Evaluation of retinal nonperfusion in branch retinal vein occlusion using wide-field optical coherence tomography angiography

Clinical Utilisation of Wide-Field Optical Coherence Tomography and Angiography: A Narrative Review

Many important abnormalities of the vitreous, retina and choroid are predominantly located in the peripheral retina. In some retinal diseases with both central and peripheral manifestations, pathological structural or vascular changes can be apparent in the periphery before they are detectable in the central retina. Conventional optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A) imaging only cover the most posterior 30° of the retina. Wide-field OCT (WF-OCT), though offering detailed cross-sectional imaging of the peripheral retina, is not yet systematically used in clinical practice. This narrative review provides a presentation of the utilisation of WF-OCT and WF-OCT-A in the diagnosis and monitoring of a variety of ophthalmological diseases and discusses the advantages and limitations of the technology. With the rapidly developing technology, multiple WF-OCT and WF-OCT-A devices are now commercially available and enable the clinician to obtain scans within a field of view up to 200°. As detailed in this review, several studies have shown promising results in the application of WF-OCT and WF-OCT-A in diseases of the retina, choroid and vitreous, such as retinal vein occlusion, diabetic retinopathy, ocular oncology, paediatric ophthalmology, uveitis and lesions of the vitreo-retinal interface. In conclusion, WF-OCT and WF-OCT-A can reliably produce high-quality, non-invasive images of the vitreous, retinal, and choroidal structures and vascularity covering the posterior pole as well as the mid and far periphery. These methods can be a valuable part of a multimodal imaging approach in the management of a variety of ocular conditions. Future studies are warranted to investigate the patient outcome benefits of implementation of WF-OCT and WF-OCT-A imaging in a real-life clinical setting.

Advantages of the Utilization of Wide-Field OCT and Wide-Field OCT Angiography in Clinical Practice

Wide-field (WF) retinal imaging is becoming a standard diagnostic tool for diseases involving the peripheral retina. Technological progress elicited the advent of wide-field optical coherence tomography (WF-OCT) and WF-OCT angiography (WF-OCTA) examinations. This review presents the results of studies that analyzed the implementation of these procedures in clinical practice and refers to them as traditional and ultra-wide-field fluorescein angiography (UWF-FA). A PUBMED search was performed using the terms WF-OCT OR WF-OCTA OR UWF-FA AND the specific clinical entity, and another search for diabetic retinopathy (DR), retinal vein occlusion (RVO), Coats disease, peripheral retinal telangiectasia, peripheral retinal degeneration, lattice degeneration, and posterior vitreous detachment. The analysis only included the studies in which the analyzed field of view for the OCT or OCTA exam was larger than 55 degrees. The evaluation of the extracted studies indicates that WF imaging with OCT and OCTA provides substantial information on retinal disorders involving the peripheral retina. Vascular diseases, such as DR or RVO, can be reliably evaluated using WF-OCTA with results superior to standard-field fluorescein angiography. Nevertheless, UWF-FA provides a larger field of view and still has advantages over WF-OCTA concerning the evaluation of areas of non-perfusion and peripheral neovascularization. Detailed information on the vascular morphology of peripheral changes should be obtained via WF-OCTA and not angiographic examinations. WF-OCT can serve as a valuable tool for the detection and evaluation of vitreoretinal traction, posterior vitreous detachment, and peripheral retinal degeneration, and guide therapeutic decisions on a patient's eligibility for surgical procedures.

