Retinal Ischaemia in Diabetic Retinopathy: Understanding and Overcoming a Therapeutic Challenge

BACKGROUND

Retinal ischaemia is present to a greater or lesser extent in all eyes with diabetic retinopathy (DR). Nonetheless, our understanding of its pathogenic mechanisms, risk factors, as well as other characteristics of retinal ischaemia in DR is very limited. To date, there is no treatment to revascularise ischaemic retina.

METHODS

Review of the literature highlighting the current knowledge on the topic of retinal ischaemia in DR, important observations made, and underlying gaps for which research is needed.

RESULTS

A very scarce number of clinical studies, mostly cross-sectional, have evaluated specifically retinal ischaemia in DR. Interindividual variability on its natural course and consequences, including the development of its major complications, namely diabetic macular ischaemia and proliferative diabetic retinopathy, have not been investigated. The in situ, surrounding, and distance effect of retinal ischaemia on retinal function and structure and its change over time remains also to be elucidated. Treatments to prevent the development of retinal ischaemia and, importantly, to achieve retinal reperfusion once capillary drop out has ensued, are very much needed and remain to be developed.

CONCLUSION

Research into retinal ischaemia in diabetes should be a priority to save sight.

Use of Ultra-Widefield Fluorescein Angiography to Guide the Treatment to Idiopathic Retinal Vasculitis, Aneurysms, and Neuroretinitis-Case Report and Literature Review

PURPOSE

To review the clinical features, diagnosis, and treatment of idiopathic retinal vasculitis, aneurysms, and neuroretinitis (IRVAN) and to report a case with the use of ultra-widefield fluorescein angiography (UWFA) for confirming the precise staging of IRVAN and aid in early treatment. The patient improved after being treated with intravitreal aflibercept injection.

RESULTS

A 26-year-old female complained of progressive blurred vision OD for one week. Her BCVA was 0.6 OD and 1.0 OS. Fundus examination showed vitritis, retinal hemorrhage, and vasculitis over bilateral eyes. Fluorescein angiography (FA) with a 55 degree of view revealed aneurysmal dilations of the peripapillary arteriole, peripapillary focal leakage, venous leakage, and capillary nonperfusion area. Stage 2 IRVAN was impressed OU. Oral prednisolone was administered. After four months, she experienced decreased visual acuity OS. Optical coherence tomography (OCT) revealed subretinal and intraretinal fluid with hyperreflective material. One posterior subtenon triamcinolone and one intravitreal aflibercept injection were performed OS, and macular edema subsided. A 105-degree ultra-widefield fluorescein angiography (UWFA) showed multiple peripheral background hypofluorescence areas corresponding to capillary nonperfusion. Retinal neovascularization (NV) was found OS, which had not been revealed by the previous 55-degree FA. Stage 3 IRVAN was made OS and panretinal laser photocoagulation (PRP) was performed. Oral prednisone and cyclosporine were prescribed. Her vision improved to 1.0 OU.

CONCLUSION

UWFA provides visualization of peripheral retinal pathology and for precise staging. It also had direct implications in the follow-up and treatment strategy.

Evaluating the utility of deep learning for predicting therapeutic response in diabetic eye disease

Purpose

Deep learning (DL) is a technique explored within ophthalmology that requires large datasets to distinguish feature representations with high diagnostic performance. There is a need for developing DL approaches to predict therapeutic response, but completed clinical trial datasets are limited in size. Predicting treatment response is more complex than disease diagnosis, where hallmarks of treatment response are subtle. This study seeks to understand the utility of DL for clinical problems in ophthalmology such as predicting treatment response and where large sample sizes for model training are not available.

Materials and Methods

Four DL architectures were trained using cross-validated transfer learning to classify ultra-widefield angiograms (UWFA) and fluid-compartmentalized optical coherence tomography (OCT) images from a completed clinical trial (PERMEATE) dataset (n=29) as tolerating or requiring extended interval Anti-VEGF dosing. UWFA images (n=217) from the Anti-VEGF study were divided into five increasingly larger subsets to evaluate the influence of dataset size on performance. Class activation maps (CAMs) were generated to identify regions of model attention.

Results

The best performing DL model had a mean AUC of 0.507 ± 0.042 on UWFA images, and highest observed AUC of 0.503 for fluid-compartmentalized OCT images. DL had a best performing AUC of 0.634 when dataset size was incrementally increased. Resulting CAMs show inconsistent regions of interest.

Conclusions

This study demonstrated the limitations of DL for predicting therapeutic response when large datasets were not available for model training. Our findings suggest the need for hand-crafted approaches for complex and data scarce prediction problems in ophthalmology.

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.

