiography (OMAG) measurements and progressive retinal nerve fiber layer (RNFL) loss in primary open angle glaucoma (POAG).

DESIGN

Prospective case series.

METHODS

Sixty-four eyes of 40 patients with POAG (108 quadrants) with mild to moderate functional damage were longitudinally studied for at least 2 years and with a minimum of 3 optical coherence tomography examinations. OMAG imaging was performed at the baseline visit. Effect of clinical parameters (age, sex, presence of systemic diseases, central corneal thickness, presence of disc hemorrhage, and mean and fluctuation of intraocular pressure during follow-up), baseline hemifield mean deviation, baseline quadrant optical coherence tomography RNFL and ganglion cell inner plexiform layer thickness), and OMAG (peripapillary and macular perfusion density [PD] and vessel density [VD]) on the rate of RNFL change was evaluated using linear mixed models.

RESULTS

Average (±SD) mean deviation, RNFL, and ganglion cell inner plexiform layer thickness of the analyzed quadrants at baseline were -5.5 ± 2.9 dB, 96.5 ± 17.9 µm, and 73.8 ± 8.6 µm, respectively. Peripapillary PD and VD in the quadrant were 44.6% ± 5.9% and 17.5 ± 2.2 mm/mm², respectively. Rate of quadrant RNFL change was -1.8 ± 0.6 µm/y. Multivariate mixed models showed that lower peripapillary PD (coefficient = 0.08, P = .01) and lower VD (coefficient = 0.21, P = .02) were significantly associated with a faster rate of RNFL loss.

CONCLUSIONS

Lower baseline peripapillary PD and VD measured using OMAG were significantly associated with a faster rate of RNFL loss in POAG. OMAG imaging provides useful information about the risk of glaucoma progression and the rate of disease worsening.

Long-term repeatability of peripapillary optical coherence tomography angiography measurements in healthy eyes

This is a prospective observational study to establish the short- and long-term repeatability of measurements of peripapillary optical coherence tomography angiography (OCTA) parameters in healthy eyes and identify factors affecting long-term repeatability. We enrolled 84 healthy eyes. Participants with a history of any ophthalmic disease (except high myopia) or intraocular surgery were excluded from the study. An experienced examiner performed OCTA using disc-centered 6 × 6 mm scans. All examinations were conducted twice at 5-min intervals at the initial visit and repeated at least 6 months later. For short-term repeatability, the coefficient of variation (CV) was 2.94–4.22% and the intraclass correlation coefficient (ICC) was 0.840–0.934. For long-term repeatability, the CV was 2.73–3.84% and the ICC was 0.737–0.934. Multivariate analyses showed that the axial length (AL) (B = 0.970; p = 0.002) and mean signal strength (SS) (B = − 2.028; p < 0.001) significantly affected long-term repeatability. Measurements of peripapillary OCTA parameters exhibited excellent short-term and good long-term repeatability in healthy individuals. The mean SS and AL affected long-term repeatability and should be considered while interpreting peripapillary OCTA images.

Combining OCT and OCTA for Focal Structure-Function Modeling in Early Primary Open-Angle Glaucoma

Purpose

To investigate modeling of the focal visual field (VF) loss by combining structural measurements and vascular measurements in eyes with early primary open-angle glaucoma (POAG).

Methods

In this cross-sectional study, subjects with early glaucoma (VF mean deviation, ≥−6 dB) underwent optical coherence tomography (OCT) imaging, optical coherence tomography angiography (OCTA) imaging, and Humphrey 24-2 VF tests. Capillary perfusion densities (CPDs) were calculated after the removal of large vessels in the OCTA images. Focal associations between VF losses at the individual VF test locations, circumpapillary retinal nerve fiber layer (RNFL) thickness measurements from OCT, and CPDs were determined using nerve fiber trajectory tracings. Linear mixed models were used to model focal VF losses at each VF test location.

Results

Ninety-seven eyes with early POAG (VF mean deviation, −2.47 ± 1.64 dB) of 71 subjects were included. Focal VF modeling using a combined RNFL–CPD approach resulted in a median adjusted R² value of 0.30 (interquartile range [IQR], 0.13–0.55), whereas the RNFL-only and CPD-only approaches resulted in median values of 0.22 (IQR, 0.10–0.51) and 0.26 (IQR, 0.10–0.52), respectively. Seventeen VF locations with the combined approach had an adjusted R² value greater than 0.50. Likelihood testing at each VF test location showed that the combined approach performed significantly better at the superior nasal VF regions of the eyes compared with the univariate approaches.

Conclusions

Modeling of focal VF losses showed improvements when structural thickness and vascular parameters were included in tandem. Evaluation of VF defects in early glaucoma may benefit from considering both RNFL and OCTA characteristics.

Optic disc microvascularity in patients with intravitreal dexamethasone implantation for branch retinal vein occlusion

PURPOSE

To compare changes in optic disc microvascular parameters before and after treatment of patients who received IVD for macular edema secondary to BRVO, using optical coherence tomography angiography (OCT-A).

METHODS

Eighteen BRVO patients who received only IVD treatment and 20 healthy controls were retrospectively reviewed. Patients with moderate or severe IOP spikes (>6mmHg) after implantation were excluded from the study. Whole, peripapillary, inside disc capillary density and retinal nerve fiber layer thickness (RNFLT) were recorded at the 2nd and 6th months after implantation.

RESULTS

Whole, peripapillary and inside disc capillary densities were significantly lower in BRVO patients before implantation than in the control group (P<0.001 for all comparisons). Despite a mild mean IOP increase after IVD, no significant change was observed in whole, peripapillary and inside disc capillary vascular densities in the 2nd and 6th months (P>0.05 for all comparisons). The mean RNFLT of BRVO patients before IVD was lower than the control group, but this difference was not statistically significant (110.1±12.3μm and 115.6±10.7μm, P=0.131). The mean RNFLT at the 2nd and 6th months did not show a statistically significant difference after implantation (P=0.239, P=0.459).