Hybrid Fusion of High-Resolution and Ultra-Widefield OCTA Acquisitions for the Automatic Diagnosis of Diabetic Retinopathy

Optical coherence tomography angiography (OCTA) can deliver enhanced diagnosis for diabetic retinopathy (DR). This study evaluated a deep learning (DL) algorithm for automatic DR severity assessment using high-resolution and ultra-widefield (UWF) OCTA. Diabetic patients were examined with 6×6 mm2 high-resolution OCTA and 15×15 mm2 UWF-OCTA using PLEX®Elite 9000. A novel DL algorithm was trained for automatic DR severity inference using both OCTA acquisitions. The algorithm employed a unique hybrid fusion framework, integrating structural and flow information from both acquisitions. It was trained on data from 875 eyes of 444 patients. Tested on 53 patients (97 eyes), the algorithm achieved a good area under the receiver operating characteristic curve (AUC) for detecting DR (0.8868), moderate non-proliferative DR (0.8276), severe non-proliferative DR (0.8376), and proliferative/treated DR (0.9070). These results significantly outperformed detection with the 6×6 mm2 (AUC = 0.8462, 0.7793, 0.7889, and 0.8104, respectively) or 15×15 mm2 (AUC = 0.8251, 0.7745, 0.7967, and 0.8786, respectively) acquisitions alone. Thus, combining high-resolution and UWF-OCTA acquisitions holds the potential for improved early and late-stage DR detection, offering a foundation for enhancing DR management and a clear path for future works involving expanded datasets and integrating additional imaging modalities.

Clinical utility of ultra-widefield fluorescein angiography and optical coherence tomography angiography for retinal vein occlusions

Retinal vein occlusions (RVOs) are the second most common retinal vascular disease after diabetic retinopathy, and are a significant cause of visual impairment, especially in the elderly population. RVOs result in visual loss due to macular ischemia, cystoid macular edema (CME), and complications related to neovascularization. Vascular assessment in RVOs traditionally relies on standard fluorescein angiography (FA) for assessment of macular and retinal ischemia, which aids in prognostication and guides intervention. Standard FA has significant limitations-it is time-consuming, requires invasive dye administration, allows for limited assessment of the peripheral retina, and is usually evaluated semi-qualitatively, by ophthalmologists with tertiary expertise. More recently, the introduction of ultra-widefield FA (UWF FA) and optical coherence tomography angiography (OCTA) into clinical practice has changed the tools available for vascular evaluation in RVOs. UWF FA allows for evaluation of peripheral retinal perfusion, and OCTA is non-invasive, rapidly-acquired, and provides more information on capillary perfusion. Both modalities can be used to provide more quantitative parameters related to retinal perfusion. In this article, we review the clinical utility and impact of UWF FA and OCTA in the evaluation and management of patients with RVOs.

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.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Background

The fast development of swept-source optical coherence tomography (SS-OCT) and swept-source optical coherence tomography angiography (SS-OCTA) enables both anterior and posterior imaging of the eye. These techniques have evolved from a research tool to an essential clinical imaging modality.

Main text

The longer wavelength and faster speed of SS-OCT and SS-OCTA facilitate better visualization of structure and vasculature below pigmented tissue with a larger field of view of the posterior segment and 360-degree visualization of the anterior segment. In the past 10 years, algorithms dealing with OCT and OCTA data also vastly improved the image quality and enabled the automated quantification of OCT- and OCTA-derived metrics. This technology has enriched our current understanding of healthy and diseased eyes. Even though the high cost of the systems currently limited the widespread use of SS-OCT and SS-OCTA at the first beginning, the gap between research and clinic practice got obviously shortened in the past few years.

Conclusions

SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift toward more widespread adoption of new imaging technology in clinical practice.

Microvascular Changes in the Cystic Lesion of Branch Retinal Vein Occlusion Imaged by Swept-Source Optical Coherence Tomography Angiography

