QUALITATIVE AND QUANTITATIVE FOLLOW-UP USING OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF RETINAL VEIN OCCLUSION TREATED WITH ANTI-VEGF: Optical Coherence Tomography Angiography Follow-up of Retinal Vein Occlusion

Widefield, Swept-Source Optical Coherence Tomography Angiography Metrics as Predictors of Anti-VEGF Treatment in Retinal Vein Occlusions

BACKGROUND AND OBJECTIVE

Our objective was to assess baseline widefield swept-source optical coherence tomography angiography (WF SSOCTA) microvascular metrics as predictors for the number of anti-vascular endothelial growth factor (VEGF) injections and visual acuity (VA) at 12-months follow-up in patients with retinal vein occlusion (RVO).

PATIENTS AND METHODS

This was a prospective study including 49 RVO eyes from 49 patients who had not received an anti-VEGF injection for at least 3 months prior to imaging. Microvascular metrics from 6×6-mm and 12×12-mm angiograms were assessed using linear regression models, adjusting for age.

RESULTS

Reductions in the vessel density (VD) and vessel skeletonized density (VSD) vascular metrics were associated both with a higher number of anti-VEGF injections at all follow-up time points and reduced VA 12 months after imaging in all RVO eyes.

CONCLUSIONS

WF SS-OCTA VD and VSD micro-vascular metrics at baseline can prognosticate VA and number of anti-VEGF injections required at 3, 6, and 12 months in RVO eyes. [Ophthalmic Surg Lasers Imaging Retina 2024;55:374-382.].

Changes in wider field swept-source OCT angiography vascular metrics with anti-vascular endothelial growth factor therapy in central retinal vein occlusion

PURPOSE

To investigate the impact of anti-VEGF therapy on vascular metrics in eyes with macular edema secondary to central retinal vein occlusion (CRVO) using wider field swept-source OCT angiography (WF SS-OCTA).

METHODS

We included 23 eyes with macular edema associated with non-ischemic CRVO from 22 patients treated with anti-VEGF therapy (median number of injections: 5 [2-9]). Changes in vessel density (VD), vessel skeletonized density (VSD), and foveal avascular zone (FAZ) parameters were measured using WF SS-OCTA. Visual acuity (VA) and central subfield thickness (CST) were also measured.

RESULTS

Median CST decreased significantly from 369 µm (305-531) to 267 µm (243-300, p < 0.001). VD and VSD parameters in 12 × 12 mm images showed significant reductions. For instance, VSD in the whole retina decreased from a median of 13.37 (11.22-13.74) to 11.29 (9.36-12.97, p = 0.013). Additionally, a significant increase in FAZ circularity was found, suggesting improved microvascular integrity. Significant inverse correlations were found between the number of anti-VEGF injections and all VSD and VD parameters on the 12 × 12 mm images (p < 0.05). Notably, the reductions in VSD and VD on 12 × 12 mm angiograms in the deep capillary plexus (DCP) after each injection significantly correlated with increased logMAR VA (worse VA).

CONCLUSION

Anti-VEGF therapy in CRVO patients not only mitigates macular edema but also alters the overall microvascular morphology and functionality as revealed by WF SS-OCTA.

Role of optical coherence tomography angiography in the evaluation of peripheral ischemia in retinal vein occlusion

In the last decade, optical coherence tomography angiography (OCTA) has become part of the clinical management of retinal vein occlusion (RVO), proving in itself a useful technique for both the prediction of visual acuity (VA) outcomes and the risk of complications. In fact, OCTA has been proven a valid imaging technique in detailed assessment of foveal and parafoveal microvascular status in both acute and chronic RVO. Quantitative OCTA data have shown a significant correlation not only with final VA but also with the extension of peripheral ischemia, which represents a major risk factor for macular edema recurrence and neovascularization onset. Finally, wide-field OCTA represents a promising noninvasive technique for the assessment of peripheral ischemia. The aim of this review is to report the main literature findings about microvascular changes and clinical applications of OCTA in the context of RVO-induced peripheral ischemia.

An Analysis of Optical Coherence Tomography Angiography (OCT-A) Perfusion Density Maps in Patients Treated for Retinal Vein Occlusion with Intravitreal Aflibercept

AIM

The primary goal of this study was to evaluate the reduction in non-perfusion area and improvement in blood flow as well as the reduction in retinal edema on optical coherence tomography angiography (OCT-A) in patients with retinal vein occlusion treated with 2 mg intravitreal injections of aflibercept.

MATERIAL AND METHODS

Fifty eyes of nine patients with central retinal vein occlusion (CRVO) and sixteen patients with branch retinal vein occlusion (BRVO), aged 50 to 75 years, were collectively analyzed as retinal vein occlusion (RVO). The following parameters were analyzed: superficial vessel density (VDSF), deep vessel density (VDD), flow area in the outer retina (FAOR), choriocapillaris flow area (FACC), non-flow area (NFA) and the foveal avascular zone (FAZ).

RESULTS

OCT-A revealed a reduction in macular edema. The most significant change in central retinal thickness (CRT) was observed between measurement timepoint "5" and the baseline (46%). The non-flow area was also reduced. Following a significant decrease in superficial vessel density 30 days after the first dose of aflibercept, a non-significant increase was noted at the subsequent timepoints. An increase was also found in deep vessel density and choriocapillaris flow area. Improvements in the above OCT-A parameters resulted in increased retinal blood flow and improved visual acuity.

CONCLUSIONS

Patients with retinal vein occlusion treated with 2 mg aflibercept exhibited reduced macular edema and FAZ, increased vessel density, improved blood flow, and better visual acuity.

Clinical Use of Optical Coherence Tomography Angiography in Retinal Diseases

The advent of optical coherence tomography angiography (OCTA) is one of the cornerstones of fundus imaging. Essentially, its mechanism depends on the visualization of blood vessels by using the flow of erythrocytes as an intrinsic contrast agent. Although it has only recently come into clinical use, OCTA has become a non-invasive diagnostic tool for the diagnosis and follow-up of many retinal diseases, and the integration of OCTA in multimodal imaging has provided a better understanding of many retinal disorders. Here, we provide a detailed overview of the current applications of OCTA technology in the diagnosis and follow-up of various retinal disorders.

Optical Coherence Tomography Angiography in Retinal Vascular Disorders

Traditionally, abnormalities of the retinal vasculature and perfusion in retinal vascular disorders, such as diabetic retinopathy and retinal vascular occlusions, have been visualized with dye-based fluorescein angiography (FA). Optical coherence tomography angiography (OCTA) is a newer, alternative modality for imaging the retinal vasculature, which has some advantages over FA, such as its dye-free, non-invasive nature, and depth resolution. The depth resolution of OCTA allows for characterization of the retinal microvasculature in distinct anatomic layers, and commercial OCTA platforms also provide automated quantitative vascular and perfusion metrics. Quantitative and qualitative OCTA analysis in various retinal vascular disorders has facilitated the detection of pre-clinical vascular changes, greater understanding of known clinical signs, and the development of imaging biomarkers to prognosticate and guide treatment. With further technological improvements, such as a greater field of view and better image quality processing algorithms, it is likely that OCTA will play an integral role in the study and management of retinal vascular disorders. Artificial intelligence methods-in particular, deep learning-show promise in refining the insights to be gained from the use of OCTA in retinal vascular disorders. This review aims to summarize the current literature on this imaging modality in relation to common retinal vascular disorders.