CONCLUSIONS

OCT-A shows the decrease in whole, peripapillary and inside disc microvascular parameters in BRVO patients compared to healthy subjects. No significant change in optic nerve head microvascular parameters was observed in patients without moderate or severe IOP spikes after treatment with IVD.

Referenced scans improve the repeatability of optical coherence tomography angiography measurements in normal and glaucoma eyes

AIM

To compare the repeatability of peripapillary perfusion density and flux index measurements on referenced and non-referenced optical microangiography (OMAG) scans in normal, glaucoma suspect and glaucoma eyes.

METHODS

In a cross-sectional study, 48 eyes (33 subjects) underwent three repeat, non-referenced peripapillary OMAG scans in the same session and 43 eyes (25 subjects) underwent three referenced peripapillary OMAG scans. In the referenced scan group, repeat scans (second and the third scan) were acquired exactly on the baseline (first) scan using the 'track to prior scan' option on the device. Repeatability estimates of the mean and four-sector (temporal, superior, nasal and inferior) OMAG measurements on the non-referenced and referenced scans were assessed using within-subject coefficient of repeatability (CR_w) and variation (CV_w).

RESULTS

CR_w (%) of peripapillary perfusion density measurements (range: 2.0-4.1) on non-referenced scans were significantly higher than that on referenced scans (range: 1.4-2.7). CV_w (%) on non-referenced and referenced scans ranged from 1.7 to 3.1 and from 1.2 to 2.1, respectively . CR_w of flux index on non-referenced and referenced scans ranged from 4.4 to 5.8 and from 3.6 to 4.8, respectively. CV_w on non-referenced and referenced scans ranged from 4.1 to 5.2 and from 3.3 to 4.5, respectively.

CONCLUSIONS

Repeatability estimates of OMAG measurements were better on referenced scans compared with non-referenced scans. Perfusion density measurements had lower variability than flux index. OCTA-measured perfusion density of referenced scans is preferable for monitoring vascular change in glaucoma.

Analysis of Retinal Capillary Using Optical Coherence Tomographic Angiography of Unilateral Normal Tension Glaucoma

Purpose: The purpose of this study was to analyze retinal capillary parameters using optical coherence tomography angiography (OCTA) of the affected eye and the fellow eye of unilateral normal tension glaucoma (NTG) patients and compare the findings with eyes from a normal control group.Methods: A retrospective cross-sectional study was carried out on patients diagnosed with unilateral NTG (24 affected eyes and 24 fellow eyes each) and normal individuals (29 eyes, the control group). OCTA was used to measure the vascular density (VD) and perfusion density (PD) of the macular area and the peripapillary area.Results: In the superficial capillary plexus, the fellow eye group of unilateral NTG patients showed a decrease in VD of the inner-inferior and PD of the inner-inferior and outer-average peripapillary area, compared with the normal control group (p = 0.008, p < 0.001, and p = 0.001). In the affected NTG eye group, the VD (p = 0.014, p = 0.011, p < 0.001, p < 0.001, and p < 0.001) and PD (p = 0.017, p = 0.023, p < 0.001, p = 0.001, and p < 0.001) of the total, inner-average, inner-inferior, and outer-inferior peripapillary area, and the outer-inferior macular area decreased compared to the fellow eye and normal control group, as well as the VD of the outer-average peripapillary area (p = 0.010). The PD of the outer-average peripapillary area (p = 0.003); the VD (p = 0.041, p = 0.008, p = 0.006) and the PD (p = 0.013, p < 0.001, p = 0.001) of the total, inner-inferior, and outer-average macular area; and the PD of the outer-temporal macular area (p = 0.003) were lower than the normal control group. There was no difference in the VD or PD obtained from the deep capillary plexus of the macular area among the groups.Conclusions: It is useful to observe retinal capillary parameters using OCTA for patients with unilateral NTG.

Measurements of OCT Angiography Complement OCT for Diagnosing Early Primary Open-Angle Glaucoma

PURPOSE

To compare measurements of global and regional circumpapillary capillary density (cpCD) with retinal nerve fiber layer (RNFL) thickness and characterize their relationship with visual function in early primary open-angle glaucoma (POAG).

DESIGN

Cross-sectional study.

PARTICIPANTS

Eighty healthy eyes, 64 preperimetric eyes, and 184 mild POAG eyes from the Diagnostic Innovations in Glaucoma Study.

METHODS

Global and regional RNFL thickness and cpCD measurements were obtained using OCT and OCT angiography (OCTA). For direct comparison at the individual and diagnostic group level, RNFL thickness and capillary density values were converted to a normalized relative loss scale.

MAIN OUTCOME MEASURES

Retinal nerve fiber layer thickness and cpCD normalized loss at the individual level and diagnostic group. Global and regional areas under the receiver operating characteristic curve (AUROC) for RNFL thickness and cpCD to detect preperimetric glaucoma and glaucoma, R² for the strength of associations between RNFL thickness function and capillary density function in diagnostic groups.

RESULTS

Both global and regional RNFL thickness and cpCD decreased progressively with increasing glaucoma severity (P < 0.05, except for temporal RNFL thickness). Global and regional cpCD relative loss values were higher than those of RNFL thickness (P < 0.05) in preperimetric glaucoma (except for the superonasal region) and glaucoma (except for the inferonasal and superonasal regions) eyes. Race, intraocular pressure (IOP), and cpCD were associated with greater cpCD than RNFL thickness loss in early glaucoma at the individual level (P < 0.05). Global measurements of capillary density (whole image capillary density and cpCD) had higher diagnostic accuracies than RNFL thickness in detecting preperimetric glaucoma and glaucoma (P < 0.05; except for cpCD/RNFL thickness comparison in glaucoma [P = 0.059]). Visual function was significantly associated with RNFL thickness and cpCD globally and in all regions (P < 0.05, except for temporal RNFL thickness-function association [P = 0.070]).

