Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy

Three-dimensional structural and angiographic evaluation of foveal ischemia in diabetic retinopathy: method and validation

Optical coherence tomography angiography (OCTA) allows us to noninvasively investigate foveal ischemia, a key feature of diabetic retinopathy (DR). However, the sizes of the foveal avascular zone (FAZ) have a significant variation in normal population, preventing the objective assessment of pathological enlargement of FAZ due to capillary dropout. Based on the relationship between FAZ and ganglion cell complex (GCC) thickness in normal eyes, we defined a theoretical baseline FAZ (tbFAZ) on structural OCT and measured 2D and 3D vessel density in its vicinity on the simultaneously acquired OCTA in normal and diabetic eyes. We found that the structure-based tbFAZ was a reliable reference to identify foveal ischemia and that the 3D vessel density demonstrated ischemia more effectively than the 2D method. The proposed 3D para-FAZ vessel density correlates well with DR severity and potentially is a useful diagnostic biomarker, especially in the early stages of DR.

Controlling for Artifacts in Widefield Optical Coherence Tomography Angiography Measurements of Non-Perfusion Area

The recent clinical adoption of optical coherence tomography (OCT) angiography (OCTA) has enabled non-invasive, volumetric visualization of ocular vasculature at micron-scale resolutions. Initially limited to 3 mm × 3 mm and 6 mm × 6 mm fields-of-view (FOV), commercial OCTA systems now offer 12 mm × 12 mm, or larger, imaging fields. While larger FOVs promise a more complete visualization of retinal disease, they also introduce new challenges to the accurate and reliable interpretation of OCTA data. In particular, because of vignetting, wide-field imaging increases occurrence of low-OCT-signal artifacts, which leads to thresholding and/or segmentation artifacts, complicating OCTA analysis. This study presents theoretical and case-based descriptions of the causes and effects of low-OCT-signal artifacts. Through these descriptions, we demonstrate that OCTA data interpretation can be ambiguous if performed without consulting corresponding OCT data. Furthermore, using wide-field non-perfusion analysis in diabetic retinopathy as a model widefield OCTA usage-case, we show how qualitative and quantitative analysis can be confounded by low-OCT-signal artifacts. Based on these results, we suggest methods and best-practices for preventing and managing low-OCT-signal artifacts, thereby reducing errors in OCTA quantitative analysis of non-perfusion and improving reproducibility. These methods promise to be especially important for longitudinal studies detecting progression and response to therapy.

Near infrared adaptive optics flood illumination retinal angiography

Image-based angiography is a well-adapted technique to characterize vasculature, and has been used in retinal neurovascular studies. Because the microvasculature is of particular interest, being the site of exchange between blood and tissue, a high spatio-temporal resolution is required, implying the use of adaptive optics ophthalmoscopes with a high frame rate. Creating the opportunity for decoupled stimulation and imaging of the retina makes the use of near infrared (NIR) imaging light desirable, while the need for a large field of view and a lack of distortion implies the use of a flood illumination-based setup. However, flood-illumination NIR video sequences of erythrocytes, or red blood cells (RBC), have a limited contrast compared to scanning systems and visible light. As a result, they cannot be processed via existing image-based angiography methods. We have therefore developed a new computational method relying on a spatio-temporal filtering of the sequence to isolate blood flow from noise in low-contrast sequences. Applying this computational approach enabled us to perform angiography with an adaptive optics flood illumination ophthalmoscope (AO-FIO) using NIR light, both in bright-field and dark-field modalities. Finally, we demonstrate the capabilities of our system to differentiate blood flow velocity on a retinal capillary network in vivo.

Optical coherence tomography angiography analysis of macular vessel density before and after anti-VEGF therapy in eyes with diabetic retinopathy

PURPOSE

To evaluate changes in macular vessel density following intravitreal anti-VEGF injection in patients with diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR).

METHODS

In this retrospective case series, optical coherence tomography angiography (OCTA) images from 55 eyes of 35 patients with either DME (46 eyes) or PDR (9 eyes) were included. Macular capillary vessel density at the level of the superficial retinal capillary plexus (SCP), deep retinal capillary plexus (DCP) and total retinal capillary plexus (TCP) before and after anti-VEGF treatment was calculated. Longitudinal changes in vessel density following serial anti-VEGF treatment were analyzed in a subset of eyes.

RESULTS

Vessel density in the SCP, DCP or TCP was not found to be significantly different after one, two or three intravitreal injections (p > 0.05 for all time points). Subgroup analysis revealed no significant change in the DME and PDR subgroups (all p > 0.05). Multivariate analysis revealed no effect of type of injected anti-VEGF agent or presence of previous treatment on VD measurements (all p > 0.05). There was no correlation between the anatomic response of DME to treatment and VD measurements.

CONCLUSIONS

In this study, macular vessel density remained statistically unchanged following up to three intravitreal injections of any anti-VEGF agent. This indicates that there may not be an early effect of anti-VEGF treatment on macular vessel density and its effect on macular perfusion may not be a direct change in microvascular flow.

Quantitative analysis of retinal and choroid capillary ischaemia using optical coherence tomography angiography in type 2 diabetes

PURPOSE

To perform a quantitative analysis of retinal and choroid capillary ischaemia in diabetic patients by using optical coherence tomography angiography (OCTA).

METHODS

A total of 97 type 2 diabetic patients and 48 controls were included in this cross-sectional study. Diabetic patients without diabetic retinopathy (DR) were categorized as no DR (NDR) group; DR was classified into mild non-proliferative diabetic retinopathy (NPDR), moderate NPDR, severe NPDR and proliferative diabetic retinopathy (PDR). Quantitative parameters included foveal and parafoveal vascular density (VD) in superficial, deep and choroid capillary plexus (SCP, DCP and CCP), and foveal flow area in CCP. Stepwise comparisons between groups were performed in the adjacent stages.

RESULTS

Diabetic patients had significantly lower flow area in CCP and VD in all three layers compared with controls. In NDR group, foveal flow area in CCP significantly decreased compared with controls. In mild NPDR, parafoveal VD significantly decreased in all three layers compared with NDR, especially in temporal and nasal areas. In moderate NPDR, VD reduction extended to the inferior area in SCP and DCP compared with mild NPDR. In severe NPDR, progressive losses of VD were presented in all layers compared with moderate NDPR. In PDR, the superior VD in SCP significantly increased compared with severe NPDR.

CONCLUSION

In diabetic patients, the microvascular ischaemia originated in choroid layer and extended inward affecting the deep and superficial layer. OCTA can serve as a reliable method for early detection and to monitor progressions in diabetic retinopathy.

Correlation of retinal vascular perfusion density with dark adaptation in diabetic retinopathy

PURPOSE

To evaluate the anatomic versus functional changes in diabetic retinopathy (DR) by studying the correlation of retinal vascular perfusion density and dark adaptation (DA).

METHODS

Optical coherence tomography angiography (OCTA) and DA tests were performed in diabetic patients and nondiabetic controls. DA was measured using AdaptDx dark adaptometer and the rod intercept was recorded. Macular OCTA images were acquired using the RTVue XR Avanti with AngioVue.