Hemodynamic Effects of Anti-Vascular Endothelial Growth Factor Injections on Optical Coherence Tomography Angiography in Diabetic Macular Edema Eyes

Purpose

To evaluate retinal hemodynamic responses to anti-vascular endothelial growth factor (VEGF) injection in eyes with diabetic macular edema using optical coherence tomography angiography (OCTA). We performed a comparison of two different thresholding methods to identify the most accurate for studying the vessel density (VD) in diabetic macular edema eyes.

Methods

The study prospectively included 26 eyes of 22 subjects (aged 60.2 ± 13.7 years) who underwent OCTA scan before and after anti-VEGF injection (mean interval between OCTA = 31.1 ± 17.3 days). We analyzed adjusted flow index, VD, and Skeletonized vessel length density in the parafoveal area (3-mm annulus with a 1-mm inner circle), along with full-thickness fovea avascular zone area and central foveal thickness (CFT). Using averaged scans VD as the ground truth, we compared two different algorithms for VD at the different plexuses. Longitudinal changes were assessed using a generalized linear model correcting for central foveal thickness and Q-score.

Results

We found significantly decreased adjusted flow index in the DCP layer (P = 0.010) at the follow-up. Furthermore, foveal avascular zone (P < 0.001) and central foveal thickness (P = 0.003) showed significant decrease on follow-up compared with baseline. Comparing the thresholding algorithms showed that vessel length density-based thresholding was more accurate for quantifying the DCP VD.

Conclusions

The adjusted flow index decreased significantly in the DCP layer on follow-up OCTA scan, suggesting vascular flow disruption and decreased deep retinal perfusion after anti-VEGF injection. Our results also highlight the fact that the choice of thresholding method is particularly critical for DCP quantification in eyes with diabetic macular edema.

Translational Relevance

Findings confirmed impaired deep retinal capillary flow after anti-VEGF injection.

Comparison of Choroidal Thickness, Foveal Avascular Zone, and Macular Capillary Density in Macular Edema Secondary to Branch Retinal Vein Occlusion Treated with Ranibizumab or Aflibercept-A Prospective Study

This prospective comparative case series aims to compare best-corrected visual acuity (BCVA), retinal microvasculature, and retinal structural changes in patients treated with either ranibizumab or aflibercept for macular edema (ME) secondary to treatment-naïve branch retinal vein occlusion (BRVO) by optical coherence tomography angiography (OCTA). Ten patients were enrolled with macular capillary density of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) and foveal avascular zone (FAZ) measured in both eyes before and after treatment. Final central retinal thickness and BCVA improved significantly (p < 0.05), and densities of SCP and DCP of BRVO sectors were significantly lower at baseline than fellow eye counterparts and remained persistently lower during treatment, particularly in the aflibercept group (p < 0.05). SCP density, DCP density of both BRVO sectors (p = 0.0001, p < 0.0001), and non-BRVO sectors (p < 0.0001, p < 0.0001) were significantly correlated with final BCVA for diseased eyes. Using multivariate general linear model analysis, and including OCTA parameters only, but not all of the available clinical data, DCP density of BRVO sectors in both eyes was the most predictive factor for final visual outcome (probability p < 0.0001). OCTA offered further qualitative and quantitative evaluation of treatment-naïve BRVO. Judging by OCTA parameters, not only in the diseased eye but also in the fellow eye, DCP density of BRVO sectors was the most predictive factor of final visual outcome.

Optical Coherence Tomography Angiography In Central Retinal Vein Occlusion: Macular Changes And Their Correlation With Peripheral Nonperfusion At Ultra-Widefield Fluorescein Angiography

INTRODUCTION

To investigate the correlation between ischemic index (ISI) measured on ultra-widefield (UWF) fluorescein angiography (FA) images and macular parameters obtained by optical coherence tomography angiography (OCT-A) in eyes affected by central retinal vein occlusion (CRVO).

METHODS

Retrospective study of data from 12 eyes affected by treatment-naïve CRVO. All patients underwent a comprehensive ocular examination including structural OCT, OCT-A, and UWF FA. Variables analyzed included best-corrected visual acuity (BCVA) measured with the ETDRS chart; foveal avascular zone (FAZ) area at full-thickness OCT-A angiogram; perfusion density (PD) in the superficial (SCP) and deep capillary plexus (DCP); ISI; and central macular thickness (CMT).

RESULTS

ISI showed a significant positive correlation with FAZ area (r=0.63, p=0.019) and a significant negative correlation with PD in the SCP (r=-0.62, p=0.022), PD in the DCP (r=-0.66, p=0.011), and BCVA (r=-0.75, p=0.002). FAZ area also negatively correlated to PD in the SCP (r=-0.75, p=0.002) and DCP (r=-0.64, p=0.016). BCVA positively correlated to PD in the SCP (r=0.67, p=0.009) and DCP (r=0.68, p=0.008), while a negative correlation was found with FAZ area (r=-0.65, p=0.013) and CMT (r=-0.70, p=0.006).

DISCUSSION/CONCLUSION

OCT-A macular parameters (namely, FAZ area and PD of SCP and DCP) significantly correlated with ISI, a quantitative way to assess peripheral retinal nonperfusion on UWF FA. Macular OCT-A analysis may help in assessing the need for additional UWF FA testing in eyes affected by CRVO.

Changes in Macular Microvascular Structure in Macular Edema Secondary to Branch Retinal Vein Occlusion Treated with Antivascular Endothelial Growth Factor for One Year

Purpose

To observe the changes in macular microvascular structure and the correlation between anatomy and visual function in patients with macular edema secondary to branch retinal vein occlusion (BRVO) treated with antivascular endothelial growth factor for one year.

Methods

This prospective study enrolled 39 patients (one eye per patient) who received intravitreal injections of ranibizumab for macular edema secondary to BRVO. All patients received a minimum of 3 initial monthly ranibizumab injections and criteria-driven pro re nata (PRN) dosing thereafter for visual acuity (VA) and central retinal thickness (CRT) stabilization. The follow-up period of this study was one year. The vascular density (VD) of the superficial retinal capillary plexus (SCP) and deep retinal capillary plexus (DCP), the foveal avascular zone (FAZ) area, the FAZ perimeter, the VD within a 300 μm wide ring surrounding the FAZ (FD-300), and the acircularity index (AI) were measured automatically by optical coherence tomography angiography (OCTA) at baseline, month 6, and month 12.