CONCLUSIONS

Associations between capillary density and visual function were found in the regions known to be at highest risk for damage in preperimetric glaucoma eyes and all regions of mild glaucoma eyes. In early glaucoma, capillary density loss was more pronounced than RNFL thickness loss. Individual characteristics influence the relative magnitudes of capillary density loss compared with RNFL thickness loss. Retinal nerve fiber layer thickness and microvascular assessments are complementary and yield valuable information for the detection of early damages seen in POAG.

Optical Coherence Tomography and Glaucoma

Early detection and monitoring are critical to the diagnosis and management of glaucoma, a progressive optic neuropathy that causes irreversible blindness. Optical coherence tomography (OCT) has become a commonly utilized imaging modality that aids in the detection and monitoring of structural glaucomatous damage. Since its inception in 1991, OCT has progressed through multiple iterations, from time-domain OCT, to spectral-domain OCT, to swept-source OCT, all of which have progressively improved the resolution and speed of scans. Even newer technological advancements and OCT applications, such as adaptive optics, visible-light OCT, and OCT-angiography, have enriched the use of OCT in the evaluation of glaucoma. This article reviews current commercial and state-of-the-art OCT technologies and analytic techniques in the context of their utility for glaucoma diagnosis and management, as well as promising future directions.

Optical coherence tomographic angiography study of perfusion recovery after surgical lowering of intraocular pressure

We investigated the time and location of retinal perfusion recovery after surgical intraocular pressure (IOP) lowering in glaucoma by using optical coherent tomography angiography (OCTA). Seventeen patients were analyzed. The 4.5 × 4.5-mm OCTA scans centered on the disc were performed preoperatively and postoperatively at 6 weeks, 3 months, and 6 months. The peripapillary retinal nerve fiber layer (NFL) thickness, NFL plexus capillary density (NFLP-CD) and visual field (VF) were measured overall and in 8 corresponding sectors. The low-perfusion area (LPA) was used to assess the cumulative area where local NFLP-CD was significantly below normal. At 6 months, the average IOP decreased 5.3 mmHg (P = 0.004), LPA decreased by 15% (P = 0.005), and NFLP-CD improved by 12% (P < 0.001). The NFL thickness and VF mean deviation didn’t change significantly at any time point. Among the sectors with significant preoperative NFLP-CD loss, the recovery at 6 months was greatest in sectors with minimal preoperative NFL thinning (P < 0.001). In conclusion, surgical IOP lowering may improve NFLP capillary perfusion after 6 months. The perfusion recovery tended to occur in areas with minimal NFL thinning at baseline. OCTA parameters may have potential usefulness as pharmacodynamic biomarkers for glaucoma therapy.

Sectorwise analysis of peripapillary vessel density and retinal nerve fiber layer thickness in exfoliation syndrome

PURPOSE

This cross-sectional study compared the peripapillary vessel density and retinal nerve fiber layer (RNFL) thickness in patients with exfoliation syndrome (XFS) and healthy controls for evaluation of the early structural and vascular alterations in XFS.

METHODS

One eye was included from 75 patients with XFS and 54 healthy controls. The patients with XFS were matched the controls for age, intraocular pressure and axial length. The vascular density of the radial peripapillary capillaries (RPCs) and the peripapillary RNFL thickness were evaluated with optical coherence tomography angiography.

RESULTS

The mean peripapillary RNFL thicknesses of the groups were similar in all sectors (p > 0.05 for all). However, eyes with XFS demonstrated lower mean peripapillary vessel densities in all areas (p < 0.05 for all) except for the nasal sector (p = 0.68) compared to the controls. The gradual age correlated decline in the peripapillary RNFL thickness and the RPC vessel density observed in the healthy eyes was absent in XFS (r = - 0.14 p = 0.65 and r = - 0.23 p = 0.05).

CONCLUSIONS

Alterations in the peripapillary vascular density despite a preserved RNFL thickness in XFS supports the hypothesis that vascular alterations may precede structural alterations and have an important role in the pathogenesis of XFS. XFS may have different effects on the microvasculature of different peripapillary areas, with the nasal sector being mostly preserved.

Relationship between peripapillary vessel density and visual function based on Garway-Heath sectorization in open-angle glaucoma

Purpose:

To investigate the relationship between peripapillary vessel density (pVD) and visual field sensitivity (VFS) and between peripapillary retinal nerve fiber layer thickness (pRNFLT) and VFS, based on Garway-Heath sectorization in open-angle glaucoma patients.

Methods:

Sixty-six eyes of healthy subjects and 84 eyes of glaucoma subjects were included. All subjects underwent several eye examinations, including standard automated perimetry and optical coherence tomography angiography. Sectoral structure-function relationships based on the Garway-Heath sectorization were compared among normal subjects, the ‘mild glaucoma,’ and ‘moderate-to-severe glaucoma’ group. Multivariate analyses were performed for each sector to determine the factors related to VFS. The diagnostic abilities of vessel density parameters and RNFLT were evaluated by calculating the area under the receiver operating characteristic curves (AUROC).

Results:

The correlation between pVD-VFS and pRNFLT-VFS was statistically significant in the glaucoma group independent of the VFS sector. In the glaucoma group, VFS in the temportal sector was statistically related in a multivariate model to pVD, pRNFLT and age (R² = 0.721; P = 0.007, < 0.001, .15, respectively). We found pRNFLT and age were significantly associated with VFS in glaucoma. The AUROC values of pVD in the inferotemporal sector of the total, mild, and moderate-to-severe glaucoma (0.843, 0.714, and 0.972, respectively) were comparable to pRNFLT in this sector (0.833, 0.718, 0.948, respectively).