<b><i>Introduction:</i></b> This study aimed to describe the quantitative features of the microvasculature in the cystic lesions of branch retinal vein occlusion (BRVO). <b><i>Methods:</i></b> A total of 43 eyes with BRVO, treated with anti-vascular endothelial growth factor therapy, were analyzed. Using wide-field swept-source optical coherence tomography angiography (OCTA), en face OCT images were obtained by depth-integrated reflectivity of the retina, and vascular density (VD), vascular length (VL), vascular lacunarity, and fractal dimension (FD) were evaluated in a 12 × 12-mm area of retinal nonperfusion. <b><i>Results:</i></b> The mean area of affected lesions was 38.7 ± 19.8 mm², and cystic lesions were 8.5 ± 10.1 mm². VD, VL, and FD were significantly decreased in the cystic lesions compared to other affected lesions in the same eyes (<i>p</i> = 0.0010, <i>p</i> = 0.0001, and <i>p</i> = 0.0003, respectively) and in all eyes (<i>p</i> = 0.0281, <i>p</i> = 0.0050, and <i>p</i> &#x3c; 0.0001, respectively). VD in cystic lesions within the vascular arcade (25 eyes) correlated with best-corrected visual acuity on OCTA (<i>r</i> = −0.433, and <i>p</i> = 0.0492). <b><i>Conclusions:</i></b> Vascular structure in the cystic lesions was unpreserved compared to the other lesions in BRVO. These findings may help in understanding the pathophysiology of retinal edema in BRVO.

Retinal Vessel Density and Treatment Intensity among Adults with Retinal Vein Occlusion: A Swept-Source Optical Coherence Tomography Angiography Study

Previous studies have shown retinal vein occlusion (RVO) is associated with changes in vessel density visible on swept-source optical coherence tomography angiography (ss-OCTA). This study aimed to characterize retinal changes on ss-OCTA among RVO patients stratified by the need for continuous anti-VEGF therapy. This cross-sectional study of 24 RVO patients ≥ 18 years were imaged with SS-OCT-A. Patients were categorized into continuous vs. limited therapy (≥1 vs. no injections in previous 12 months) based on recurrence of intraretinal fluid (IRF) on OCT. Images were analyzed using ImageJ. T-tests were used to compare vessel density of the macula and peripheral retina. Overall, RVO patients undergoing continuous therapy (n = 14) had higher diabetes prevalence, worse baseline visual acuity, and higher baseline macular thickness compared to the limited (n = 10) therapy group. Continuous therapy was associated with lower macular VD in the combined retina layer and the superficial capillary plexus (SCP), but not in the deep capillary plexus (DCP). Further, the continuous therapy group exhibited lower peripheral VD in the combined retina layer, and no difference in the SCP and DCP layers when analyzed separately. In conclusion, RVO patients requiring continuous anti-VEGF injections demonstrate reduced VD of the macula and in the periphery on SS-OCTA imaging. SS-OCTA may be valuable for monitoring and prognosticating treatment for RVO patients.

Optical Coherence Tomography Angiography: Clinical Utility and Future Directions

Purpose

This work aims to review the principles of optical coherence tomography angiography (OCTA), to survey its clinical utility, and to highlight the strengths of this technology as well as barriers to adoption.

Methods

A literature review with editorial discussion of the current applications for OCTA is presented.

Results

There have been recent advances in multiple domains in OCTA imaging, including devices, algorithms, and new observations pertaining to a range of pathologies. New devices have improved the scanning speed, signal-to-noise ratio, and spatial resolution and offer an increased field of view. New algorithms have been proposed to optimize image processing and reduce artifacts. Numerous studies employing OCTA have been published describing changes to the microvasculature in diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, retinal vein occlusion, and uveitis.

Conclusions

OCTA provides noninvasive, high-resolution volumetric scans of the retinal and choroidal vasculature. OCTA can provide valuable data to augment traditional dye-based angiography in a range of chorioretinal diseases.

Deep learning-based classification of retinal vascular diseases using ultra-widefield colour fundus photographs

Objective

To assess the ability of a deep learning model to distinguish between diabetic retinopathy (DR), sickle cell retinopathy (SCR), retinal vein occlusions (RVOs) and healthy eyes using ultra-widefield colour fundus photography (UWF-CFP).

Methods and Analysis

In this retrospective study, UWF-CFP images of patients with retinal vascular disease (DR, RVO, and SCR) and healthy controls were included. The images were used to train a multilayer deep convolutional neural network to differentiate on UWF-CFP between different vascular diseases and healthy controls. A total of 224 UWF-CFP images were included, of which 169 images were of retinal vascular diseases and 55 were healthy controls. A cross-validation technique was used to ensure that every image from the dataset was tested once. Established augmentation techniques were applied to enhance performances, along with an Adam optimiser for training. The visualisation method was integrated gradient visualisation.