Results

Compared with those before treatment, the VD of the SCP significantly decreased 6 months after treatment (P < 0.05), while the area and perimeter of the FAZ increased significantly (P < 0.01). After 12 months of treatment, the area and perimeter of the FAZ increased significantly (P < 0.01). There was no significant difference in any parameters between 12 months and 6 months after treatment (P > 0.05). The change in BCVA was negatively correlated with the VD of the SCP at 12 months (P=0.0447, r = -0.3233). There was a relationship between the DBP and AI, and CRT was related to VD of DCP at baseline (P=0.028,  0.0209; r = 0.383, -0.384). The PERIM and AI at 12 months were significantly associated with the recurrence of macular edema, and the changes in vascular density in the SCP and PERIM were significantly associated with the number of injections within 12 months (P < 0.05).

Conclusions

One year after ranibizumab treatment, the area and perimeter of the FAZ were enlarged, while the VD of the SCP and DCP remained stable, which indicated that ranibizumab treatment did not improve macular blood supply and macular ischemia in BRVO patients.

Macular Microvascular Changes and Their Correlation With Peripheral Nonperfusion in Branch Retinal Vein Occlusion

PURPOSE

To investigate the correlation between macular microvascular alterations on optical coherence tomography angiography (OCTA) and retinal ischemia on ultra-widefield fluorescein angiography (UWF FA) in eyes with branch retinal vein occlusion (BRVO).

DESIGN

Cross-sectional study.

METHODS

This prospective study was performed from September 2019 to June 2020 at Yeungnam University Medical Center. We included 60 patients with treatment-naïve BRVO. Two independent, masked graders analyzed OCTA parameters, including vessel density, skeletal density, and fractal dimension (FD), and UWF FA parameters, including retinal nonperfusion area (NPA) and ischemic index (ISI), from various concentric regions (perimacular region, 0.5-3 mm radius; near-peripheral region, 3-10 mm; midperipheral region, 10-15 mm; far-peripheral region, >15 mm). A repeated-measures analysis of variance test and a paired t test were performed for inter-visit and inter-regional comparisons, and Pearson correlation coefficient and multivariate regression analyses were performed to examine the correlation between UWF FA and OCTA parameters.

RESULTS

The OCTA parameters from both the superficial and deep capillary plexuses (DCP) were significantly correlated with NPA and ISI in all concentric regions. Even after adjusting for several covariates, all OCTA parameters revealed a significant association with ISI on UWF FA. Moreover, OCTA parameters from DCP were significantly correlated with concentrations of placental growth factor and vascular endothelial growth factor. Although all OCTA parameters achieved excellent results of area under the curve (AUC) > 0.9 for detecting severe retinal ischemia, defined as ISI >10%, FD reduction in DCP was the most reliable parameter (AUC = 0.948, P < .001), and 5.39% was the best cut-off point for predicting ISI > 10%.

CONCLUSIONS

OCTA is a useful noninvasive tool not only for evaluation of macular microvasculature but for supposition of peripheral nonperfusion in eyes with BRVO.

Correlation between the Nonperfusion Area on Ultra-Widefield Fluorescein Angiography and Nonflow Area on Optical Coherence Tomographic Angiography in Retinal Vein Occlusion

Aims

To compare the relationship between the nonperfusion area (NPA) on ultra-widefield fluorescein angiography (UWFFA) and the nonflow area (NFA) on optical coherence tomographic angiography (OCTA) in retinal vein occlusion (RVO).

Methods

Cross-sectional study. 46 eyes of 46 RVO patients who underwent UWFFA and OCTA. NPA and ischemic index (ISI) were quantified on UWWFA. NFA, vessel density (VD) of the superficial capillary plexus (SCP), the deep capillary plexus (DCP), and the size foveal avascular zone (FAZ) on 3 ∗ 3 mm OCTA were measured. The association of the NPA and ISI on UWWFA and the parameters on OCTA were analyzed. Spearman correlation was used for statistical testing.

Results

The NPA and ISI on UWFFA were significantly correlated with the NFA on OCTA in RVO, and r values were 0.688 (p < 0.01) and 0.680 (p < 0.01), respectively. VD in the SCP of the temporal quadrant was negatively correlated with NPA and ISI, and r values were -0.346 (p < 0.05) and -0.337 (p < 0.05), respectively. VD in the DCP of the temporal quadrant was negatively correlated with the NPA, and the r value was -0.246 (p < 0.05). No significant correlation was found between the NPA and ISI on UWFFA and VD of other quadrants in the SCP or DCP and the FAZ area on OCTA.

Conclusion

NPA in the peripheral retina was correlated with NFA in macula. NFA detected by OCTA could be an indicator of the ischemic status in RVO.

The Structural and Comparative Analysis of Intravitreal Dexamethasone Implant (Ozurdex) and Anti-VEGF Injection in Branched Retinal Vein Occlusion Patients by Optical Coherence Tomography Angiography Images Quantitation

Background and Objective: To evaluate and compare the structural changes of retinal vasculature after intravitreal dexamethasone implant (Ozurdex) insertion and antivascular endothelial growth factor (anti-VEGF) injection in patients with branched retinal vein occlusion (BRVO) using optical coherence tomography angiography (OCTA).Study Design/Materials and Methods: We retrospectively analyzed 39 patients with unilateral BRVO. Subjects were divided into two groups according to treatment agent: Ozurdex (n = 18) and anti-VEGF (n = 21). Swept Source (SS) OCT and OCTA were performed and images were analyzed quantitatively using ImageJ (National Institutes of Health) software. Intravitreal implant and anti-VEGF injections were performed following a prn regimen. The specific anti-VEGF agent used was chosen among bevacizumab, ranibizumab and aflibercept.Results: Of the 39 patients (mean ± SD age, 70.0 ± 8.9 years [range, 48-89 years]; 20 men [51.0%]) with unilateral BRVO, in an independent two-sample t test, there was greater vascular reperfusion of the choriocapillaris slab in the intravitreal Ozurdex implant group than in the anti-VEGF group using the angiography mode (P = .013). Increased number of particles was more prominent in intravitreal anti-VEGF injection group than intravitreal Ozurdex implant group in outer retina slab of En-face mode (P = .039). There was no statistically significant difference between the 2 treatment groups in relation to the Early Treatment Diabetic Retinopathy Study (ETDRS) density map and other angiography slabs; and the superficial, deep, and outer retina.Conclusions: Results of a quantitative analysis of OCTA images using ImageJ software suggest that the intravitreal Ozurdex implant induced increased retinal vascular perfusion compared with anti-VEGF injection for the treatment of BRVO.

Microvascular comparison in younger and older patients with retinal vein occlusion analyzed by OCT angiography

Background

To compare changes in retinal microvasculature of young and elderly patients with retinal vein occlusion (RVO) after anti-VEGF treatment.

Methods

RVO patients who underwent anti-VEGF treatment were retrospectively reviewed and categorized into two groups based on age. The OCT angiography images were obtained during each visit. Best corrected visual acuity (BCVA), vessel density (VD) and foveal avascular zone (FAZ) were measured and compared between the two groups. Vision improvements and retinal microvasculature changes were also correlated.

Results

Twenty patients with 20 eyes were enrolled in the younger group and 46 patients with 46 eyes were enrolled in the older group. Younger patients demonstrated better BCVA, higher VD and smaller FAZ than older patients at 12 months after the first anti-VEGF treatment. The improvement of VD was observed only in the younger group. A positive correlation between vision improvement and VD increase was noted.