Conclusion:

Since the relationship between pVD and VFS in the papillomacular area was significant, measuring pVD and RNFLT in the corresponding area will be valuable in expanding our pathophysiologic knowledge of the paracentral field defects in glaucoma.

The Macular Choriocapillaris Flow in Glaucoma and Within-Day Fluctuations: An Optical Coherence Tomography Angiography Study

Purpose

To assess quantitatively the choriocapillaris (CC) perfusion area in the macular area of healthy eyes, eyes with primary open-angle glaucoma, and eyes with ocular hypertension using optical coherence tomography angiography (OCTA).

Methods

A consecutive series of healthy individuals and patients with glaucoma and ocular hypertension were recruited prospectively in this single-center, cross-sectional study based in Milan, Italy. OCTA was performed in the morning and evening, along with a complete ophthalmologic examination. Macular superficial capillary plexus vessel density (SCP-VD) and the thicknesses of the retina and ganglion cell complex (GCC), as well as their fluctuations, were investigated.

Results

Thirty-nine eyes from 24 individuals with glaucoma (mean age = 58.79 ± 6 years), 43 eyes from 27 individuals with ocular hypertension (59.19 ± 6 years), and 54 eyes from 35 controls (58.27 ± 6 years) were enrolled. The mean CC perfusion area values were not significantly different among the three groups in the morning or evening (P ≥ 0.47). In contrast, SCP-VD, retinal thickness, and GCC thickness were statistically different among the groups (P ≤ 0.016), except for the foveal SCP-VD (P ≥ 0.19) and the evening foveal thickness (P = 0.57). Diurnal changes in the CC perfusion area, SCP-VD, retinal thickness, and GCC thickness were not statistically significant (P ≥ 0.16). Systemic hypertension, sex, age, axial length, and diurnal changes in intraocular pressure were not significantly associated with morning or evening measurements, or with diurnal fluctuations (P ≥ 0.07).

Conclusions

The macular CC flow perfusion area appears unaffected in eyes with primary open-angle glaucoma. No significant diurnal changes were observed in any of the parameters investigated.

The role of pattern electroretinograms and optical coherence tomography angiography in the diagnosis of normal-tension glaucoma

In this study, we investigated the correlation between pattern electroretinogram (PERG) and optical coherence tomography angiography (OCTA) parameters for diagnosis in patients with normal-tension glaucoma (NTG). Forty-nine normal individuals (49 eyes) and 60 patients with NTG (60 eyes) were enrolled. OCTA and PERG parameters, such as macular vessel density (VD) and the amplitude of N35–P50 and P50–N95, were measured. Correlation analyses were performed between the parameters, and the area under the curve (AUC) was used to identify their diagnostic ability for NTG. Macular VD and the amplitude of N35–P50 and P50–N95 showed significant differences between the normal individuals and patients with NTG. Correlation between P50 and N95 amplitude and macular VD was significant in the normal and early glaucoma groups. Macular VD showed a higher AUC value (0.730) than that of P50–N95 amplitude (0.645) in the early glaucoma group. In the moderate to severe glaucoma group, the AUC value of the amplitude of P50–N95 (0.907) was higher than that of macular VD (0.876). The results indicate that PERG and OCTA parameters may identify glaucoma in its early stage, based on the severity of glaucomatous damage in patients with NTG.

Segregation of neuronal-vascular components in a retinal nerve fiber layer for thickness measurement using OCT and OCT angiography

Assessment of the circumpapillary retinal nerve fiber layer (RNFL) provides crucial knowledge on the status of the optic nerve. Current circumpapillary RNFL measurements consider only thickness, but an accurate evaluation should also consider blood vessel contribution. Previous studies considered the presence of major vessels in RNFL thickness measurements from optical coherence tomography (OCT). However, such quantitative measurements do not account for smaller vessels, which could also affect circumpapillary RNFL measurements. We present an approach to automatically segregate the neuronal and vascular components in circumpapillary RNFL by combining vascular information from OCT angiography (OCTA) and structural data from OCT. Automated segmentation of the circumpapillary RNFL using a state-of-the-art deep learning network is first performed and followed by the lateral and depth-resolved localization of the vascular component by vertically projecting the vessels along the circular scan from OCTA vessels map onto the segmented RNFL. Using this proposed approach, we compare the correlations of circumpapillary RNFL thicknesses with age at different levels of vessel exclusion (exclusion of major vessels only vs both major- and micro-vessels) and also evaluate the thickness variability in 75 healthy eyes. Our results show that the ratio of major- and micro-vessels to circumpapillary RNFL achieved a stronger correlation with aging (r = 0.478, P < .001) than the ratio with only major vessels to circumpapillary RNFL (r = 0.027, P = .820). Exclusion of blood vessels from circumpapillary RNFL thickness using OCTA imaging provides a better measure of the neuronal components and could potentially improve the diagnostic performance for disease detection.

[Optical coherence tomography angiography (OCT-A) : Overview of the technique and the possible clinical and scientific applications]

Optical coherence tomography angiography (OCT-A) is a very promising noninvasive imaging modality. For the first time it enables a precise 3‑dimensional depiction of the retinal microcirculation without the use of contrast medium and can be carried out rapidly and simply. This makes OCT‑A interesting for both scientific and clinical applications. In many ophthalmological diseases, such as glaucoma and diabetic retinopathy, OCT‑A can detect vascular alterations even in the early stages of the disease. These alterations partially correlate with functional parameters. The use of OCT‑A in the clinical routine is currently still limited due to imaging artifacts, high acquisition costs and large amounts of data; however, the scientific interest in this new technology is enormous and from our point of view it will become established in the clinical routine in the future.