RESULTS

Eighty-six eyes from 57 patients with diabetes (19 with no DR, 19 with non-proliferative DR [NPDR], and 19 with proliferative DR [PDR] who had undergone photocoagulation) and 10 eyes from 10 patients without diabetes were recruited. A significant decrease in vascular density and a prolonged rod intercept were found as DR progressed (P < .01). A negative trend was found between vascular density and the rod intercept. The negative trend in the deep layer (R² = 0.28) was more substantial than that in the superficial layer (R² = 0.14). A prolonged rod intercept was associated with elevated HbA1c (R² = 0.08).

CONCLUSIONS

The vascular density of the macula could be assessed by OCTA and the functional change in the outer retina could be measured non-invasively by DA. The severity of decreasing vascular density and prolongation of DA are proportional to progression of DR. Decreased deep retinal vascular perfusion density and impaired DA response are correlated and show a negative trend according to the severity of DR.

Statistical Model of Optical Coherence Tomography Angiography Parameters That Correlate With Severity of Diabetic Retinopathy

Purpose

To determine whether combining quantitative optical coherence tomography angiography (OCTA) parameters can achieve high sensitivity and specificity to distinguish eyes with nonproliferative diabetic retinopathy (NPDR) from those with proliferative diabetic retinopathy (PDR) as well as eyes with diabetes and no DR (NoDR) from those with clinical DR (any DR).

Methods

This cross-sectional study included 28 eyes (17 patients) with NoDR, 54 eyes (34 patients) with NPDR, and 56 eyes (36 patients) with PDR. OCTA images were processed to quantify the foveal avascular zone (FAZ) area, acircularity, vessel density, skeletonized vessel density, fractal dimension, and intersections and average vessel diameter for the superficial (SCP) and the deep capillary plexus (DCP). Binary logistic regression models were used to identify the OCTA parameters that best distinguished DR severity groups. The area (AUC) under the receiver operating characteristic (ROC) curves, and sensitivity and specificity were calculated for each model.

Results

The regression model identified the SCP FAZ area, DCP vessel density, and acircularity as parameters that best distinguished between DR severity groups. ROC curves for NPDR versus PDR had an AUC of 0.845 (P < 0.001) and sensitivity and specificity of 86% and 70%, respectively. ROC curves for NoDR versus any DR showed an AUC of 0.946 (P < 0.001) with sensitivity of 89% and specificity of 96%, with comparable results when explored in males and females separately.

Conclusions

We identified a set of OCTA parameters with high sensitivity and specificity for distinguishing between groups based on DR severity, suggesting potential clinical application for OCTA as a screening tool for DR.

Visualizing Structure and Vascular Interactions: Macular Nonperfusion in Three Capillary Plexuses

BACKGROUND AND OBJECTIVE

To assess the relationship between retinal vascular and structural changes in the superficial, middle, and deep capillary plexuses (SCP, MCP, DCP) using optical coherence tomography angiography (OCTA) and en face OCT.

PATIENTS AND METHODS

Patients with diabetic retinopathy were imaged using the Cirrus HD-OCT with AngioPlex. Using manual segmentation of the retinal layers, the authors compared OCTA to en face OCT images to examine corresponding patterns in each of the three capillary plexuses.

RESULTS

Areas of decreased perfusion and capillary dropout on OCTA were found to be associated with three corresponding lesions on en face OCT: hyporeflectivity, cystic edema, and hard exudates. Vascular changes in individual capillary plexuses corresponded with structural changes in their respective perfused retinal layers.

CONCLUSIONS

Using manual segmentation on OCTA, the authors provide a framework to visualize the relationship between vascular pathology on OCTA and structural changes on en face OCT within specific capillary plexuses. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e182-e190.].

Reproducibility of macular and optic nerve head vessel density measurements by swept-source optical coherence tomography angiography

PURPOSE

To assess the reproducibility of swept-source optical coherence tomography angiography (SS-OCTA) for macular and optic nerve head (ONH) vessel density (VD).

METHODS

Cross-sectional study using the Triton OCTA (Topcon, Tokyo, Japan), for VD (%) measurements in 40 eyes of 40 healthy subjects on two 6 × 6 mm scans of the macula and ONH across five subfields (central, superior, inferior, temporal, and nasal) at different segmentation levels: superficial capillary plexus (SCP), deep capillary plexus (DCP), outer retina, and choriocapillaris. Reproducibility values were summarized as intraclass correlation coefficients (ICCs) and coefficients of variations (CV).

RESULTS

ICCs for the macular VD measurements in the central zone were 0.874, 0.770, 0.575, 0.718 at the levels SCP, DCP, outer retina, and choriocapillaris, respectively, while worse ICCs were obtained for the parafoveal subfields (ICC ⩽ 0.589); CVs were 2.8%-6.7%. The reproducibility of the ONH superficial VD was ICC = 0.941 for the papillary region and was ICC = 0.499-0.853 for the peripapillary zone; CVs ranged from 4.8% to 17%. Peripapillary VD showed an ICC = 0.533-0.770 in the DCP layer, and 0.572-0.828 in the choriocapillaris. Lowest VD were obtained for the macular SCP and DCP (23% and 22%, respectively), in the foveal zone, while greatest VD were recorded in the nasal and temporal peripapillary subfields at the level of the choriocapillaris (both 68%).

CONCLUSIONS

The new SS-OCTA software served to quantify macular and ONH VD with a reproducibility that was good in the central zones (foveal and papillary, respectively) and moderate in the peripheral zones (parafoveal and peripapillary).

Longitudinal Quantification of Retinal Nonperfusion in the Macula of Eyes With Retinal Vein Occlusion Receiving Anti-VEGF Therapy: Secondary Analysis of the WAVE Randomized Trial

BACKGROUND AND OBJECTIVE

Longitudinal quantification of retinal nonperfusion (RNP) in eyes with retinal vein occlusion (RVO) undergoing anti-vascular endothelial growth factor therapy.

PATIENTS AND METHODS

Thirty eyes with ischemic RVO were randomized to ranibizumab (Lucentis; Genentech, South San Francisco, CA) (monotherapy) or ranibizumab plus peripheral laser (combination therapy) in a 12-month, prospective trial. RNP on fluorescein angiography was quantified within the macula through 12 months of follow-up.

RESULTS

Baseline mean macular RNP areas were 5.04 mm² and 8.30 mm² in the monotherapy (n = 5) and combination therapy (n = 15) cohorts, respectively. Through month 12, mean macular RNP area increased 0.36 mm² and 0.53 mm² in the monotherapy and combination therapy cohorts, respectively (P = .77). Marked, progressive RNP was observed in three eyes (12%). No areas of reperfusion were detected in any eye.

CONCLUSION

Among ischemic RVO eyes in WAVE, macular RNP was common at baseline and remained stable over time in most eyes, though marked RNP progression occurred in a minority of eyes. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:258-264.].

Enlargement of the foveal avascular zone detected by optical coherence tomography angiography in diabetic children without diabetic retinopathy

PURPOSE

Evaluation of foveal avascular zone (FAZ) in children with diabetes (DM) using OCTA.

METHODS

We examined 112 diabetic children without DR aged 6-18 years and 30 age-matched controls using Topcon OCT Angiography and measured FAZ in superficial (SCP) and deep capillary plexus (DCP). The study group was divided into three subgroups depending on DM duration group 1: < 5 years (n = 40), group 2: 5-10 years (n = 42), group 3: > 10 years (n = 30).