Conclusions

Young patients with RVO can achieve rapid rehabilitation of deep retinal vasculature which lead to a better visual outcome.

Optical coherence tomography angiography and Humphrey field analyser for macular capillary non-perfusion evaluation in branch retinal vein occlusion

We non-invasively evaluated macular non-perfused areas (m-NPAs) of branch retinal vein occlusion (BRVO) using optical coherence tomography (OCT) angiography and the Humphrey visual field analyser 10-2 programme (HFA 10-2). We enrolled 30 patients (30 eyes) with macular oedema secondary to BRVO. OCT angiography was used to photograph the macula at 6 × 6-mm; sizes of m-NPAs in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were measured in four areas. For HFA 10-2, we divided the actual measurement threshold of 68 points into four areas and calculated the mean central visual field sensitivity (CVFS). The correlation between the mean m-NPA and mean CVFS (dB) in each area was examined. There was a strong correlation between the m-NPA of each region detected in SCP and DCP, and the mean CVFS of each corresponding area (SCP: r = − 0.83, r = − 0.64, r = − 0.73, and r = − 0.79; DCP: r = − 0.82, r = − 0.71, r = − 0.71, and r = − 0.70), p values were < 0.001 for all. m-NPAs were associated with decreased visual field sensitivity in BRVO. Non-invasive m-NPA evaluation was possible using OCT angiography and HFA 10-2.

Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography

BACKGROUND

To evaluate the reliability of foveal avascular zone (FAZ) area measurements using optical coherence tomography angiography (OCTA) in eyes with retinal vein occlusion (RVO).

METHODS

Twenty-five OCTA exams of patients with RVO were evaluated retrospectively. Three examiners performed manual measurements of the FAZ, and interrater and intrarater reliability were obtained.

RESULTS

The intraclass correlation coefficient (ICC) for interrater reliability for individual measurements was 0.62 (moderate) with a 95% confidence interval (CI) of 0.40 to 0.79 (p < 0.001). The ICC (95% CI) for intrarater reliability was 0.92 (0.82 to 0.96) for rater A, 0.96 (0.91 to 0.98) for B, and 0.88 (0.76 to 0.94) for C (p < 0.001). In all subanalyses including presence of edema and type of occlusion, interrater reliability was poor/moderate, and intrarater reliability was good/excellent.

CONCLUSION

The FAZ varies significantly among eyes with RVO, so measurements obtained using OCTA should be analyzed with caution due to the moderate level of reliability among different examiners.

Angiographic Risk Features of Branch Retinal Vein Occlusion Onset as Determined by Optical Coherence Tomography Angiography

Purpose

Examine associations between the vasculature at arteriovenous (AV) crossings and the onset of branch retinal vein occlusion (BRVO).

Methods

We included 78 patients with major BRVO, 35 patients with macular BRVO, and 110 controls without BRVO and determined the vessel positions at AV crossings, where the first- or second-order branches of the retinal veins associate, using a viewing angle of 12 × 12 mm² in optical coherence tomography angiography (OCTA).

Results

We reviewed 1349 and 1276 AV crossings in BRVO patients and control subjects, respectively. The proportions of venous overcrossing were 26.5%, 28.6%, and 26.8% at non-causative crossings in BRVO eyes, non-BRVO fellow eyes, and unaffected control eyes, respectively; however, the rate of venous overcrossings at the causative crossings was 45.1%. In OCTA analyses, we divided the branches into macular- or non-macular veins. The rate of venous overcrossing was 52.5% at causative crossings in major BRVO but was 28.6% in macular BRVO. Odds ratios for whether venous overcrossing was a risk factor for BRVO were 3.09 (95% confidence interval [CI], 1.96–4.88) and 0.94 (95% CI, 0.44–2.00) for non-macular veins and macular veins, respectively. The patients with major BRVO caused by venous overcrossing were younger than patients for whom the cause was arterial overcrossing (P < 0.001). The onset of macular BRVO did not differ between crossing patterns at causative crossings (P = 0.60).

Conclusions

In eyes with BRVO, venous overcrossing was a common angiographic feature at causative crossings and might be a risk factor for major BRVO onset.

Clinical validation of the RTVue optical coherence tomography angiography image quality indicators

IMPORTANCE

All automated image quality indicators for en face optical coherence tomography angiography (OCTA) images require gold standard validation for determining optimum thresholds.

BACKGROUND

A manual grading system (gold standard) for OCTA images was validated and compared to two automated image quality indicators: signal strength index (SSI) and scan quality index (SQI) generated by different software versions of the Optovue OCTA device.

DESIGN

Retrospective cross-sectional study.

PARTICIPANTS

A total of 52 eyes of 52 healthy individual and 77 eyes of 51 patients with retinal vascular diseases.

METHODS

A total of 129 OCTA images of the superficial vascular plexus were graded manually by three independent examiners. Each image was assigned grades 1 to 4 (1-2, unacceptable; 3-4, acceptable) masked to the software-generated quality indicators.

MAIN OUTCOME MEASURES

Inter-grader agreement and comparison of the utility of SSI and SQI in discriminating between acceptable and unacceptable OCTA images.

RESULTS

There was a substantial agreement between the three graders (κ = 0.63). Mean SSI and SQI was significantly different between acceptable and unacceptable images (P < .001). SQI outperformed SSI in separating acceptable from unacceptable images (areas under the receiver operating characteristic curve: 0.87 vs 0.80) and the optimum cut-off was ≥7 for SQI and ≥70 for SSI for acceptable images. Up to 30% of images with quality indicators reaching the optimum SQI and SSI cut-off thresholds still had unacceptable quality on manual grading. Unacceptable images were found in 33% and 66% of healthy and diseased eyes, respectively.

CONCLUSIONS AND RELEVANCE

SQI is closely related to manual grading but we caution reliance on the optimized threshold to determine image quality. SQI is superior to SSI in discriminating between acceptable and unacceptable images.

Papillary Vessel Density Changes After Intravitreal Anti-VEGF Injections in Hypertensive Patients with Central Retinal Vein Occlusion: An Angio-OCT Study

PURPOSE

To investigate papillary microvascular changes in patients affected by macular edema due to Central Retinal Vein Occlusions (CRVO) after anti-Vascular Endothelial Growth Factor (VEGF) therapy.

METHODS

Prospective analysis of papillary and peripapillary vessel density (VD) changes in 18 eyes of 18 hypertensive patients affected by CRVO before and after the loading-phase of intravitreal Ranibizumab (IVR) injections. Data were quantitatively measured by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) before as well as 1 month and 4 months after injections. The correlation between post-treatment best-corrected visual acuity (BCVA) and changes in the retinal microvasculature evaluated by OCTA was assessed. Results: 18 eyes of 18 consecutive patients with a known history of arterial hypertension and affected by an acute CRVO episode were enrolled. Central macular thickness (CMT) was significantly reduced after IVR injections (p < 0.001), while mean BCVA improved from 0.70 ± 0.26 logarithm of the minimal angle of resolution (logMAR) units at baseline to 0.25 ± 0.18 logMAR units after 4 months (p < 0.001). VD inside disc and peripapillary significantly increased (p < 0.001 and p = 0.01, respectively) after treatment.