Results

The best performance of the model was obtained using 10 epochs, with an overall accuracy of 88.4%. For DR, the area under the receiver operating characteristics (ROC) curve (AUC) was 90.5% and the accuracy was 85.2%. For RVO, the AUC was 91.2% and the accuracy 88.4%. For SCR, the AUC was 96.7% and the accuracy 93.8%. For healthy controls, the ROC was 88.5% with an accuracy that reached 86.2%.

Conclusion

Deep learning algorithms can classify several retinal vascular diseases on UWF-CPF with good accuracy. This technology may be a useful tool for telemedicine and areas with a shortage of ophthalmic care.

WF SS-OCTA for detecting diabetic retinopathy and evaluating the effect of photocoagulation on posterior vitreous detachment

PURPOSE

This study aimed to assess the clinical usefulness of widefield swept source optical coherence tomography angiography (WF SS-OCTA) for detecting microvasculature lesions in diabetic retinopathy (DR) by comparing it with ultra-widefield fluorescein angiography (UWFFA) and to investigate the effect of panretinal photocoagulation (PRP) on posterior vitreous detachment (PVD) status.

METHODS

Patients with severe non-proliferative DR (NPDR) or proliferative DR (PDR) who were initially treated with PRP were enrolled. They underwent WF SS-OCTA with a 12×12-mm scan pattern of five visual fixations at baseline and at least a 3-month follow-up after PRP treatment. Patients with no contraindications underwent imaging with UWFFA within a week. Images were evaluated using two methods for the areas of the visible field of view (FOV), non-perfusion area (NPA), presence of neovascularization of the disc (NVD), neovascularization elsewhere (NVE), and PVD status.

RESULTS

In total, 44 eyes of 28 patients with DR that were initially treated with PRP were analyzed. The FOV of the UWFFA was significantly wider than that of the WF SS-OCTA. The quantitative measurement of the NPAs was consistent between the two methods. NPAs more than 5DA outside the panoramic OCTA imaging area were detected in 1 eye with NPDR (8.3%) and in 10 eyes with PDR (47.8%). WF SS-OCTA had high detection rates for NVDs and NVEs, with a low rate of false positives. After PRP treatment, no eyes indicated progression in the PVD stages around the macula, optical disc, or NVEs at the short follow-up.

CONCLUSION

WF SS-OCTA is clinically useful for evaluating NPAs and neovascularization in DR. PRP treatment does not induce PVD development in the short term.

Research progress of UWFFA and OCTA in retinal vein occlusion: A review

Retinal vein occlusion (RVO) is a retinal vascular disease that severely impairs the visual function of patients. Observing the changes of retinal blood vessels before and after treatment is of great significance for the prognostic evaluation of RVO. The rapid development and widespread use of fundus imaging technique, especially ultra-wide-angle fundus fluorescein angiography (UWFFA) and optical coherence tomography angiography (OCTA) have made our observation of the retinal blood vessels of RVO more comprehensive and meticulous. In this paper, we reviewed the latest research progress of UWFFA and OCTA in RVO.

Phenotyping of retinal neovascularization in ischemic retinal vein occlusion using wide field OCT angiography

BACKGROUND/OBJECTIVES

Abnormal retinal neovascularization caused by ischemic retinal vein occlusion (RVO) is a frequent cause of visually significant vitreous hemorrhage. The early detection of new vessels may be challenging and often requires the use of invasive tests such as fundus fluorescein angiography (FA). We demonstrate the use of wide-field optical coherence tomography angiography (WF-OCTA) in the detection and characterization of neovascularization secondary to ischemic RVO.

SUBJECTS/METHODS

We conducted a retrospective observational case series of patients diagnosed with ischemic RVO between August 2018 and March 2019, who underwent WF-SS-OCTA imaging (PLEX Elite 9000, Carl Zeiss Meditec). We performed real-life montage imaging, covering the involved area and compared the findings of WF-SS-OCTA to standard clinical examination and when available, ultrawide-field fluorescein angiography (UWF-FA, Optos 200TX).