RESULTS

The mean DCP FAZ increased with DM duration from 502.2 μm² (SD 137.8) in group 1 to 523.9 μm² (SD 159.2) in group 2 and 539.7 μm² (SD 189.1) in group 3. Control group differed significantly from group 1 (p = 0.0120), group 2 (p = 0.0019) and group 3 (p = 0.0011). The mean DCP to SCP FAZ surface ratio was 1.88 (SD 0.68) in the study vs 1.58 (SD 0.48) in the control group (p = 0.0232). The DCP and SCP FAZ surface difference was 217.6 μm² (SD 100.8 μm²) in diabetics vs. 124.2 μm² (SD 72.8 μm²) in controls (p < 0.0001). In the control group, it was significantly smaller than in group 1 (p < 0.006), group 2 (p < 0.0001) and group 3 (p < 0.0001).

CONCLUSIONS

Changes can be detected in FAZ of diabetic children before DR development which can be vital for screening.

Automatic segmentation of the foveal avascular zone in ophthalmological OCT-A images

Angiography by Optical Coherence Tomography (OCT-A) is a non-invasive retinal imaging modality of recent appearance that allows the visualization of the vascular structure at predefined depths based on the detection of the blood movement through the retinal vasculature. In this way, OCT-A images constitute a suitable scenario to analyze the retinal vascular properties of regions of interest as is the case of the macular area, measuring the characteristics of the foveal vascular and avascular zones. Extracted parameters of this region can be used as prognostic factors that determine if the patient suffers from certain pathologies (such as diabetic retinopathy or retinal vein occlusion, among others), indicating the associated pathological degree. The manual extraction of these biomedical parameters is a long, tedious and subjective process, introducing a significant intra and inter-expert variability, which penalizes the utility of the measurements. In addition, the absence of tools that automatically facilitate these calculations encourages the creation of computer-aided diagnosis frameworks that ease the doctor’s work, increasing their productivity and making viable the use of this type of vascular biomarkers. In this work we propose a fully automatic system that identifies and precisely segments the region of the foveal avascular zone (FAZ) using a novel ophthalmological image modality as is OCT-A. The system combines different image processing techniques to firstly identify the region where the FAZ is contained and, secondly, proceed with the extraction of its precise contour. The system was validated using a representative set of 213 healthy and diabetic OCT-A images, providing accurate results with the best correlation with the manual measurements of two experts clinician of 0.93 as well as a Jaccard’s index of 0.82 of the best experimental case in the experiments with healthy OCT-A images. The method also provided satisfactory results in diabetic OCT-A images, with a best correlation coefficient with the manual labeling of an expert clinician of 0.93 and a Jaccard’s index of 0.83. This tool provides an accurate FAZ measurement with the desired objectivity and reproducibility, being very useful for the analysis of relevant vascular diseases through the study of the retinal micro-circulation.

Evaluation of Automatically Quantified Foveal Avascular Zone Metrics for Diagnosis of Diabetic Retinopathy Using Optical Coherence Tomography Angiography

Purpose

To describe an automated algorithm to quantify the foveal avascular zone (FAZ), using optical coherence tomography angiography (OCTA), and to compare its performance for diagnosis of diabetic retinopathy (DR) and association with best-corrected visual acuity (BCVA) to that of extrafoveal avascular area (EAA).

Methods

We obtained 3 × 3-mm macular OCTA scans in diabetic patients with various levels of DR and healthy controls. An algorithm based on a generalized gradient vector flow (GGVF) snake model detected the FAZ, and metrics assessing FAZ size and irregularity were calculated. We compared the automated FAZ segmentation to manual delineation and tested the within-visit repeatability of FAZ metrics. The correlations of two conventional FAZ metrics, two novel FAZ metrics, and EAA with DR severity and BCVA, as determined by Early Treatment Diabetic Retinopathy Study (ETDRS) charts, were assessed.

Results

Sixty-six eyes from 66 diabetic patients and 19 control eyes from 19 healthy participants were included. The agreement between manual and automated FAZ delineation had a Jaccard index > 0.82, and the repeatability of automated FAZ detection was excellent in eyes at all levels of DR severity. FAZ metrics that incorporated both FAZ size and shape irregularity had the strongest correlation with clinical DR grade and BCVA. Of all the tested OCTA metrics, EAA had the greatest sensitivity in differentiating diabetic eyes without clinical evidence of retinopathy, mild to moderate nonproliferative DR (NPDR), and severe NPDR to proliferative DR from healthy controls.

Conclusions

The GGVF snake algorithm tested in this study can accurately and reliably detect the FAZ, using OCTA data at all DR severity grades, and may be used to obtain clinically useful information from OCTA data regarding macular ischemia in patients with diabetes. While FAZ metrics can provide clinically useful information regarding macular ischemia, and possibly visual acuity potential, EAA measurements may be a better biomarker for DR.

Retinal Microvasculature and Visual Acuity after Intravitreal Aflibercept in Diabetic Macular Edema: An Optical Coherence Tomography Angiography Study

We investigated changes in retinal vascular area and the foveal avascular zone (FAZ) after intravitreal aflibercept in diabetic macular edema (DME) and the association of these changes with visual outcomes. The retinal vascular area in the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) and the FAZ area were measured using optical coherence tomography angiography (OCTA) in 23 eyes of 23 patients with DME, before and after intravitreal aflibercept. Overall, there was no significant change in retinal vascular area or FAZ. Better BCVA after treatment was significantly associated with larger retinal vascular area in the SCP and the DCP, both at baseline (R² = 0.512, P < 0.001 and R² = 0.361, P = 0.002, respectively) and after intravitreal aflibercept (R² = 0.717, P < 0.001 and R² = 0.618, P < 0.001, respectively). MAs were observed in the DCP in 20 eyes (87%), but only detected in four eyes (17%) in the SCP before treatment. The number of eyes with MAs in the DCP significantly decreased to 13 (57%) after treatment (P = 0.049). The persistence of DME was associated with persistent MAs (P = 0.019) and less visual gain (P = 0.031) following treatment. Thus, preserving retinal perfusion and the resolution of MAs are associated with better vision and resolution of the DME after intravitreal aflibercept.

Importance of Considering the Middle Capillary Plexus on OCT Angiography in Diabetic Retinopathy

Purpose

To quantify microvasculature changes in the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP) in diabetic retinopathy (DR).

Methods

Retrospective cross-sectional study at a tertiary academic referral center, in which 26 controls (44 eyes), 27 diabetic subjects without retinopathy (44 eyes), 32 subjects with nonproliferative retinopathy (52 eyes), and 27 subjects with proliferative retinopathy (40 eyes) were imaged with optical coherence tomography angiography (OCTA). Outcome measures included parafoveal vessel density (VD), percentage area of nonperfusion (PAN), and adjusted flow index (AFI) at the different plexuses.

Results

MCP VD and MCP AFI decreased with worsening DR, while PAN increased, mirroring changes within the DCP. The fitted regression line for MCP and DCP AFI were significantly different than the SCP, while DCP PAN differed from SCP PAN with disease progression. Higher SCP AFI and PAN were different in eyes with diabetes without retinopathy compared with controls. Unexpectedly, sex was found to independently influence MCP VD and AFI with worsening disease.