CONCLUSIONS

OCTA showed VD increase in the papillary area in patients affected by CRVO after anti-VEGF therapy. This area could represent a new region of interest to study microvasculature changes concomitant with severe macular edema.

A Novel Automatic Method to Estimate Visual Acuity and Analyze the Retinal Vasculature in Retinal Vein Occlusion Using Swept Source Optical Coherence Tomography Angiography

The assessment of vascular biomarkers and their correlation with visual acuity is one of the most important issues in the diagnosis and follow-up of retinal vein occlusions (RVOs). The high workloads of clinical practice make it necessary to have a fast, objective, and automatic method to analyze image features and correlate them with visual function. The aim of this study is to propose a fully automatic system which is capable of estimating visual acuity (VA) in RVO eyes, based only on information obtained from macular optical coherence tomography angiography (OCTA) images. We also propose an automatic methodology to rapidly measure the foveal avascular zone (FAZ) area and the vascular density (VD) in the superficial and deep capillary plexuses in swept-source OCTA images centered on the fovea. The proposed methodology is validated using a representative sample of 133 visits of 50 RVO patients. Our methodology estimates VA with very high precision and is even more accurate when we integrate depth information, providing a high correlation index of 0.869 with the real VA, which outperforms the correlation index of 0.855 obtained when estimating VA from the data obtained by the semiautomatic existing method. In conclusion, the proposed method is the first computational system able to estimate VA in RVO, with the additional benefits of being automatic, less time-consuming, objective and more accurate. Furthermore, the proposed method is able to integrate depth information, a feature which is lacking in the existing method.

Arteriovenous crossing associated with branch retinal vein occlusion

Branch retinal vein occlusion (BRVO) is defined as the focal occlusion of a first or second-order branch of retinal vein, which occurs most frequently at an arteriovenous (AV) crossing. Direct ophthalmoscopy, color fundus photography, and fluorescein angiography facilitate observation of AV crossings parallel to the retinal plane. Optical coherence tomography (OCT), with its high-depth resolution, enables observation of retinal lesions perpendicular to the retinal plane. OCT angiography (OCTA) provides depth-resolved images of the retinal vasculature by segmenting three-dimensional data. In this review, we discuss novel findings related to affected AV crossings associated with BRVO obtained via OCT and OCTA. The high-depth resolution of OCT or OCTA is useful for observation of the narrowed vein and determination of the vessel position of the affected AV crossing. Studies using OCT and OCTA have shown that BRVO caused by a venous overcrossing is more prevalent than previously reported, and that venous narrowing was significantly greater in instances caused by a venous overcrossing than in those caused by an arterial overcrossing. Moreover, OCTA also revealed that the retinal nonperfusion area size was larger in eyes with BRVO caused by a venous overcrossing than in those with BRVO caused by an arterial overcrossing. This contrasts with earlier findings obtained by conventional imaging modalities predating OCT, which showed that an arterial overcrossing was more common than a venous overcrossing at the causative venous occlusion site in eyes with BRVO. This review discusses these findings and their significance in the study of AV crossing associated with BRVO.

Changes in Peripapillary Microvasculature and Retinal Thickness in the Fellow Eyes of Patients With Unilateral Retinal Vein Occlusion: An OCTA Study

Purpose

To evaluate changes in peripapillary microvascular parameters in the fellow eyes of patients with unilateral retinal vein occlusion (RVO) using optical coherence tomography angiography (OCTA) and to determine the relationships between peripapillary microvasculature and retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL) thickness.

Methods

Eighty-three patients with unilateral RVO (50 patients with branch RVO and 33 with central RVO) and 83 normal controls were enrolled. OCTA (Cirrus HD-OCT 5000 with AngioPlex) 6 × 6-mm scans centered on the optic disc were acquired. Peripapillary vessel density (VD) and perfusion density (PD) were automatically calculated.

Results

The average RNFL and GC-IPL thicknesses in the fellow eyes of RVO patients were significantly thinner than in normal controls (93.5 vs. 96.6 μm, P = 0.013 and 81.3 vs. 84.1 μm, P = 0.003, respectively). In the fellow eyes of patients with unilateral RVO, the peripapillary VD of the inner ring, outer ring, and full area (17.47, 18.50, and 17.89, respectively) were significantly lower than those of controls (17.87, 18.87, and 18.27, respectively). The peripapillary PD of the inner ring, outer ring, and full area (0.456, 0.467, and 0.456, respectively) were also significantly lower than those of controls (0.468, 0.476, and 0.466, respectively). RNFL and GC-IPL thicknesses were correlated with both peripapillary VD and PD.

Conclusions

OCTA revealed that peripapillary microvascular parameters in the fellow eyes of patients with unilateral RVO were decreased, and GC-IPL and RNFL thinning were also observed. The RNFL and GC-IPL thicknesses were positively correlated with both peripapillary VD and PD.

Segmentation of the Four-Layered Retinal Vasculature Using High-Resolution Optical Coherence Tomography Angiography Reveals the Microcirculation Unit

Purpose

To differentiate the four layers of the retinal vessel network in the human macula and examine their morphologic features using high-resolution optical coherence tomography angiography (HR-OCTA).

Methods

Macular areas measuring 464 × 464 pixels of 10 right eyes of 10 healthy subjects without ocular disease were scanned 10 times using a HR-OCTA device. Averaged OCTA images were created. Based on clear decorrelation signals, four vascular slabs were segmented, comprising one each in the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and top and bottom of the inner nuclear layer (INL). Qualitative features and quantitative measurements in each slab were compared with those in conventionally segmented slabs.

Results

HR-OCTA isolated four layers of vascular plexuses in the macula that followed the corresponding anatomic layers. Segmentations for the RNFL revealed that radial peripapillary capillaries (RPCs) extended to the central macular area. The RPCs followed relatively straight and long paths, with few apparent feed points and anastomoses. The GCL slab enhanced visualization of the capillary-free zones around the arteries and arterioles and helped to differentiate arterial and venous systems. The arterioles and venules were linked by capillaries that were arranged in a mesh-like fashion, with multiple arteriolar feed points and anastomoses. Vascular plexuses in the top and bottom of the INL consisted of capillaries in a vortex arrangement. The center of these vortex arrangements was consistent with the venules in the GCL.

Conclusions

HR-OCTA can differentiate the four layers of vascular plexuses in the human macula and elucidate their angiographic features.

Quantitative Analysis of Retinal Microvascular Changes after Conbercept Therapy in Branch Retinal Vein Occlusion Using Optical Coherence Tomography Angiography

PURPOSE

To quantitatively evaluate microvascular changes in eyes with macular oedema due to branch retinal vein occlusion (BRVO) using optical coherence tomography angiography (OCTA) before and after intravitreal conbercept injection and the correlation of such changes with best-corrected visual acuity (BCVA) and retinal thickness.