Advances in translational imaging of the microcirculation

The past few decades have seen an explosion in the development and use of methods for imaging the human microcirculation during health and disease. The confluence of innovative imaging technologies, affordable computing power, and economies of scale have ushered in a new era of "translational" imaging that permit us to peer into blood vessels of various organs in the human body. These imaging techniques include near-infrared spectroscopy (NIRS), positron emission tomography (PET), and magnetic resonance imaging (MRI) that are sensitive to microvascular-derived signals, as well as computed tomography (CT), optical imaging, and ultrasound (US) imaging that are capable of directly acquiring images at, or close to microvascular spatial resolution. Collectively, these imaging modalities enable us to characterize the morphological and functional changes in a tissue's microcirculation that are known to accompany the initiation and progression of numerous pathologies. Although there have been significant advances for imaging the microcirculation in preclinical models, this review focuses on developments in the assessment of the microcirculation in patients with optical imaging, NIRS, PET, US, MRI, and CT, to name a few. The goal of this review is to serve as a springboard for exploring the burgeoning role of translational imaging technologies for interrogating the structural and functional status of the microcirculation in humans, and highlight the breadth of current clinical applications. Making the human microcirculation "visible" in vivo to clinicians and researchers alike will facilitate bench-to-bedside discoveries and enhance the diagnosis and management of disease.

Progression of Macular Vessel Density in Primary Open-Angle Glaucoma: A Longitudinal Study

PURPOSE

To evaluate the rate of progression of macular vessel density (mVD) in primary open-angle glaucoma (POAG) and explore the relationship between the progression of mVD and macular ganglion cell-inner plexiform layer (mGCIPL) thickness and parapapillary retinal nerve fiber layer (pRNFL) thickness.

DESIGN

Prospective cohort study.

METHODS

In this study, 102 eyes with POAG were followed for 36.6 ± 6.4 months. The rates of progression were estimated by linear models. The agreement of progression detection among the 3 parameters was evaluated with Kappa statistics. The influence of baseline measurements on the rates of progression of mGCIPL thickness, pRNFL thickness, and mVD was investigated by linear mixed modeling. Kaplan-Meier survival analysis was adopted to calculate the survival probabilities.

RESULTS

The respective rate of progression by linear regression was -0.102 ± 0.054 μm/month, -0.160 ± 0.086 μm/month, and -0.199 ± 0.073 %/month for mGCIPL thickness, pRNFL thickness, and mVD. The agreement in detection of progression among them was poor with the Conger's Kappa coefficient of 0.098 (95% confidence interval: -0.025~0.220, P = .116). The significant factors influencing the rate of progression of mVD were baseline mGCIPL thickness, baseline pRNFL thickness, and baseline mVD (P ≤ .001), while baseline mVD was not a significant factor influencing the rates of progression of mGCIPL thickness and pRNFL thickness (P ≥ .659). Also, pRNFL thickness had a better survival probability compared with the other 2 parameters (P = .025).

CONCLUSIONS

The mGCIPL thickness, pRNFL thickness, and mVD decreased over time in POAG eyes. The rate of reduction of mVD was significantly influenced by the baseline measurements of mGCIPL thickness, pRNFL thickness, and mVD.

OCT Angiography for the Diagnosis of Glaucoma: A Report by the American Academy of Ophthalmology

PURPOSE

To review the current published literature on the use of OCT angiography (OCTA) to help detect changes associated with the diagnosis of primary open-angle glaucoma.

METHODS

Searches of the peer-reviewed literature were conducted in March 2018, June 2018, April 2019, December 2019, and June 2020 in the PubMed and Cochrane Library databases. Abstracts of 459 articles were examined to exclude reviews and non-English articles. After inclusion and exclusion criteria were applied, 75 articles were selected and the panel methodologist rated them for strength of evidence. Three articles were rated level I and 57 articles were rated level II. The 15 level III articles were excluded.

RESULTS

OCT angiography can detect decreased capillary vessel density within the peripapillary nerve fiber layer (level II) and macula (level I and II) in patients with suspected glaucoma, preperimetric glaucoma, and perimetric glaucoma. The degree of vessel density loss correlates significantly with glaucoma severity both overall and topographically (level II) as well as longitudinally (level I). For differentiating glaucomatous from healthy eyes, some studies found that peripapillary and macular vessel density measurements by OCTA show a diagnostic ability (area under the receiver operating characteristic curve) that is comparable with structural OCT retinal nerve fiber and ganglion cell thickness measurements, whereas other studies found that structural OCT measurements perform better. Choroidal or deep-layer microvasculature dropout as measured by OCTA is also associated with glaucoma damage (level I and II). Lower peripapillary and macular vessel density and choroidal microvasculature dropout are associated with faster rates of disease progression (level I and II).

CONCLUSIONS

Vessel density loss associated with glaucoma can be detected by OCTA. Peripapillary, macular, and choroidal vessel density parameters may complement visual field and structural OCT measurements in the diagnosis of glaucoma.

Differences in cerebral blood vasculature and flow in awake and anesthetized mouse cortex revealed by quantitative optical coherence tomography angiography

BACKGROUND

Most of the in vivo neurovascular imaging studies are performed in anesthetized animals. However, anesthesia significantly affects cerebral hemodynamics.

NEW METHOD

We applied optical coherence tomography (OCT) methods such as optical microangiography (OMAG) and Doppler optical microangiography (DOMAG) to quantitatively evaluate the effect of anesthesia in cerebral vasculature and blood flow in mouse brain.

RESULTS

The OMAG results indicated the increase of large vessel diameter and capillary density induced by ketamine-xylazine and isoflurane, meaning that both anesthetics caused vasodilation. In addition, the preliminary results from DOMAG showed that isoflurane increased the baseline cerebral blood flow.

COMPARISON WITH EXISTING METHODS

In comparison with other in vivo imaging modalities, OCT can provide label-free assessment of cortical tissue including tissue morphology, cerebral blood vessel network and flow information down to capillary level, with a large field of view and high imaging speed.