Conclusions

OCTA parameters in the MCP and DCP displayed parallel changes with DR progression, different from the SCP, emphasizing the importance of physiologic considerations in the retinal capillaries. Thus, segmentation protocols that include the MCP within the SCP may be confounded. A difference in DCP PAN with worsening DR was unmasked relative to a prior study that included the MCP with SCP. We confirm that SCP AFI and PAN may serve as early indicators of microvascular changes in DR and identify an interaction between sex and the MCP deserving further study.

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

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

Enhanced Quantification of Retinal Perfusion by Improved Discrimination of Blood Flow From Bulk Motion Signal in OCTA

Purpose

Quantification of optical coherence tomography angiography (OCTA) is confounded by the prevalence of bulk motion. We have previously developed a regression-based bulk motion subtraction (rb-BMS) algorithm that estimates bulk motion velocity and corrects for its effect on flow signal. Here, we aim to investigate its ability to improve the reliability of capillary density (CD) quantification.

Methods

Two spectral-domain systems (70-kHz Avanti/AngioVue and 68-kHz Cirrus/AngioPlex) acquired 6 × 6-mm OCTA scans. The rb-BMS algorithm was applied on each OCTA volume. Regression analysis of angiographic versus reflectance signal of avascular A-lines in B-frames was used to set an optimized reflectance-adjusted threshold for discriminating vascular versus nonvascular voxels. The CD was calculated from en face maximum projections of the superficial vascular complex in macular scans and the nerve fiber layer plexus in disc scans, excluding large vessels. The retinal signal strength (RSS) was calculated by averaging the logarithmic-scale OCT reflectance signal, and its correlation with CD was investigated.

Results

Eight healthy eyes were scanned with each instrument on 2 separate days. The rb-BMS algorithm improved within-visit repeatability and between-visit reproducibility of CD compared with a global-threshold measurement algorithm. Using the rb-BMS algorithm, the CD results were less affected by RSS and the population variation was reduced. Motion-induced line artifacts were also reduced.

Conclusions

The rb-BMS algorithm improved the reliability of perfusion quantification in OCTA on both Food and Drug Administration-cleared spectral-domain OCTA systems.

Translational Relevance

The rb-BMS method helped reduce the inter-scan variability by generating accurate vessel maps, improving the reliability of retinal perfusion quantification.

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

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

Longitudinal Wide-Field Swept-Source OCT Angiography of Neovascularization in Proliferative Diabetic Retinopathy after Panretinal Photocoagulation

PURPOSE

Wide-field swept-source (SS) OCT angiography (OCTA) was compared with ultrawide-field (UWF) fluorescein angiography (FA) for evaluating neovascularization (NV) before and after panretinal photocoagulation (PRP) in eyes with treatment-naive proliferative diabetic retinopathy (PDR).

DESIGN

Prospective, observational, consecutive case series.

PARTICIPANTS

Patients with treatment-naive PDR.

METHODS

Patients were imaged using the SS OCTA 12 × 12-mm field of view (PLEX Elite 9000; Carl Zeiss Meditec, Inc, Dublin, CA) at baseline and at 1 week, 1 month, and 3 months after PRP. Select eyes were imaged with 5 SS OCTA 12 × 12-mm scans to create posterior pole montages. Ultrawide-field fundus photography and UWF FA were obtained at baseline and 3 months after PRP.

MAIN OUTCOME MEASURES

Neovascularization visualized using wide-field SS OCTA and UWF FA.

RESULTS

From January through May 2018, wide-field SS OCTA was performed on 20 eyes with treatment-naive PDR from 15 patients. The en face SS OCTA 12 × 12-mm vitreoretinal interface (VRI) slab images showed NV at baseline in 18 of 20 eyes (90%). Of the remaining 2 eyes, the posterior pole montage captured peripheral NV in one eye, and in the other eye, no evidence of NV was detected with either UWF FA or SS OCTA. After PRP, both SS OCTA and FA demonstrated similar progression or regression of NV, but SS OCTA provided more detailed visualization of the vascular changes.

CONCLUSIONS

Neovascularization in PDR can be identified at baseline and imaged serially after PRP using wide-field SS OCTA. In patients with a high clinical suspicion for PDR, wide-field SS OCTA likely will be the only imaging method needed for diagnosis and longitudinal evaluation of NV.

Optical coherence tomography angiography analysis of changes in the retina and the choroid after haemodialysis

The purpose of this study is to evaluate the effect of haemodialysis on perfused vessel density, choroidal thickness (CT), and retinal thickness in end-stage renal disease (ESRD) using swept-source optical coherence tomography angiography (SS-OCTA). We studied twenty-nine eyes of 29 ESRD patients by ophthalmologic examination and SS-OCTA before and after haemodialysis. The colour-coded perfusion density maps were generated and perfused vessel density was calculated. Changes in systemic and other ocular parameters such as retinal and choroidal thickness were measured and analysed. Total perfused vessel density decreased significantly after haemodialysis in the choriocapillaris; it was not significantly different in the superficial capillary plexus (SCP) and the deep capillary plexus (DCP). Total CT decreased significantly, but total retinal thickness was not significantly different. There was no significant correlation between choriocapillaris perfused vessel density and CT. The reduction in choriocapillaris perfused vessel density correlated with the decrease in systolic and mean arterial blood pressures. The decrease in CT correlated with the ultrafiltration volume. There were no significant systemic and ocular factors affecting change in retinal thickness and perfused vessel density of SCP and DCP. This is the first study to assess the effect of haemodialysis on blood flow changes using SS-OCTA; changes may be more prominent in the choroidal compared to the retinal layer.

A quantitative comparison of five optical coherence tomography angiography systems in clinical performance

AIM

To compare the clinical performance of 4 spectral-domain (SD) optical coherence tomography angiography (OCTA) systems: AngioVue™, AngioPlex™, Spectralis^® OCTA, AngioScan, and 1 swept-source (SS) OCTA SS OCT Angio™.

METHODS

Twenty-seven undilated right eyes of 27 participants underwent OCTA examination using five different systems respectively for both 3×3 and 6×6 mm² scan pattern (Spectralis OCTA for 3×3 mm² scan only). Image quality, including vessel valid visibility and the number of motion artifacts, and acquisition time were evaluated. Repeated measures analysis of variance (ANOVA) with Bonferroni's post-test and Friedman test with Dunn's post-test were used to compare measurements.

RESULTS

The age of the subjects was 28.19±5.55y (range, 23-49y). The spherical equivalent refraction was -2.55±1.84 D (range, 0.00 to -5.25 D). Significant difference was observed in the evaluation of vessel valid visibility (AngioVue the highest: 0.111±0.031 for 3×3 mm² scan and 0.128±0.020 for 6×6 mm² scan), number of motion artifacts (AngioVue the fewest: 0.778±1.086 for 3×3 mm² scan and 0.333±0.620 for 6×6 mm² scan) and acquisition time (AngioPlex the shortest: 8.537±1.921s for 3×3 mm² scan and 8.298±1.741s for 6×6 mm² scan; all P<0.001).

CONCLUSION

There is poor agreement of measurements among systems. AngioVue provides images with the highest vessel valid visibility and the fewest motion artifacts. AngioPlex achieves the shortest acquisition.