METHODS

Twenty-eight eyes of 28 patients treated with a single intravitreal injection of conbercept for macular oedema due to BRVO were included in this study. The automatically measured values of the vessel density in the superficial (SCP) and deep retinal capillary plexus (DCP), the foveal avascular zone (FAZ) area, the FAZ perimeter, the vessel density within a 300 μm wide ring surrounding the FAZ (FD-300), the acircularity index (AI), the choriocapillaris flow area and the retinal thickness were obtained via OCTA before and at 1 month after initial injection and compared with those of age- and sex- matched healthy subjects.

RESULTS

In BRVO eyes, the vascular density in the SCP and DCP, the FD-300 and the flow area of choriocapillaris were significantly lower than those in healthy eyes, while the AI and the retinal thickness were significantly increased. After treatment, the retinal thickness in eyes with BRVO was significantly decreased in all quadrants, and the mean BCVA dramatically increased from 20/162 to 20/78 (p = 0.0017). The mean flow area of choriocapillaris significantly improved after treatment. Moreover, negative correlations between the logMAR BCVA and the whole vascular density in the SCP and DCP as well as the flow area of choriocapillaris were observed.

CONCLUSION

OCTA enables non-invasive, layer-specific and quantitative assessment of microvascular changes in eyes with BRVO before and after treatment, and it can be used as a valuable imaging tool for the evaluation of the follow-up in BRVO patients.

Microvascular changes after conbercept therapy in central retinal vein occlusion analyzed by optical coherence tomography angiography

AIM

To investigate microvascular changes in eyes with central retinal vein occlusion (CRVO) complicated by macular edema before and after intravitreal conbercept injection and evaluate correlations between these changes and best-corrected visual acuity (BCVA) and retinal thickness.

METHODS

Twenty-eight eyes of 28 patients with macular edema caused by CRVO were included in this retrospective study. All patients received a single intravitreal conbercept injection to treat macular edema. BCVA and the results of optical coherence tomography angiography (OCTA) automatic measurements of the vessel density in the superficial (SCP) and deep retinal capillary plexus (DCP), the foveal avascular zone (FAZ) area, the FAZ perimeter (PERIM), the vessel density within a 300-µm wide ring surrounding the FAZ (FD-300), the acircularity index (AI), the choriocapillaris flow area, and retinal thickness were recorded before and at one month after treatment and compared with the results observed in age- and sex-matched healthy subjects.

RESULTS

The vessel density in the SCP and DCP, the FD-300, and the flow area of the choriocapillaris were all significantly lower in CRVO eyes than in healthy eyes, while the AI and retinal thickness were significantly higher (all P<0.05). After treatment, retinal thickness was significantly decreased, and the mean BCVA had markedly improved from 20/167 to 20/65 (P=0.0092). The flow area of the choriocapillaris was also significantly improved, which may result from the reduction of shadowing effect caused by the attenuation of macular edema. However, there were no significant changes in SCP and DCP vessel density after treatment. The flow area of the choriocapillaris at baseline was negatively correlated with retinal thickness.

CONCLUSION

OCTA enables the non-invasive, layer-specific and quantitative assessment of microvascular changes both before and after treatment, and can therefore be used as a valuable imaging tool for the evaluation of the follow-up in CRVO patients.

Branch Retinal Vein Occlusion: Treatment Outcomes According to the Retinal Nonperfusion Area, Clinical Subtype, and Crossing Pattern

This prospective study examined 58 eyes with branch retinal vein occlusion (BRVO) to investigate the effects of the nonperfusion area (NPA), clinical subtype, and crossing pattern on the 2-year outcomes of ranibizumab therapy for the macular edema (ME). All eyes received three initial monthly injections, followed by additional pro re nata (PRN) injections. The final best corrected visual acuity (BCVA) and ranibizumab injection number were not associated with the macular NPA or total NPA at baseline or month 12, and they showed no significant differences between the clinical subtypes. However, the incidence of neovascular changes was higher in the major BRVO group than in the macular BRVO group (P = 0.030). Twelve and 19 of the 34 eyes with major BRVO exhibited arterial overcrossing and venous overcrossing, respectively. At baseline, the total NPA did not differ according to the crossing pattern, however, the total NPA was significantly larger in the venous overcrossing group at month 12 (P = 0.047). At month 24, the incidence of neovascular changes was higher in the venous overcrossing group (P = 0.030). Following ranibizumab therapy for BRVO-associated ME, the clinical subtype and the arteriovenous crossing pattern may be associated with neovascular changes.

An overview of optical coherence tomography angiography and the posterior pole

Optical coherence tomography angiography is a relatively new, noninvasive technology that has revolutionized imaging of the retinal and choroidal microvasculature. This technology is based on the detection of movement or changes that represent moving red cells in sequential optical coherence tomography scans. As with other established imaging technologies, it has unique benefits as well as certain disadvantages, which include a limited field of view and vulnerability to imaging artifacts. However, software and hardware improvements are continually evolving to mitigate these limitations. Optical coherence tomography angiography has been used to gain a better understanding of microvascular changes across a spectrum of ocular diseases including diabetic retinopathy, age-related macular degeneration, glaucoma, and retinal vein occlusions. In this article, we review algorithms and techniques commonly utilized in optical coherence tomography angiography systems and compare optical coherence tomography angiography to fluorescein angiography, the current gold standard for imaging the retinal vasculature. In addition, we provide an overview of important optical coherence tomography angiography findings in a variety of ocular diseases. Although the clinical role of this technology is still poorly defined, optical coherence tomography angiography has the potential to become an invaluable tool in the diagnosis and monitoring of vascular pathologies.

Changes in Retinal Microvasculature and Visual Acuity After Antivascular Endothelial Growth Factor Therapy in Retinal Vein Occlusion

Purpose

To investigate the changes in the retinal microvasculature during the course of anti-VEGF therapy in eyes with macular edema due to retinal vein occlusion (RVO) and their association with visual outcomes.

Methods

The vessel density (VD) and foveal avascular zone (FAZ) area in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were quantitatively measured by optical coherence tomography angiography (OCTA) in 48 consecutive eyes with RVO before and 1, 3, 6, 9, and 12 months after anti-VEGF therapy. Anti-VEGF therapy was performed either with ranibizumab or aflibercept following a pro re nata (PRN) regimen. The correlation between post-treatment best-corrected visual acuity (BCVA) and changes in the retinal microvasculature evaluated by OCTA were assessed.

Results

The BCVA improved significantly at 12 months (P < 0.001). Better BCVA at 12 months was significantly associated with a better VD in the SCP and DCP both at baseline (R2 = 0.524, P < 0.001 and R2 = 0.457, P < 0.001, respectively) and at 12 months (R2 = 0.521, P < 0.001 and R2 = 0.662, P < 0.001, respectively). Overall, both VD and FAZ did not change significantly during the 12 months. However, the progression of nonperfusion was observed in the SCP in 6 (13%) eyes and in the DCP in 10 (21%) eyes. The number of macular edema recurrence was significantly associated with a decrease in the VD (P = 0.006 [SCP] and P < 0.001 [DCP]) and less visual gain (P = 0.02) after treatment.