RESULTS

In the included 39 eyes with ischemic RVO, neovascularization elsewhere (NVE) was encountered in 16 of 39 eyes (41%) on WF-OCTA and were characterized as sea-fan type vessels and nodular type vessels, based on their appearance and localization. NVE was identified in 4/39 eyes on standard clinical examination, equating to a detection rate of 10.3%. All were of a sea-fan morphology. In one case, NVE found on WF-OCTA was not observed on UWF-FA, which was a nodular type. Neovascularization of the disc (NVD) was detected in one eye.

CONCLUSIONS

WF-OCTA may become a useful noninvasive tool in the detection of neovascularization in patients with ischemic RVO. Furthermore, the characterization of different morphologies of neovascularization detected by WF-OCTA could be of clinical relevance.

Quantification of Nonperfusion Area in Montaged Widefield OCT Angiography Using Deep Learning in Diabetic Retinopathy

Purpose

To examine the efficacy of a deep learning-based algorithm to quantify the nonperfusion area (NPA) on montaged widefield OCT angiography (OCTA) for assessment of diabetic retinopathy (DR) severity.

Design

Cross-sectional study.

Participants

One hundred thirty-seven participants with a full range of DR severity and 26 healthy participants.

Methods

A deep learning-based algorithm was developed for detecting and quantifying NPA in the superficial vascular complex on widefield OCTA comprising 3 horizontally montaged 6 × 6-mm OCTA scans from the nasal, macular, and temporal regions. We trained the algorithm on 978 volumetric OCTA scans from all participants using 5-fold cross-validation. The algorithm can distinguish NPA from shadow artifacts. The F1 score evaluated segmentation accuracy. The area under the receiver operating characteristic curve and sensitivity with specificity fixed at 95% quantified network performance to distinguish patients with diabetes from healthy control participants, referable DR from nonreferable DR (nonproliferative DR [NPDR] less than moderate severity), and severe DR (severe NPDR, proliferative DR, or DR with edema) from nonsevere DR (mild to moderate NPDR).

Main Outcome Measures

Widefield OCTA NPA, visual acuity (VA), and DR severities.

Results

Automatically segmented NPA showed high agreement with the manually delineated ground truth, with a mean ± standard deviation F1 score of 0.78 ± 0.05 in nasal, 0.82 ± 0.07 in macular, and 0.78 ± 0.05 in temporal scans. The extrafoveal avascular area (EAA) in the macular scan showed the best sensitivity at 54% for differentiating those with diabetes from healthy control participants, whereas montaged widefield OCTA scan showed significantly higher sensitivity than macular scans (P < 0.0001, McNemar’s test) for detecting eyes with DR at 66%, referable DR at 63%, and severe DR at 62%. Montaged widefield OCTA showed the highest correlation (Spearman ρ = 0.74; P < 0.0001) between EAA and DR severity. The macular scan showed the strongest negative correlation (Pearson ρ = –0.42; P < 0.0001) between EAA and best-corrected VA.

Conclusions

A deep learning-based algorithm for montaged widefield OCTA can detect NPA accurately and can improve the detection of clinically important DR.

Analysis of Progressive Neovascularization in Diabetic Retinopathy Using Widefield OCT Angiography

PURPOSE

To document enlarged neovascularization elsewhere (NVE) quantitatively and morphologically using widefield swept-source (SS) OCT angiography (OCTA) with vitreoretinal interface (VRI) slab images.

DESIGN

Retrospective, observational imaging study.

PARTICIPANTS

The study included 46 NVE examples in 25 eyes of 21 consecutive patients who demonstrated severe proliferative diabetic retinopathy with NVE between March 2018 and June 2020 at Osaka University Hospital.

METHODS

All patients underwent ophthalmologic examination, including ultra-widefield fluorescein angiography and widefield SS OCTA scans.

MAIN OUTCOME MEASURES

We evaluated the area and the vascular density (VD) of NVE lesions detected on five 12 × 12-mm² or two 15 × 9-mm² SS OCTA panoramic VRI slab images obtained at the first and final visits.