The diagnostic value of optical coherence tomography angiography in diabetic retinopathy: a systematic review

PURPOSE

Diabetic retinopathy (DR) is one of the leading causes of blindness worldwide. Accurate investigative tools are essential for the early diagnosis and monitoring of the disease. Optical coherence tomography angiography (OCTA) is a recently developed technology that enables visualisation of the retinal microvasculature.

METHODS

A systematic review of the literature was performed to examine the diagnostic use of OCTA in DR to date. Medline, EMBASE, and Cochrane databases were searched to find relevant studies. Sixty-one original studies were selected for the review.

RESULTS AND DISCUSSION

OCTA has demonstrated the ability to identify microvascular features of DR such as microaneurysms, neovascularisation, and capillary non-perfusion. Furthermore, OCTA is enabling quantitative evaluation of the microvasculature of diabetic eyes. It has demonstrated the ability to detect early microvascular changes, in eyes with or without clinically evident DR. It has also been shown to detect progressive changes in the foveal avascular zone, and vascular perfusion density, with worsening severity of disease. It provides three-dimensional visualisation of the individual retinal vascular networks and is thereby enhancing our understanding of the role of the deeper vasculature in the pathogenesis of diabetic retinopathy and maculopathy.

CONCLUSION

However, limitations exist with current OCTA technology, in respect to the small field of view, image quality, projection artefact, and inaccuracies in analysis of the deeper vascular layers. While questions remain regarding its practical applicability in its present form, with continuing development and improvement of the technology, the diagnostic value of OCTA in diabetic retinopathy is likely to become evident.

Variability of Foveal Avascular Zone Metrics Derived From Optical Coherence Tomography Angiography Images

Purpose

To characterize sources of inter- and intrasubject variability in quantitative foveal avascular zone (FAZ) metrics.

Methods

Two 3×3-mm optical coherence tomography angiography scans (centered on the fovea) were acquired in both eyes of 175 subjects. An image of the superficial plexus was extracted from each scan and segmented twice by a single observer. Four quantitative FAZ morphology metrics (area, axis ratio, acircularity, major horizontal axis angle) were calculated, and a variance components analysis was performed.

Results

Mean (±SD) age was 27.9 ± 11.9 years, and 55% were female. Area had the largest amount of variance resulting from intersubject differences (93.1%). In contrast, there was large interocular variance for axis ratio, acircularity, and major horizontal axis angle (55.0%, 53.7%, 70.7%, respectively), though only axis ratio showed significant asymmetry between fellow eyes (P < 0.05). Neither repeated images from the same eye nor repeated segmentation on the same image were significant sources of variance.

Conclusions

Metrics of FAZ morphology show excellent repeatability and reliability. Excluding FAZ area, there was a high amount of variance attributed to interocular differences for the other FAZ metrics; therefore, the fellow eye should not be considered a control for FAZ studies when using these metrics.

Translational Relevance

Vision scientists must be prudent when choosing FAZ metrics, as they display varying degrees of within-subject differences relative to between-subject differences. It seems likely that different metrics will be best suited for different tasks, such as monitoring small changes over time within a single subject or assessing whether a given FAZ is abnormal.

Analysis of Foveal Microvascular Abnormalities in Diabetic Retinopathy Using Optical Coherence Tomography Angiography with Projection Artifact Removal

PURPOSE

To analyze foveal microvascular abnormalities in different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA) with projection artifact removal (PAR).

METHODS

We analyzed 93 eyes of 59 patients with diabetes-31 with no DR (no DR), 34 with mild to moderate nonproliferative DR (mild DR), and 28 with severe nonproliferative DR to proliferative DR (severe DR)-and 31 age-matched healthy controls. Sections measuring 3 × 3 mm2 centered on the fovea were obtained using OCTA. The area, perimeter, and acircularity index (AI) of the foveal avascular zone (FAZ), vessel density within a 300 μm wide region of the FAZ (FD-300), and parafoveal vessel density in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were calculated using novel built-in software with PAR.

RESULTS

There was no statistically significant difference in the FAZ area (p=0.162). There was a statistically significant difference in the FAZ perimeter (p=0.010) and the AI (p < 0.001) between the four groups. There was a correlation between the AI and the increasing severity of DR (p=0.010). Statistically significant decreases of vessel density in the FD-300, SCP, and DCP were observed (all p < 0.001). There was a difference in parafoveal vessel density in the DCP between the healthy control eyes and the eyes with diabetes without DR (p=0.027). There was a significant correlation between vessel density and increasing severity of DR (p < 0.001).

CONCLUSION

Compared with the FAZ area, AI allows a more helpful quantitative assessment of the changes in the FAZ. Vessel density determined using OCTA with PAR might be a useful parameter indicating the progression of DR. Parafoveal vessel density in the DCP after PAR might be a potential early biomarker of DR before appearance of clinically evident retinopathy and needs further investigation.

VALUE OF FRACTAL ANALYSIS OF OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN VARIOUS STAGES OF DIABETIC RETINOPATHY

PURPOSE

To use fractal dimensional analysis to investigate retinal vascular disease patterns in patients with diabetic retinopathy using spectral domain optical coherence tomography angiography.

METHODS

A retrospective study was conducted which included 49 eyes from 26 control subjects and 58 eyes from 35 patients known to have diabetic retinopathy. Of the 58 eyes with known retinopathy, 31 were categorized as nonproliferative diabetic retinopathy (13 mild, 9 moderate, and 9 severe) and 27 were categorized as proliferative diabetic retinopathy. Optical coherence tomography angiography images were acquired using the RTVue XR Avanti (Optovue, Inc). Automated segmentation was obtained through both the superficial and deep capillary plexuses for each eye. Grayscale optical coherence tomography angiography images were standardized and binarized using ImageJ (National Institutes of Health). Fractal box-counting analyses were conducted using Fractalyse (ThéMA). Fractal dimensions (FDs) and correlation coefficient of the superficial and deep capillary plexuses were compared between control eyes and those in various stages of diabetic retinopathy.

RESULTS

The superficial and deep capillary plexuses from diabetic and control eyes were analyzed. The average FD for diabetic eyes was significantly lower than in control eyes in the superficial plexus (P = 2.4 × 10) and in the deep capillary plexus (P = 1.87 × 10 ) with a more statistically significant difference noted in the deep capillary plexus. When analyzing diabetic patients without edema noted on optical coherence tomography, the FD was significantly reduced in the superficial (P = 0.001) and deep (P = 1.49 × 10) plexuses. When analyzing diabetic patients with edema noted on optical coherence tomography, the FD was significantly reduced in the superficial (P = 2.0 × 10) and deep (P = 1.85 × 10) plexuses.

CONCLUSION

The optical coherence tomography angiography FD is significantly lower in both superficial and deep capillary plexuses in eyes with all stages studied of diabetic retinopathy. The results were more often significant for the deep capillary plexus. The use of fractal analysis provides an objective criterion to assess microvascular disease burden in diabetic retinopathy.

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

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

Ultra-wide optical coherence tomography angiography in diabetic retinopathy

Background

To implement an ultra-wide optical coherence tomography angiography imaging (UW-OCTA) modality in eyes with diabetic retinopathy (DR) with the aim of quantifying the burden of microvascular disease at baseline and subsequent clinic visits.