Conclusions

Anti-VEGF therapy maintains retinal perfusion in most patients with RVO. Preserving retinal perfusion is crucial for better visual outcomes.

Macular vessel reduction as predictor for recurrence of macular oedema requiring repeat intravitreal ranibizumab injection in eyes with branch retinal vein occlusion

AIM

To determine whether there are factors that can predict the frequency of recurrences of macular oedema associated with branch retinal vein occlusion (BRVO).

METHODS

We reviewed the medical records of 31 eyes with treatment-naïve macular oedema associated with BRVO. All eyes received an intravitreal ranibizumab (IVR) injection and were followed with a pro re nata protocol for at least 12 months. A reinjection of ranibizmab was performed when the central foveal thickness was ≥300 µm. At 1 month after IVR injection, the macular vessel reduction was calculated by comparing the vessel density in the optical coherence tomography angiography in the BRVO involved half to that in the non-involved half.

RESULTS

The mean visual acuity improved from 0.35±0.27 logarithm of the minimal angle of resolution (logMAR) units (20/45; Snellen) at initial visit to 0.06±0.15 logMAR units (20/23) at 12 months (p<0.0001). During 12 months, the mean number of IVR injections was 3.8±1.8. Multivariate regression analysis showed that a greater macular vessel reduction at 1 month after initial IVR injection was significantly a negative predictor of frequency of IVR injections (β=-0.5065, p=0.0082). The visual acuity and the central foveal thickness at the initial visit or at 1 month after initial IVR injection were not predictive factors for frequency of IVR injections.

CONCLUSIONS

Patients with BRVO with a large macular vessel reduction at 1 month after an initial IVR injection have fewer recurrences and thus lower frequency of IVR injections during 12 months.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN RETINAL VEIN OCCLUSION: Correlations Between Macular Vascular Density, Visual Acuity, and Peripheral Nonperfusion Area on Fluorescein Angiography

Optical coherence tomography angiography is a noninvasive examination, which allowed automated measurements of vascular density at the level of the superficial and deep capillary plexus. Correlations were found in patients with retinal vein occlusion between the automatically quantified macular vascular densities obtained using optical coherence tomography angiography and the data obtained from conventional examination, particularly visual acuity and peripheral retinal nonperfusion assessed using fluorescein angiography.

Purpose:

To study correlations in patients with retinal vein occlusion between the automatically quantified macular vascular densities in the superficial and deep capillary plexus (DCP) obtained using optical coherence tomography angiography (OCTA) and the data from conventional examination, particularly visual acuity and peripheral retinal nonperfusion assessed using fluorescein angiography (FA).

Methods:

Retrospective, observational study of patients with retinal vein occlusion who underwent a comprehensive ophthalmic examination including FA and OCTA using the AngioVue OCTA system version 2015.100.0.35 (OptovueRTVue XR 100; AVANTI, Inc, Fremont, CA). Vascular densities in the superficial capillary plexus and DCP, as well as the area of the foveal avascular zone, were measured using the AngioAnalytics software.

Results:

Our study of 65 eyes of 61 patients (33 men, mean age: 67 years) showed a significant correlation between peripheral nonperfusion on FA and (1) automatically quantified global vascular density in both plexus (P = 0.021 for the DCP) and (2) foveal avascular zone area (P = 0.037). We also found significant correlations between capillary dropouts in both plexus and peripheral nonperfusion (P < 0.001 for both) and between visual acuity and vascular densities (P = 0.002 for the global density in the DCP). Global density less than 46% in the DCP was associated to the presence of peripheral nonperfusion area on FA (P = 0.003) and to enlargement of the superficial foveal avascular zone (P = 0.002).

Conclusion:

Our study demonstrated a significant correlation between automatically quantified macular vascular density on OCTA and peripheral nonperfusion on FA; OCTA could help identify high-risk retinal vein occlusion patients who may benefit from further evaluation using FA.

Optical Coherence Tomography Angiography in Eyes with Retinal Vein Occlusion

Optical coherence angiography (OCTA) is a noninvasive technique that has been introduced in recent years to detect ophthalmological pathology. The growing usage of OCTA to detect retinal abnormalities can be attributed to its advantages over the reference-standard fluorescein angiography (FA), although both of these techniques can be used in association. OCTA's advantages include its dye independency, its ability to produce depth-resolved images of retinal and choroidal vessels that yield images of different vascular layers of the retina, and the better delineation of the foveal avascular zone. OCTA's disadvantages include the lack of normalized patient data, artefactual projection issues, and its inability to detect low-flow lesions or pathologic conditions. Different OCTA platforms use unique algorithms to detect microvasculature, which are implemented in both spectral-domain (SD) and swept-source (SS) OCT machines. Microvascular changes in retinal vein occlusions (RVOs) are visible in both the superficial and deep capillary networks of the retina in OCTA. These visualizations include a decrease in foveal and parafoveal vascular densities, non-perfusion areas, capillary engorgement and telangiectasias, vascular tortuosity, microaneurysms, disruption of the foveal perivascular plexus, and formation of collateral vessels. The restricted field of view and inability to show leakage are important limitations associated with the use of OCTA in RVO cases. In this article, we present a brief overview of OCTA and a review of the changes detectable in different slabs by OCTA in RVO cases published in PubMed and Embase.

Relationship between Optical Intensity on Optical Coherence Tomography and Retinal Ischemia in Branch Retinal Vein Occlusion

Branch retinal vein occlusion (BRVO) may be complicated with retinal ischemia in some cases. The purpose of the current study is to investigate the relationship between optical intensity on optical coherence tomography (OCT) and retinal ischemia in BRVO. Twenty-seven eyes diagnosed with BRVO without macular edema were classified into two groups based on the presence or absence of retinal ischemia. The optical intensity of inner retinal layers and photoreceptor inner segment ellipsoid zone/retinal pigment epithelium layer (ISe/RPE) in the affected and unaffected regions were measured on OCT. Their ratio (Optical intensity ratio, OIR) was calculated and compared between affected and unaffected region. In the retinal ischemia group, the optical intensity of inner retinal layers was higher in the affected region compared to the unaffected region while the optical intensity of ISe/RPE was low. The OIR was significantly higher in the affected region compared to control (0.83 ± 0.17 vs 0.68 ± 0.09, p < 0.001). However, in the non-ischemic group, there was no significant difference between the affected and unaffected region. The BCVA was moderately correlated with OIR of affected region (r = 0.489, p = 0.010). Our study suggests that optical intensity ratio on OCT is correlated with retinal ischemia in BRVO.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

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.