CONCLUSIONS

OCT angiography methods demonstrated the ability to measure the differences in the baseline morphological and flow parameters of both large and capillary cerebrovascular networks between awake and anesthetized mice.

Comparison of subfoveal choroidal thickness and retinal nerve fiber layer thickness in patients with coronary slow flow phenomenon and microvascular angina: Optical coherence tomography based study

BACKGROUND

The aim of this study was to evaluate and compare the subfoveal choroidal thickness (SFCT) and peripapillary retinal nerve fiber layer thickness (pRNFLT) in patients with microvascular angina (MA), coronary slow flow phenomenon (CSFP) and healthy controls.

METHODS

Thirty-two consecutive patients with MA, 35 consecutive patients with CSFP and 40 age and sex-matched controls were enrolled. SFCT, average pRNFLT and four quadrants of pRNFLT were measured by spectral domain- optical coherence tomography (SD-OCT).

RESULTS

The mean SCFT in patients with CSFP (267.57 ± 30.61 μm) was significantly thinner than those of patients with MA (288.84 ± 28.25 μm) and control (291.21 ± 31.75 μm) (p = 0.002) while SFCT of patients with MA were similar with those of controls. Patients with CSFP had thinner superior and inferior pRNFLT compared to patients with MA and controls (p < 0.001 and p = 0.005, respectively) while there were no significant differences in average pRNFLT, nasal and temporal quadrant of pRNFLTs among three groups. In the multivariate linear regression analyses, the presence of CSFP was found negatively correlated with SFCT and superior pRNFLT.

CONCLUSION

Patients with CSFP had thinner SFCT, superior and inferior quadrants of pRNFLT proposing the presence of a generalized endothelial dysfunction and increased microvascular resistance in these patients.

Diurnal Measurements of Macular Thickness and Vessel Density on OCT Angiography in Healthy Eyes and Those With Ocular Hypertension and Glaucoma

PRECIS

Macular superficial capillary plexus (SCP) and thickness are reduced in eyes with glaucoma and ocular hypertension, but do not change significantly during the day. No relationships with age, intraocular pressure, systemic hypertension, or axial length were found.

PURPOSE

The purpose of this study was to evaluate diurnal differences in retinal thickness and vessel density (VD) of the macular SCP and deep capillary plexus (DCP) using optical coherence tomography angiography among 3 groups: eyes with glaucoma, eyes with ocular hypertension, and healthy eyes.

METHODS

A consecutive series of individuals was recruited prospectively. Optical coherence tomography angiography was performed in the morning and in the evening.

RESULTS

Forty eyes from 23 individuals with glaucoma (58.35±6 y), 52 eyes from 32 individuals with ocular hypertension (58.84±7 y), and 73 eyes from 44 controls (57.84±6 y) were enrolled. Morning and evening measurements of all SCP-VD and retinal thickness parameters were statistically significantly different (P<0.04) among the 3 groups of eyes. None of the DCP-VD parameters were significantly different. Daily changes in SCP-VD, DCP-VD, and retinal thickness among the groups of eyes were not statistically significant. Systemic hypertension, age, axial length, and diurnal changes in intraocular pressure were not significantly associated with diurnal fluctuations of SCP-VD, DCP-VD, or retinal thickness (P>0.19). A positive linear correlation in diurnal changes was found between SCP-VD and DCP-VD in the fovea and in the parafovea (r=0.5567 and 0.5892, respectively) and between SCP-VD and retinal thickness in the fovea and in the parafovea (r=-0.2288 and 0.2418, respectively).

CONCLUSIONS

Macular SCP-VD and thickness are reduced in eyes with glaucoma and ocular hypertension. Although diurnal changes in SCP-VD, DCP-VD and macular thickness were not significant among the groups, some linear correlations in increasing or decreasing values of the investigated parameters were found.

Peripapillary and Macular Microcirculation in Glaucoma Patients of African and European Descent Using Optical Coherence Tomography Angiography

PRéCIS:: We found no significant differences in peripapillary and macula microcirculation blood flow metrics in eyes with open-angle glaucoma of African descent (AD) and European descent (ED) as detected by optical coherence tomography angiography (OCTA).

PURPOSE

The purpose of this study was to investigate the peripapillary retinal nerve fiber layer (RNFL) and macular vascular microcirculation in subjects of AD and ED with open-angle glaucoma using OCTA.

PATIENTS AND METHODS

One eye from each subject was scanned using AngioPlex OCTA system covering both a 6×6 mm scanning area centered at the optic nerve head and at the foveola. Peripapillary RNFL and macular microcirculation were measured by calculating the overall flux and vessel area density excluding the large retinal vessels. Two-sample, independent t tests were used to compare the OCTA metrics between AD and ED eyes. Linear regression models were used to investigate the correlation between OCTA metrics and structural and functional parameters.

RESULTS

Twenty-eight eyes of AD and 56 eyes of ED were included in the study. There was no significant difference in age, sex, hypertension, antihypertensive medications, diabetes, systolic and diastolic blood pressure, mean ocular perfusion pressure, RNFL thickness and visual field (VF) mean deviation and VF pattern standard deviation (P≥0.054) between AD and ED eyes included. Both groups had similar OCTA blood flow metrics (P≥0.161). OCTA blood flow metrics were significantly correlated with VF mean deviation (r≥0.466), VF pattern standard deviation (r≤-0.366) and RNFL thickness (r≥0.333).

CONCLUSIONS

No significant differences were found in peripapillary and macular microcirculation detected by OCTA between AD and ED glaucomatous eyes. Peripapillary and macular microcirculation were significantly correlated with disease severity in AD and ED glaucomatous eyes.

Peripapillary Perfused Capillary Density in Acute Angle-Closure Glaucoma: An Optical Coherence Tomography Angiography Study

PURPOSE

To compare peripapillary perfused capillary density (PCD) on optical coherence tomography angiography among resolved acute angle-closure (AAC), primary open-angle glaucoma (POAG), and control eyes.