Methods

UW-OCTA was implemented on a 1,060 nm swept source (SS) OCTA engine running at 100 kHz A-line rate with a motion tracking mechanism. A montage scanning protocol was used to capture a 100-degree field of view (FOV) using a 4×4 grid of sixteen total individual 6×6 mm² scans. Typical OCTA images with a FOV of 3×3, 6×6 and 12×12 mm² were obtained for comparison. DR patients were scanned at baseline and follow-up. They were treated at the clinician's discretion. Vessel density and non-perfusion area maps were calculated based on the UW-OCTA images.

Results

Three proliferative DR patients were included in the study. UW-OCTA images provided more detailed visualization of vascular networks compared to 50-degree fluorescein angiography (FA) and showed higher burden of pathology in the retinal periphery that was not captured by typical OCTA. Neovascularization complexes were clearly detected in the two patients with active PDR. Vessel density and non-perfusion maps were used to measure progressive capillary non-perfusion and regression of neovascularization between visits.

Conclusions

UW-OCTA provides approximately 100-degree OCTA images of the fundus comparable to that of wide-angle fundus photography, and may be more applicable in conditions such as DR which affect the peripheral retina in contrast to standard OCTA.

Automatic segmentation of abnormal capillary nonperfusion regions in optical coherence tomography angiography images using marker-controlled watershed algorithm

Diabetic retinopathy (DR) is one of the most complications of diabetes. It is a progressive disease leading to significant vision loss in the patients. Abnormal capillary nonperfusion (CNP) regions are one of the important characteristics of DR increasing with its progression. Therefore, automatic segmentation and quantification of abnormal CNP regions can be helpful to monitor the patient's treatment process. We propose an automatic method for segmentation of abnormal CNP regions on the superficial and deep capillary plexuses of optical coherence tomography angiography (OCTA) images using the marker-controlled watershed algorithm. The proposed method has three main steps. In the first step, original images are enhanced using the vesselness filter and then foreground and background marker images are computed. In the second step, abnormal CNP region candidates are segmented using the marker-controlled watershed algorithm, and in the third step, the candidates are modeled using an undirected weighted graph and finally, by applying merging and removing procedures correct abnormal CNP regions are identified. The proposed method was evaluated on a dataset with 36 normal and diabetic subjects using the ground truth obtained by two observers. The results show the proposed method outperformed some of the state-of-the-art methods on the superficial and deep capillary plexuses according to the most important metrics.

Quantitative evaluation of optical coherence tomography angiography images of diabetic retinopathy eyes before and after removal of projection artifacts

Projection artifacts (PAs) affect the quantification of vascular parameters in the deep layer optical coherence tomography (OCT) angiography image. This study eliminated PA and quantified its effect on imaging. 53 eyes (30 subjects) of normal Indian subjects and 113 eyes (92 patients) of type 2 diabetes mellitus with retinopathy (DR) underwent imaging with a scan area of 3 mm × 3 mm. In this study, a normalized cross-correlation between superficial and deep layer was used to remove PA in deep layer. Local fractal analysis was done to compute vascular parameters such as foveal avascular zone area (mm² ), vessel density (%), spacing between large vessels (%) and spacing between small vessels (%). Before PA removal, vessel density for mild nonproliferative (NPDR), moderate NPDR, severe NPDR and proliferative DR were 42.56 ±1.69%, 40.69 ±0.72%, 37.34 ±0.85% and 35.61 ±1.26%, respectively. After artifact removal, vessel density was 28.9 ±1.22%, 29.9 ±0.56%, 26.19 ±0.59% and 24.02 ±0.94%, respectively. All the vascular parameters were statistically significant (P <.001) between normal and disease eyes, irrespective of superficial and deep retinal layers. Parafoveal sectoral analyses showed that temporal zone had the lowest vessel density and may undergo DR-related changes first. The current approach enabled rapid and accurate quantitative interpretation of DR eyes, without PA.

New Insights On Ocular Sarcoidosis: An Optical Coherence Tomography Angiography Study

Purpose: To report optical coherence tomography angiography (OCT-A) findings in eyes with ocular sarcoidosis (OS) and to compare these findings with those of fluorescein angiography (FA). Methods: Observational, cross-sectional, case-control study. Patients presenting with OS involving the posterior segment were evaluated using FA, structural-OCT and OCT-A. OCT-angiograms of the superficial (SCP) and deep (DCP) capillary plexuses and choriocapillaris (CC) were qualitatively and quantitatively analyzed. Results: OCT-A seemed more sensitive than FA in detecting perifoveal capillary arcade disruptions, areas of hypoperfusion/non-perfusion and capillary abnormalities (p<0.05). Capillary hypoperfusion was more frequently detected in the DCP than in SCP, conversely capillary abnormalities were more often observed at the level of the SCP. Capillary vessel density values were significantly lower in eyes with OS than in healthy controls both at the level of DCP and CC (p<0.05). Conclusion: The depth-resolved nature of OCT-A allowed new insights on OS-induced microvascular and perfusion impairments.

New insights into diabetic retinopathy by OCT angiography

Diabetic retinopathy (DR) is one of the most common diabetic complications, which has become a leading cause for vision loss, mainly because of macular edema and vitreous hemorrhage. Optical coherence tomography (OCT) angiography is a novel technique to visualize vascular changes including microaneurysm, non-perfusion area, intraretinal microvascular abnormalities, and neovascularization. Recently, it is possible to quantify vascular density, foveal avascular zone area, non-perfusion area objectively using OCT angiography. In addition, OCT angiography also provides an alternative method to evaluate the effect of anti-vascular endothelial growth factor (VEGF) treatments by providing high resolution images of macular microcirculatory abnormalities. Thus OCT angiography is an effective method to investigate the vascular changes of the disease, and can also be potentially applied in the diagnosis, treatment, and follow up of DR.

Parafoveal Nonperfusion Analysis in Diabetic Retinopathy Using Optical Coherence Tomography Angiography

Purpose

To describe a new technique for mapping parafoveal intercapillary areas (PICAs) using optical coherence tomography angiography (OCTA), and demonstrate its utility for quantifying parafoveal nonperfusion in diabetic retinopathy (DR).

Methods

Nineteen controls, 15 diabetics with no retinopathy (noDR), 15 with nonproliferative diabetic retinopathy (NPDR), and 15 with proliferative diabetic retinopathy (PDR) were imaged with 10 macular OCTA scans. PICAs were automatically delineated on the averaged superficial OCTA images. Following creation of an eccentricity-specific reference database from the controls, all PICAs greater than 2 SD above the reference means for PICA area and minor axis length were identified as nonperfused areas. Regions of interest (ROI) at 300 μm and 1000 μm from the foveal avascular zone (FAZ) margin were analyzed. Percent nonperfused area was defined as summed nonperfused areas divided by ROI area. Values were compared using Kruskal-Wallis and post-hoc Mann-Whitney U tests.

Results

Median values for total percent nonperfused area at the 300-μm ROI were 2.09, 2.44, 18.08, and 27.55 in the control, noDR, NPDR, and PDR groups, respectively. Median values at the 1000-μm ROI were 3.10, 3.31, 13.42, and 23.00. While there were no significant differences between the control and noDR groups, significant differences were observed between all other groups at both ROIs.

Conclusions

Percent nonperfused area can quantify parafoveal nonperfusion in DR and can be calculated through automatic delineation of PICAs in an eccentricity-specific manner using a standard deviation mapping approach.