An overview of the clinical applications of optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) has emerged as a novel, non-invasive imaging modality that allows the detailed study of flow within the vascular structures of the eye. Compared to conventional dye angiography, OCTA can produce more detailed, higher resolution images of the vasculature without the added risk of dye injection. In our review, we discuss the advantages and disadvantages of this new technology in comparison to conventional dye angiography. We provide an overview of the current OCTA technology available, compare the various commercial OCTA machines technical specifications and discuss some future software improvements. An approach to the interpretation of OCTA images by correlating images to other multimodal imaging with attention to identifying potential artefacts will be outlined and may be useful to ophthalmologists, particularly those who are currently still unfamiliar with this new technology. This review is based on a search of peer-reviewed published papers relevant to OCTA according to our current knowledge, up to January 2017, available on the PubMed database. Currently, many of the published studies have focused on OCTA imaging of the retina, in particular, the use of OCTA in the diagnosis and management of common retinal diseases such as age-related macular degeneration and retinal vascular diseases. In addition, we describe clinical applications for OCTA imaging in inflammatory diseases, optic nerve diseases and anterior segment diseases. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical applications of this imaging technology.

Morphologic and Functional Retinal Vessel Changes in Branch Retinal Vein Occlusion: An Optical Coherence Tomography Angiography Study

PURPOSE

The present study aimed to investigate the morphology of the retinal vasculature in eyes with branch retinal vein occlusion (BRVO) using optical coherence tomography (OCT) angiography.

DESIGN

Observational case series.

METHODS

Fluorescein angiography (FA) and OCT angiography were used to examine macular area and the retinal vasculature at the affected arteriovenous (AV) crossing in 46 patients with BRVO.

RESULTS

FA revealed that the affected AV crossing pattern involved arterial overcrossing in 23 eyes (50.0%) and venous overcrossing in 11 eyes (23.9%). However, FA failed to detect the crossing pattern in 10 eyes (21.7%). OCT angiography was significantly more effective for identification of the AV crossing pattern than FA (44 eyes; 95.7%; P = .013). The number of eyes with venous overcrossing detected via OCT angiography (20 eyes, 43.5%) was also higher than that detected via FA (P = .047). OCT angiography revealed that venous narrowing (25.5 ± 21.1 μm) was significantly greater in instances of venous overcrossing than in those of arterial overcrossing (46.4 ± 23.7 μm, P = .005). Macular nonperfusion areas (NPAs) were larger in eyes with venous overcrossing than in those with arterial overcrossing (P = .011 for superficial plexus, P = .049 for deep plexus). The peripheral NPA was significantly larger in eyes with venous overcrossing (65.1 ± 35.3 disc area [DA]) than in those with arterial overcrossing (17.2 ± 24.1 DA; P < .001).

CONCLUSIONS

Our findings suggest that BRVO characterized by venous overcrossing may be more prevalent than previously reported, and that there is a significant association between NPA size and AV crossing pattern.

Quantitative microvascular analysis of retinal venous occlusions by spectral domain optical coherence tomography angiography

Purpose

To quantitatively evaluate the retinal microvasculature in human subjects with retinal venous occlusions (RVO) using optical coherence tomography angiography (OCTA).

Design

Retrospective, cross-sectional, observational case series.

Participants

Sixty subjects (84 eyes) were included (20 BRVO, 14 CRVO, 24 unaffected fellow eyes, and 26 controls).

Methods

OCTA was performed on a prototype, spectral domain-OCTA system in the 3x3mm central macular region. Custom software was used to quantify morphology and density of retinal capillaries using four quantitative parameters. The vasculature of the segmented retinal layers and nonsegmented whole retina were analyzed.

Main outcome measures

Fractal dimension (FD), vessel density (VD), skeletal density (SD), and vessel diameter index (VDI) within the segmented retinal layers and nonsegmented whole retina vasculature.

Results

Nonsegmented analysis of RVO eyes demonstrated significantly lower FD (1.64±0.01 vs 1.715±0.002; p<0.001), VD (0.32±0.01 vs 0.432±0.002; p<0.001), and SD (0.073±0.004 vs 0.099±0.001; p<0.001) compared to controls. Compared to the fellow eye, FD, VD and SD were lower (p<0.001), and VDI was higher (p<0.001). FD, VD, and SD progressively decreased as the extent (or type) of RVO increased (control vs BRVO vs CRVO; p<0.001). In the unaffected fellow eye FD, VD and SD showed significant differences when compared to control eyes or affected RVO eyes (p<0.001).

Conclusions

Quantitative OCTA of the central 3x3mm macular region demonstrates significant differences in capillary density and morphology among subjects with BRVO and CRVO compared to controls or unaffected fellow eyes in all vascular layers. The unaffected fellow eyes also demonstrate significant differences when compared to controls. OCTA allows for noninvasive, layer-specific, quantitative evaluation of RVO-associated microvascular changes.

Optical coherence tomography based angiography [Invited]

Optical coherence tomography (OCT)-based angiography (OCTA) provides in vivo, three-dimensional vascular information by the use of flowing red blood cells as intrinsic contrast agents, enabling the visualization of functional vessel networks within microcirculatory tissue beds non-invasively, without a need of dye injection. Because of these attributes, OCTA has been rapidly translated to clinical ophthalmology within a short period of time in the development. Various OCTA algorithms have been developed to detect the functional micro-vasculatures in vivo by utilizing different components of OCT signals, including phase-signal-based OCTA, intensity-signal-based OCTA and complex-signal-based OCTA. All these algorithms have shown, in one way or another, their clinical values in revealing micro-vasculatures in biological tissues in vivo, identifying abnormal vascular networks or vessel impairment zones in retinal and skin pathologies, detecting vessel patterns and angiogenesis in eyes with age-related macular degeneration and in skin and brain with tumors, and monitoring responses to hypoxia in the brain tissue. The purpose of this paper is to provide a technical oriented overview of the OCTA developments and their potential pre-clinical and clinical applications, and to shed some lights on its future perspectives. Because of its clinical translation to ophthalmology, this review intentionally places a slightly more weight on ophthalmic OCT angiography.

Evaluation of pseudophakic cystoid macular edema using optical coherence tomography angiography

Purpose:

To compare the optical coherence tomography angiography (OCT-A) findings of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) in eyes with pseudophakic cystoid macular edema (PCME) with those of fluorescein angiography (FA) and spectral-domain optical coherence tomography (SD-OCT) and to compare PCME vascular density values of the SCP and DCP with those of healthy eyes.

Methods:

In this retrospective observational study, 13 eyes (12 patients) with PCME underwent comprehensive ophthalmologic examinations including visual acuity, FA, SD-OCT, and OCT-A. The vascular density of the SCP and DCP were measured using AngioAnalytics software in all PCME eyes and compared with 46 healthy eyes of 25 subjects.

Results:

In patients with PCME, at the level of SCP, the mean vascular density in the whole en face image was 44.48 ± 3.61% while it was 50.27 ± 5.30% at the level of the DCP. In contrast, the vascular density in the whole en face image was 50.35 ± 3.22 at the level of SCP while it was 56.15 ± 3.28 at the level of DCP in 46 healthy eyes of 25 subjects. The vascular density of patients with PCME was significantly lower than in healthy subjects at the SCP (p<0.0001) and at the DCP (p<0.0001).

Conclusion:

We report the OCT-A appearance of PCME and vascular density map with values that can be easily interpreted for quantitative evaluation of retina perfusion status using OCT-A. This approach might be the first step in helping us fully understand the pathophysiologic mechanisms underlying PCME.