RESULTS

At baseline, the mean NVE area on OCTA was 1.85 ± 2.81 mm², and the VD of the NVE lesions was 73.9 ± 14.6%. At the final visit, the mean NVE area on OCTA was 2.14 ± 3.14 mm², and the mean VD of the NVE lesions was 65.3 ± 17.1%. The average NVE size change (square millimeters per month) was associated significantly with the ischemic index (P = 0.009). Growth of NVE area was classified into 2 patterns: round (61.8%) and ramified (38.2%). The round group tended to have a larger ischemic index at baseline than the ramified group (P = 0.0375).

CONCLUSIONS

We quantified the size and density of NVE lesions over time. The NVE size increase was associated significantly with the severity of ischemic changes. Furthermore, the round growth pattern was correlated significantly with the ischemic index. These findings suggest that the morphologic features of NVE are associated with more severe ischemia.

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.

Association of disorganization of retinal inner layers with optical coherence tomography angiography features in branch retinal vein occlusion

PURPOSE

To examine the associations between the disorganization of the retinal inner layers (DRIL) and optical coherence tomography angiography characteristics and visual acuity (VA) outcomes in eyes with macular edema secondary to branch retinal vein occlusion (BRVO).

METHODS

In this single-center cross-sectional cohort study, the data of 43 patients with macular edema secondary to BRVO that received pro re nata anti-vascular endothelial growth factor therapy were analyzed. B-scan and en face angiographic images were obtained by swept-source-based wide-field optical coherence tomography angiography performed at a single visit 1 month after the anti-vascular endothelial growth factor therapy session and evaluated. Correlations between the vascular indices in macula-centered 3 × 3 and 12 × 12 mm² areas and B-scan parameters, such as DRIL length and VA, were examined.

RESULTS

The mean DRIL length (Rs = 0.588, p < 0.001) and the proportion of scans with DRIL out of five scans (Rs = 0.507, p = 0.001) were significantly correlated with the final best-corrected VA in patients with BRVO. DRIL length was associated with vascular density (VD) and vascular length in the macula (Rs =  - 0.425, p = 0.006 and Rs =  - 0.382, p = 0.013, respectively), but not with VD and vascular length in the larger areas (12 × 12 mm²). Multilinear regression analysis revealed that the extent of macular edema (p = 0.0016) and VD in the 3 × 3 mm² area (p = 0.004) was significantly associated with the DRIL development.

CONCLUSION

DRIL severity was correlated with VA and associated with the peri-macular perfusion status in eyes with BRVO. Macular edema and macular perfusion affected DRIL severity. These findings would help understand the pathogenesis of DRIL in eyes with BRVO.

Recent advances in wide field and ultrawide field optical coherence tomography angiography in retinochoroidal pathologies

Introduction: With the advent of wide field (WF) and ultra-wide field (UWF) imaging in color fundus photography and fluorescein angiography (FA), the importance of an expanded field-of-view (FOV) has been illustrated for early detection of several chorioretinal disorders. The need to bring similar utility to optical coherence tomography angiography (OCTA) is imperative.Areas covered: For this review, we explored all research items with WF or UWF on Pubmed Central and Google Scholar. Software-based methods included algorithms for motion correction, artifact reduction, image pre-processing, post-processing and montage protocols while hardware methods included swept-source OCTA, faster scanning sources, hardware-based motion tracking and image registration, scanning sources with faster speeds and lower resolution. For various disorders such as diabetic retinopathy, uveitis, vascular disorders, among others, the increased FOV showed demonstrably increased detection rates and diagnostic yield.Expert opinion: Increased FOV in OCTA imaging is a meaningful and impactful step in ophthalmic imaging. Overcoming the hardware-based limitations can potentially yield higher FOV without loss of important details. In addition to improvements in the hardware and available equipment, better software tools and image processing algorithms may greatly enhance the utility of UWF OCTA in care of patients with various retinochoroidal diseases.