DESIGN

Prospective, cross-sectional, observational study.

METHODS

All patients with resolved AAC or POAG of varying severity and controls were enrolled. We obtained 4.5 × 4.5 mm2 optical coherence tomography angiography images of the optic nerve head. PCD was analyzed using customized software with major vessel removal. Continuous variables were assessed using the analysis of variance and Bonferroni correction test. A marginal model of generalized estimating equations was used to adjust for confounding factors and interocular correlation.

RESULTS

The study included 44 eyes with resolved AAC (mean duration of elevated intraocular pressure, 8.1 ± 10.9 days), 69 eyes with POAG, and 49 control eyes. PCD showed a similar decrease between AAC and POAG eyes (P > 0.99). After adjusting for age and sex, the mean difference in global PCD between each of the POAG stage groups and the AAC group was the highest in the severe POAG group (-3.43; 95% confidence interval [CI], -11.38 to 2.52; P = 0.211), followed by the mild POAG (0.68; 95% CI, -3.26 to 4.62; P = 0.735) and moderate POAG (0.20; 95% CI, -5.21 to 5.61; P = 0.942) groups. The duration of increased intraocular pressure did not affect PCD (P = 0.258 and 0.168 for global and annular PCDs, respectively).

CONCLUSIONS

The degree of microvascular attenuation in AAC eyes was not different from that in POAG eyes.

Plexus-specific retinal vascular anatomy and pathologies as seen by projection-resolved optical coherence tomographic angiography

Optical coherence tomographic angiography (OCTA) is a novel technology capable of imaging retinal vasculature three-dimensionally at capillary scale without the need to inject any extrinsic dye contrast. However, projection artifacts cause superficial retinal vascular patterns to be duplicated in deeper layers, thus interfering with the clean visualization of some retinal plexuses and vascular pathologies. Projection-resolved OCTA (PR-OCTA) uses post-processing algorithms to reduce projection artifacts. With PR-OCTA, it is now possible to resolve up to 4 distinct retinal vascular plexuses in the living human eye. The technology also allows us to detect and distinguish between various retinal and optic nerve diseases. For example, optic nerve diseases such as glaucoma primarily reduces the capillary density in the superficial vascular complex, which comprises the nerve fiber layer plexus and the ganglion cell layer plexus. Outer retinal diseases such as retinitis pigmentosa primarily reduce the capillary density in the deep vascular complex, which comprises the intermediate capillary plexus and the deep capillary plexus. Retinal vascular diseases such as diabetic retinopathy and vein occlusion affect all plexuses, but with different patterns of capillary loss and vascular malformations. PR-OCTA is also useful in distinguishing various types of choroidal neovascularization and monitoring their response to anti-angiogenic medications. In retinal angiomatous proliferation and macular telangiectasia type 2, PR-OCTA can trace the pathologic vascular extension into deeper layers as the disease progress through stages. Plexus-specific visualization and measurement of retinal vascular changes are improving our ability to diagnose, stage, monitor, and assess treatment response in a wide variety of optic nerve and retinal diseases. These applications will be further enhanced with the continuing improvement of the speed and resolution of the OCT platforms, as well as the development of software algorithms to reduce artifacts, improve image quality, and make quantitative measurements.

Longitudinal changes in superficial microvasculature in glaucomatous retinal nerve fiber layer defects after disc hemorrhage

Glaucoma is a multifactorial optic neuropathy, possibly involving vascular dysfunction, leading to the death of retinal ganglion cells and their axons. Disc hemorrhage (DH) is known to be closely associated with the widening of retinal nerve fiber layer defect (NFLD); however, it has not been well elucidated how DH affects retinal microvasculature. We aimed to investigate the association between DH history and longitudinal changes in superficial retinal microvasculature in NFLD. We enrolled 15 glaucoma patients with DH history (32 glaucomatous NFLD locations, with or without DH history). NFLD-angle, superficial retinal vessel density (VD), and decreased superficial retinal microvasculature (deMv)-angle were assessed using optical coherence tomography angiography for at least three times over time. The mean follow-up period and OCT/OCTA scan interval were 21.3 ± 5.4 months (range, 12–28) and 6.8 ± 0.4 months (range, 2–18), respectively. Linear mixed-effects models showed that the presence of DH history was significantly associated with an additional NFLD-angle widening of 2.19 degree/year (P = 0.030), VD decrease of 1.88%/year (P = 0.015), and deMv-angle widening of 3.78 degree/year (P < 0.001). These changes were significantly correlated with each other (P < 0.001). Thus, the widening of NFLD was closely associated with deMv, and DH was associated with a subsequent decrease in superficial retinal microvasculature in NFLD.

Quantitative Handheld Swept-Source Optical Coherence Tomography Angiography in Awake Preterm and Full-Term Infants

Purpose

To compare retinal vascular parameters acquired by handheld swept-source optical coherence tomography angiography (SS-OCTA) between nonsedated preterm and full-term infants.

Methods

Preterm and full-term infants at the University of Washington Medical Center were enrolled. Retinal angiograms (nominal size ∼7 × 7 mm²) were obtained at each routine retinopathy of prematurity (ROP) screening session for preterms and once during the first 72 hours of life for full-terms. Macular vessel area density and nonperfusion area were evaluated on the binarized vasculature map in both small (1.5 × 1.5 mm) and large (3 × 3 mm) quadrants. Average vessel diameter and tortuosity values were obtained from each large vessel branch (length >200 µm). All vascular analyses used previously published algorithms.