Translational Relevance

Percent nonperfused area shows promise as a metric to measure disease severity in diabetic retinopathy.

Optical coherence tomography findings as a predictor of clinical course in patients with branch retinal vein occlusion treated with ranibizumab

PURPOSE

To examine the relationship between optical coherence tomography (OCT) images and clinical course in eyes with branch retinal vein occlusion (BRVO) treated with intravitreal ranibizumab injection (IVR).

DESIGN

Prospective cohort study.

PARTICIPANTS

Thirty eyes of 30 patients with BRVO treated with IVR.

METHODS

All patients received 1 initial IVR followed by repeated injections in the pro re nata (PRN) regimen. Correlations between logarithm of minimum angle of resolution best-corrected visual acuity (logMAR BCVA) or number of IVRs after 12 months and OCT parameters including the external limiting membrane (ELM), ellipsoid zone (EZ), interdigitation zone (IZ), and photoreceptor outer segment (PROS) length at first resolution of macular edema (ME) were assessed. Resolution of ME was defined as central foveal thickness <300 μm and the absence of subretinal fluid. OCT parameters influencing BCVA and number of IVRs were evaluated using multivariate analysis. Correlations between nonperfusion areas (NPAs) and thinning areas and changes in retinal thickness of BRVO-affected areas were assessed.

RESULTS

Of the 30 patients, 27 completed this study and were included in the statistical analyses. The mean logMAR BCVA at 3, 6, and 12 months was 0.16 ± 0.19, 0.09 ± 0.20, and 0.07 ± 0.20, respectively, which improved significantly from baseline at each visit (p < 0.0001, respectively), while the mean number of IVRs at 12 months was 3.9 ± 2.2. The mean number of IVRs for the first resolution of ME was 1.6 ± 0.8. Eyes with ELM and EZ defects at the points of first resolution of ME were correlated with a significantly lower BCVA at 12 months compared with eyes with preserved ELMs and EZs (p = 0.035, p = 0.002, respectively). However, eyes with IZ defects at the points of first resolution of ME were not correlated with a significantly lower BCVA at 12 months compared with eyes with preserved IZs (p = 0.160). Defects in the EZ at the points of first resolution of ME significantly affected the number of IVRs at 12 months (p = 0.042), although the ELM and IZ did not. PROS length at the points of first resolution of ME was significantly correlated with BCVA and number of IVRs at 12 months (p = 0.006, p = 0.0008, respectively). In multivariate analysis, PROS length at the points of first resolution of ME had the most significant effect on BCVA and number of IVRs (p = 0.013, p = 0.012, respectively). NPA size on fluorescein angiography and thinning area on OCT within the macular area showed a significant correlation (p = 0.003, r = 0.971). The retinal thickness of ischemic BRVO-affected areas was significantly less than that of control areas at 10, 11, and 12 months (p = 0.001, p = 0.005, p = 0.003, respectively).

CONCLUSION

We showed that the 1+PRN regimen may be a useful therapy for ME due to BRVO. In addition, PROS length at points of first resolution of ME appears to be a good indicator of BCVA and number of IVRs in BRVO patients.

Optical coherence tomography findings as a predictor of clinical course in patients with branch retinal vein occlusion treated with ranibizumab

Purpose

To examine the relationship between optical coherence tomography (OCT) images and clinical course in eyes with branch retinal vein occlusion (BRVO) treated with intravitreal ranibizumab injection (IVR).

Design

Prospective cohort study.

Participants

Thirty eyes of 30 patients with BRVO treated with IVR.

Methods

All patients received 1 initial IVR followed by repeated injections in the pro re nata (PRN) regimen. Correlations between logarithm of minimum angle of resolution best-corrected visual acuity (logMAR BCVA) or number of IVRs after 12 months and OCT parameters including the external limiting membrane (ELM), ellipsoid zone (EZ), interdigitation zone (IZ), and photoreceptor outer segment (PROS) length at first resolution of macular edema (ME) were assessed. Resolution of ME was defined as central foveal thickness <300 μm and the absence of subretinal fluid. OCT parameters influencing BCVA and number of IVRs were evaluated using multivariate analysis. Correlations between nonperfusion areas (NPAs) and thinning areas and changes in retinal thickness of BRVO-affected areas were assessed.

Results

Of the 30 patients, 27 completed this study and were included in the statistical analyses. The mean logMAR BCVA at 3, 6, and 12 months was 0.16 ± 0.19, 0.09 ± 0.20, and 0.07 ± 0.20, respectively, which improved significantly from baseline at each visit (p < 0.0001, respectively), while the mean number of IVRs at 12 months was 3.9 ± 2.2. The mean number of IVRs for the first resolution of ME was 1.6 ± 0.8. Eyes with ELM and EZ defects at the points of first resolution of ME were correlated with a significantly lower BCVA at 12 months compared with eyes with preserved ELMs and EZs (p = 0.035, p = 0.002, respectively). However, eyes with IZ defects at the points of first resolution of ME were not correlated with a significantly lower BCVA at 12 months compared with eyes with preserved IZs (p = 0.160). Defects in the EZ at the points of first resolution of ME significantly affected the number of IVRs at 12 months (p = 0.042), although the ELM and IZ did not. PROS length at the points of first resolution of ME was significantly correlated with BCVA and number of IVRs at 12 months (p = 0.006, p = 0.0008, respectively). In multivariate analysis, PROS length at the points of first resolution of ME had the most significant effect on BCVA and number of IVRs (p = 0.013, p = 0.012, respectively). NPA size on fluorescein angiography and thinning area on OCT within the macular area showed a significant correlation (p = 0.003, r = 0.971). The retinal thickness of ischemic BRVO-affected areas was significantly less than that of control areas at 10, 11, and 12 months (p = 0.001, p = 0.005, p = 0.003, respectively).

Conclusion

We showed that the 1+PRN regimen may be a useful therapy for ME due to BRVO. In addition, PROS length at points of first resolution of ME appears to be a good indicator of BCVA and number of IVRs in BRVO patients.

Optical Coherence Tomography Angiography in Glaucoma Care

PURPOSE

To provide the reader with information on the principal techniques of optical coherence tomography angiography (OCTA); the current literature on OCTA reproducibility; its applications to glaucoma detection and monitoring of progression; and the role of OCTA in the assessment of the vascular component in glaucoma pathogenesis.

METHODS

A literature review of the pertinent publications for the OCTA in relation to the development, techniques, and its use in glaucoma was carried out.

RESULTS

Rapid improvements in optical coherence tomography (OCT) technology have allowed for enhancement of both image resolution and scanning speed, and the development of vascular assessment modality. OCTA is the non-invasive in vivo imaging of the vasculature located within the retina and optic nerve head area. The principle of OCTA is to use the variations in OCT signals caused by moving particles as the contrast mechanism for imaging of flow. Several algorithms which aim to maximize the contrast signal and minimize the noise have been developed including the phase-based techniques, intensity-based techniques (e.g., split-spectrum amplitude decorrelation angiography (SSADA)), and complex-based techniques (e.g., optical microangiography (OMAG)). With its reliable technique, high image resolution, and current availability, OCTA has been widely used in the assessment of posterior segment diseases including glaucoma in which ocular perfusion dysfunction has been proposed as a pathophysiological mechanism.