Relative Retinal Blood Flow: A Novel and Informative Measure of Unilateral Retinal Vein Occlusion Severity

Purpose

This study quantifies retinal vascular blood flow affected by unilateral central or branch retinal vein occlusion (CRVO or BRVO). We created a new, unitless metric for the severity of these diseases—relative blood flow (RBF)—and contextualized it with subject demographics, ocular presentation, and systemic conditions. Finally, we explored its efficacy as a predictor of future outcomes.

Methods

Data were collected from 20 control subjects and 32 clinically diagnosed CRVO (n = 15) or BRVO (n = 17) patients. We used laser speckle flowgraphy to quantify blood flow as mean blur rate and present RBF as the ratio between the blood flow in a subject's diseased and undiseased eyes. Because of our demonstration that blood flow has high intrapatient (between eyes and over time) but low interpatient correlation in eyes of healthy subjects, any differences between eyes can be attributed to the disease. These data were correlated with subject demographics and disease characteristics.

Results

In CRVO and BRVO eyes, average blood flow decreased by 26% and 7%, respectively. In CRVO, occlusion duration, central macular thickness, intraocular pressure, diabetes, previous laser and injection treatments, and injection within three months after measurement were significantly associated with RBF. In BRVO, no significant associations with RBF were found.

Conclusions

Blood flow in CRVO and BRVO was reduced compared to the unaffected fellow eye in most patients. RBF was useful in determining the severity of RVOs and predicting future treatment needs.

Translational Relevance

RBF is a promising new and informative metric for quantifying the severity of unilateral RVOs.

Wide-Field Swept-Source Optical Coherence Tomography Angiography Analysis of the Periarterial Capillary-Free Zone in Branch Retinal Vein Occlusion

Purpose

To investigate the characteristics of the retinal periarterial capillary-free zone (paCFZ) with wide-field swept-source optical coherence tomography angiography (SS-OCTA) in eyes with branch retinal vein occlusion (BRVO).

Methods

Seventy treatment-naïve eyes with BRVO and 35 healthy eyes were included. The paCFZ areas, artery calibers, and areas of the major arteries in the unaffected quadrants of BRVO eyes were measured in 12 × 12-mm SS-OCTA images and compared with those of the contralateral eyes and healthy eyes. Other multimodal imaging data were collected.

Results

There were no significant differences in the unaffected artery caliber or area among the three groups (all P > 0.05). The unaffected paCFZ areas and the ratios of the unaffected paCFZ area to the counterpart artery area (paCFZ/artery area) of the major arteries were significantly larger than those in the contralateral or healthy eyes (all P < 0.05). Subgroup analysis revealed that the paCFZ/artery area value differed significantly between ischemic and nonischemic BRVO eyes (P < 0.01). The paCFZ/artery area value was positively correlated with logMAR best-corrected visual acuity, symptom duration, central macular thickness, and retinal nonperfusion area in BRVO.

Conclusions

Quantitative SS-OCTA measurements confirmed enlarged paCFZs along the unaffected major retinal arteries in BRVO eyes. The paCFZ parameters were correlated with symptom duration, retinal ischemia, and visual function.

Translational Relevance

Retinal periarterial capillary-free zones in BRVO can be non-invasively measured by SS-OCTA, assisting in clinically identifying retinal ischemia and evaluating visual function.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Wide-Field Fluorescein Angiography in the Diagnosis and Management of Retinal Vein Occlusion: A Retrospective Single-Center Study

Background

The aim of this retrospective study was to evaluate the role of wide-field fluorescein angiography (WF-FA) in the diagnosis and management of retinal vein occlusion (RVO) at a single center in Poland.

Material/Methods

This study included 106 patients (112 eyes) diagnosed with RVO (102 eyes) or impending RVO (10 eyes) (54% women and 46% men, aged 26 to 86 years). The medical records of the participants were reviewed in search of documentation on ocular and systemic diseases. Results of FA of central and peripheral retina and optical coherence tomography (OCT) scans, which had been used to establish treatment indications, were analyzed. WF-FA was performed with Spectralis HRA+OCT or Optos Tx200.