Results

Handheld SS-OCTA captured 31 of 55 (56%) high-quality volumes on 8 awake preterm infants (gestational age 28 ± 4 weeks, birth weight 891 ± 314 g, postmenstrual age at first imaging session 37 ± 2 weeks) and 48 of 54 (89%) volumes on 12 awake full-term infants (gestational age 39 ± 1 weeks, birth weight 3405 ± 329 g). Signal-to-noise ratio was 5.08 ± 1.52 dB in preterm and 4.90 ± 1.12 dB in full-term infants. Preterm infants had higher mean large vessel tortuosity compared to full-term infants (P = 0.004). The large nasal quadrant vessel area density of infants with stage 3 and/or pre-plus or worse ROP was higher than other preterm infants (P = 0.007).

Conclusions

Although inadequate image quality limited usable imaging sessions, handheld SS-OCTA achieved adequate signal-to-noise ratio in nonsedated infants for quantitative retinal vascular parameter analysis.

Translational Relevance

Large- and small-vessel parameters were associated with prematurity and ROP severity, respectively.

Focal Structure-Function Relationships in Primary Open-Angle Glaucoma Using OCT and OCT-A Measurements

Purpose

To evaluate the focal structure-function associations among visual field (VF) loss, optical coherence tomography angiography (OCT-A) vascular measurements, and optical coherence tomography (OCT) structural measurements in glaucoma.

Methods

In this cross-sectional study, subjects underwent standard automated perimetry, OCT-based nerve fiber thickness measurements, and OCT-A imaging. Mappings of focal VF test locations with OCT and OCT-A measurements were defined using anatomically adjusted nerve fiber trajectories and were studied using multivariate mixed-effects analysis. Segmented regression analysis was used to determine the presence of breakpoints in the structure-function associations.

Results

The study included 119 eyes from 86 Chinese subjects with primary open-angle glaucoma (POAG). VF mean deviation was significantly associated with global capillary perfusion density (β = 0.13 ± 0.08) and global retinal nerve fiber layer thickness (β = 0.09 ± 0.02). Focal capillary density (FCD) was significantly associated with VF losses at 34 VF test locations (66.7% of 24-2 VF), with 24 of the 34 locations being within 20° of retinal eccentricity. Focal nerve layer (FNL) thickness was significantly associated with 16 VF test locations (31.4% of 24-2 VF; eight locations within 20° eccentricity). For VF test locations in the central 10° VF, VF losses below the breakpoint were significantly associated with FCD (slope, 0.89 ± 0.12, P < 0.001), but not with FNL thickness (slope, 0.57 ± 0.39, P = 0.15).

Conclusions

Focal capillary densities were significantly associated with a wider range of visual field losses and in a larger proportion of the visual field compared to nerve fiber thickness.

Comparison of two different optical coherence tomography angiography devices in detecting healthy versus glaucomatous eyes - an observational cross-sectional study

Background

To understand the differences between two different optical coherence tomography angiography (OCTA) devices in detecting glaucomatous from healthy eyes by comparing their vascular parameters, diagnostic accuracy and test-retest reliability.

Methods

A cross-sectional observational study was performed on healthy and glaucoma subjects, on whom two sets of OCTA images of optic disc and macula were acquired using both AngioVue (Optovue, USA) and Swept Source (Topcon, Japan) OCTA devices during one visit. A novel in-house software was used to calculate the vessel densities. Diagnostic accuracy of the machines in differentiating healthy versus glaucomatous eyes was determined using area under the receiver operating characteristic curve (AUROC) and test-retest repeatability of the machines was also evaluated.

Results

A total of 80 healthy and 38 glaucomatous eyes were evaluated. Glaucomatous eyes had reduced mean vessel density compared to healthy controls in all segmented layers of the optic disc and macula using AngioVue (p ≤ 0.001). However, glaucomatous eyes had higher mean vessel density on optic disc scans using Swept Source, with lack of statistically significant difference between healthy and glaucomatous eyes. The AUROC showed better diagnostic accuracy of AngioVue (0.761–1.000) compared to Swept Source (0.113–0.644). The test-retest reliability indices were generally better using AngioVue than Swept Source.

Conclusions

AngioVue showed better diagnostic capability and test-retest reliability compared to Swept Source. Further studies need to be undertaken to evaluate if there is any significant difference between the various machines in diagnosing and monitoring glaucoma.

Macular microvascular parameters in the ganglion cell-inner plexiform layer derived by optical coherence tomography angiography: Vascular structure-central visual function analysis

PURPOSE

To investigate the relationships between global and sectoral macular vascular microcirculation parameters in the ganglion cell-inner plexiform layer (GCIPL) assessed by optical coherence tomography angiography (OCTA), and global and sectoral visual field (VF) central mean sensitivity (CMS) assessed by standard automated perimetry.

METHODS

Fifty-four eyes with open angle glaucoma were scanned using a swept-source OCTA (Plex Elite 9000, Zeiss, Dublin, CA) and macular vascular microcirculation was measured by calculating the overall flux and vessel area density (VAD) over the entire 6mm x 6mm area, excluding large retinal vessels. Central 10-degree VF CMS was calculated based on 24-2 VF. Pearson correlation was used to investigate the correlation between global and sectoral OCTA parameters and global and sectoral VF CMS.

RESULTS

Both global GCIPL flux and VAD were significantly correlated with VF CMS (p<0.001). For the sectoral analysis, sectoral VAD was significantly correlated with sectoral VF CMS in all comparisons except for the inferonasal VF CMS with supero-temporal (ST) GCIPL VAD (p = 0.097). Although highest correlation was observed for both ST VF CMS with inferior GCIPL VAD and infero-temporal VF CMS with superior GCIPL VAD (r = 0.683, p<0.001), there was no significant difference in correlation when compared to the global VAD and other sectors' correlation coefficients (p≥ 0.091), except for the ST GCIPL VAD (p = 0.001).

CONCLUSIONS

Global and sectoral macular vascular microcirculation in the GCIPL, as determined by OCTA, was significantly correlated with global and sectoral VF CMS in glaucomatous patients. OCTA can aid in the understanding of the structure-function relationships of the macular region.