CONCLUSION

OCTA may enhance our knowledge of glaucoma pathogenesis and offer an improvement in our ability to detect glaucomatous change.

Advances in Retinal Optical Imaging

Retinal imaging has undergone a revolution in the past 50 years to allow for better understanding of the eye in health and disease. Significant improvements have occurred both in hardware such as lasers and optics in addition to software image analysis. Optical imaging modalities include optical coherence tomography (OCT), OCT angiography (OCTA), photoacoustic microscopy (PAM), scanning laser ophthalmoscopy (SLO), adaptive optics (AO), fundus autofluorescence (FAF), and molecular imaging (MI). These imaging modalities have enabled improved visualization of retinal pathophysiology and have had a substantial impact on basic and translational medical research. These improvements in technology have translated into early disease detection, more accurate diagnosis, and improved management of numerous chorioretinal diseases. This article summarizes recent advances and applications of retinal optical imaging techniques, discusses current clinical challenges, and predicts future directions in retinal optical imaging.

Comparison between optical coherence tomography angiography and fluorescein angiography findings in retinal vasculitis

Background

To describe optical coherence tomography angiography (OCT-A) findings in patients with retinal vasculitis and to compare them to current fluorescein angiography (FA) findings.

Methods

This was an observational case series. Nineteen eyes in 10 patients with retinal vasculitis of various etiologies were imaged with FA (TRC-50DX, Topcon) and OCT-A (SD-OCT, Optovue). The images were reviewed and analyzed.

Results

The mean age was 36 years (range 24-67 years); there were three males and seven females. The primary vessels involved were veins (89%). Fourteen eyes (74%) had active inflammatory disease during the study period, with signs of vascular sheathing and perivascular leakage on FA. Interestingly, in this group, OCT-A was not able to detect clear signs of active inflammation around the affected vessels. Nevertheless, OCT-A was able to detect secondary lesions in fourteen eyes (74%), including some findings not clearly shown on FA. Most of these were within the macular area. OCT-A was particularly effective in cases of capillary dropout, increased foveal avascular zone, telangiectasias, shunts, and areas of neovascularization.

Conclusion

FA remains an essential complementary exam for detection of retinal vasculitis. However, OCT-A extends FA findings and affords better assessment of secondary complications.

Clinical applications of optical coherence tomography angiography: What we have learnt in the first 3 years

A review of the literature from 2014 to 2016 was conducted, focusing on the results of optical coherence tomography angiography in different chorioretinal diseases. In only 3 years, optical coherence tomography angiography has been shown to be an effective tool for diagnosing choroidal neovascularization complicating age-related macular degeneration, pathologic myopia, and inflammatory conditions. The technique has sometimes been considered superior to conventional multimodal imaging, for example, in choroidal neovascularization associated with chronic central serous chorioretinopathy or multifocal choroiditis. In retinal vascular diseases, optical coherence tomography angiography has helped to understand the condition described as paracentral acute middle maculopathy and has been considered highly effective for the analysis of retinal vascular macular changes secondary to retinal vein occlusion or macular telangiectasia. Changes in the foveal avascular zone, also reported in diabetic maculopathy, have been shown to occur before any angiographic signs. A reduction in capillary vascular density has been reported in the fovea of eyes with malignant melanoma, but not in eyes with choroidal nevus. However, optical coherence tomography angiography is a recent technique that probably needs refinements and further studies. Nevertheless, the first 3 years of optical coherence tomography angiography use suggest its clinical relevance and useful applications in daily clinical practice.

Quantitative OCT Angiography Evaluation of Peripapillary Retinal Circulation after Plaque Brachytherapy

OBJECTIVE

To study peripapillary retinal capillary circulation in eyes treated with I-125 plaque brachytherapy for uveal melanoma using optical coherence tomography angiography (OCTA).

DESIGN

Cross-sectional study of 10 subjects imaged with OCTA prior to uveal melanoma treatment and 15 subjects imaged after development of radiation retinopathy and/or optic neuropathy.

PARTICIPANTS

Following IRB approval, subjects were enrolled from an academic ocular oncology clinical practice. All subjects had uveal melanoma in one eye and treatment with I-125 plaque brachytherapy was planned or had previously taken place. Patients with low vision at baseline and uncontrolled hypertension were excluded. In the post-treatment group, seven subjects were male and eight were female; age range 38 to 81 years. Visual acuities in the irradiated eyes ranged from 20/20 to counting fingers. Visual acuities in the untreated fellow eyes were 20/25 or better.

METHODS

Peripapillary retinal capillary circulation was measured by OCTA (Optovue, Inc). 4.5×4.5 mm optic disc scans were obtained. 10 subjects were imaged prior to brachytherapy treatment and 15 subjects were imaged after development of clinically apparent radiation retinopathy and/or radiation optic neuropathy post-brachytherapy.

MAIN OUTCOME MEASURES

The relationship of the peripapillary retinal capillary density (PPCD) as measured by OCTA to the calculated dose to the optic nerve (D50, the dose to 50% of the disc) and the LogMAR vision was evaluated.

RESULTS

No significant difference was seen in the PPCD as measured by OCTA when comparing the eye with melanoma to the fellow eye prior to brachytherapy; however the PPCD was significantly lower in treated eyes (52.9% +/- 22.4%) than in fellow eyes that did not receive radiation (73.3% +/- 13.7%, p = 0.004). There was an inverse linear correlation between D50 and the PPCD (Pearson's; r= -0.528, P=0.043) and between visual acuity and the PPCD (Pearson's; r= -0.564, P=0.028).

CONCLUSIONS

Among patients with clinically apparent radiation retinopathy and/or radiation optic neuropathy, PPCD was lower in the treated eye and correlated with the radiation dose to the optic nerve and the visual acuity. OCTA provides a measure of capillary changes following radiation, and may serve as a quantitative endpoint to address visual prognosis.

An automated framework to quantify areas of regional ischemia in retinal vascular diseases with OCT angiography

In this observational and cross-sectional study, capillary nonperfusion (CNP) and vascular changes in branch retinal vein occlusion (BRVO, sample size [n] = 26) and choroidal neovascularization (CNV, n = 29) were evaluated. Subjects underwent imaging using Optical coherence tomography angiography (Angiovue OCTA, RTVue XR, Optovue Inc., Fremont, California). Local fractal analysis was applied to the OCTA images of superficial, deep and choriocapillaris layer. CNP area (BRVO eyes) and vascular parameters were computed using local fractal-based method. Sensitivity and specificity of vascular parameters were assessed with receiver operating characteristics curve. Automated CNP area showed excellent agreement with manually quantified CNP areas in both superficial (intraclass coefficient [ICC] = 0.96) and deep (ICC = 0.96) layers. BRVO eyes showed significantly altered (P < .05) vascular parameters in both superficial and deep layer as compared to normal eyes (n = 30). CNVM eyes had significantly higher capillary free zones (P < .001) as compared to normal eyes. In normal vs BRVO eyes, vessel density and spacing between the large vessels had similar area under the curve (AUC) (P > .05) in both superficial (0.97 and 0.97, respectively) and deep layer (0.99 and 0.98, respectively). Further, capillary free zones showed high AUC (0.92) in differentiating CNV eyes from normal eyes.