Results

Actual RVO was found in 102 eyes. Of those cases, 46.1% were CRVO (central retinal vein occlusion), 40.2% branch retinal vein occlusion, 11.8% small tributary vein occlusion, and 1.9% hemispheric retinal vein occlusion. Neovascularization on an optic disc, neovascularization elsewhere, and veno-venous collateral vessels were observed in 32.3%, 17.4%, and 41.2% of the eyes, respectively. Peripheral ischemic zones were present in 59.8% of the eyes, in 20.6% of which, ischemia was not observed in the posterior pole. Dye leaks limited to peripheral vessels, peripheral vascular amputations, and central macular edema in OCT were observed in 17.6%, 43.1%, and 63.7% of the eyes, respectively. Retinal laser photocoagulation was conducted on 73.5% of the eyes.

Conclusions

Decision-making about management of patients with RVO should be done after physical examination and analysis of central and peripheral retina FA. In 20.6% of patients, assessment of the peripheral retina resulted in a change in treatment. The first changes suggestive of progression of thrombotic disease to the ischemic form appeared on the periphery in images from WF-FA.

Effect of vessel enhancement filters on the repeatability of measurements obtained from widefield swept-source optical coherence tomography angiography

We assessed the inter-visit repeatability of 15 × 9-mm² swept-source OCTA (SS-OCTA; PLEX Elite 9000, Carl Zeiss Meditec) metrics in 14 healthy participants. We analysed the perfusion density (PD) of large vessels, superficial capillary plexus (SCP), and deep capillary plexus (DCP) as well as choriocapillaris flow voids in 2 different regions: the macular region and peripheral region. Also, retinal plexus metrics were processed further using different filters (Hessian, Gabor and Bayesian) while choriocapillaris flow voids were calculated with 1 and 1.25 standard deviation (SD) thresholding algorithms. We found excellent repeatability in the perfusion densities of large vessels (ICC > 0.96). Perfusion densities varied with different filters in the macular region (SCP: 24.12–38.57% and DCP: 25.16–38.50%) and peripheral (SCP: 30.52–39.84% and DCP: 34.19–41.60%) regions. The ICCs were lower in the macular region compared to the peripheral region and lower for DCP than for SCP. For choriocapillaris flow voids, the 1.25 SD threshold resulted in fewer flow voids, while a good ICC (ICC > 0.81) was achieved using either threshold settings for flow void features in both regions. Our results suggest good repeatability of widefield SS-OCTA for the measurements of retinal perfusion density and choriocapillaris flow voids, but measurements from different filters should not be interchanged.

Optical coherence tomography angiography for visualization of retinal capillary plexuses in pachychoroid neovasculopathy

OBJECTIVE

To evaluate retinal capillary plexus alterations in patients with pachychoroid neovasculopathy (PNV) by optical coherence tomographic angiography (OCTA).

DESIGN

Retrospective observational study.

PARTICIPANTS

The study included 43 patients with PNV (43 eyes, PNV group) and 43 normal eyes (control group).

METHODS

All PNV participants underwent comprehensive ophthalmic examinations, including OCTA. The results were compared with those of the controls. Differences in superficial and deep vascular density between the groups were analyzed. The correlations between vascular density and subfoveal choroidal thickness (SFCT), age, best-corrected visual acuity, refraction, and axial length were analyzed.

RESULTS

The superficial vascular density of the macular region (except for the area of the fovea and the inferior parafoveal region) was significantly lower in the PNV group than the control group (p < 0.05). The deep vascular density of the macular region was significantly lower in the PNV group (p < 0.05). In the PNV group, there was no significant correlation between vascular density and SFCT, age, BVCA, refraction, or axial length (p > 0.05).

CONCLUSIONS

Superficial and deep vascular densities of the macular region were lower in the patients with PNV compared with the patients in the control group. In the patients with PNV, the macular region showed signs of inner retinal capillary dropout, which may be caused by choroidal ischemia and/or a chronic impairment of nutrient supply to the retinal pigment epithelium.