Quantitative analysis of retinal vasculature in normal eyes using ultra-widefield fluorescein angiography

AIM

To quantify the area and density of retinal vascularity by ultra-widefield fluorescein angiography (UWFA).

METHODS

In a retrospective study, UWFA images were obtained using an ultra-widefield imaging device in 42 normal eyes of 42 patients. Central and peripheral steered images were used to define the edge of retinal vasculature by a certified grader. The length from the center of the optic disc to the edge of retinal vascularity (RVL) in each quadrant and the total retinal vascular perfusion area (RVPA) were determined by the grader using OptosAdvance software. The density of retinal vascularity (RVD) was quantified in different zones of central-steered images using Image J software.

RESULTS

Among 42 healthy eyes, the values for mean RVL in each quadrant were 19.007±0.781 mm (superior), 18.467±0.869 mm (inferior), 17.738±0.622 mm (nasal) and 24.241±1.336 mm (temporal). The mean RVPA was 1140.117±73.825 mm². The mean RVD of the total retina was 4.850%±0.638%. RVD varied significantly between different retina zones (P<0.001), and significant differences existed in the RVD values for total retinal area in patients over 50 years old compared to those under 50 years old (P=0.033). No gender difference was found.

CONCLUSION

The UWFA device can be a promising tool for analyzing the overall retinal vasculature and may provide a better understanding of retinal vascular morphology in normal eyes. Aging may be related to lower RVD.

Vascular abnormalities may progress in branch vein occlusion despite resolution of macular edema

Progression of vascular abnormalities was assessed between resolved and persistent macular edema (ME) in branch retinal vein occlusion. Progression was more common in eyes with resolved ME, suggesting that resolved ME may not signify stability.

The 2-Year Leakage Index and Quantitative Microaneurysm Results of the RECOVERY Study: Quantitative Ultra-Widefield Findings in Proliferative Diabetic Retinopathy Treated with Intravitreal Aflibercept

Eyes with proliferative diabetic retinopathy (PDR) have been shown to improve in the leakage index and microaneurysm (MA) count after intravitreal aflibercept (IAI) treatment. The authors investigated these changes via automatic segmentation on ultra-widefield fluorescein angiography (UWFA). Forty subjects with PDR were randomized to receive either 2 mg IAI every 4 weeks (Arm 1) or every 12 weeks (Arm 2) through Year 1. After Year 1, Arm 1 switched to quarterly IAI and Arm 2 to monthly IAI through Year 2. By Year 2, the Arm 1 leakage index decreased by 43% from Baseline (p = 0.03) but increased by 59% from Year 1 (p = 0.04). Arm 2 decreased by 61% from Baseline (p = 0.008) and by 31% from Year 1 (p = 0.12). Both cohorts exhibited a significant decline in MAs from Baseline to Year 2 (871 to 410; p < 0.001; 776 to 207; p < 0.001, respectively). Subjects with an improved leakage and MA count showed a more significant improvement in the Diabetic Retinopathy Severity Scale (DRSS) score. Moreover, central subfield thickness (CST) was positively associated with changes in the leakage index. In conclusion, the leakage index and MA counts significantly improved from Baseline following IAI treatment, and monthly injections provided a more rapid and sustained reduction in these parameters compared with quarterly injections.

Peripheral arterial filling time and peripheral retina fluorescence features in ultra-widefield angiography

AIM

To evaluate the peripheral arterial filling time (PAFT) and venous filling time (VFT) in eyes without known diseases that may influence filling process using ultra-widefield (UWF) fluorescein angiography (FA), and to review the peripheral retina fluorescence features.

METHODS

A total of 30 eyes of 30 patients were retrospectively reviewed in this observational study. UWF-FA was performed using Optos 200Tx. PAFT and VFT was recorded. The interval between the arterial or venous filling completion and the previous photo was documented. The appearance of the far peripheral retina was described as either granular background fluorescence or mottled fluorescent band or vascular leakage. Terminal vascular patterns was described as loop pattern or branching pattern. Microvascular abnormalities such as arteriovenous shunting, vessels crossing the horizontal raphe, right angle vessels, terminal networks, capillary nonperfusion, drusen or microaneurysms were evaluated.

RESULTS

The normal limits of PAFT was 3.397-8.984s and 4.399-11.753s for VFT. The appearance of the far peripheral retina, defined as granular background (63%), mottled fluorescence (20%), or vascular leakage (17%), was symmetrical between both eyes. Capillary nonperfusion (23%) and microaneurysms (40%) were more frequently found in eyes with loop pattern than in eyes with branching pattern. Other peripheral signs such as right-angle vessels (73%), and terminal networks (80%) were commonly seen on UWF-FA in the normal peripheral retina.

CONCLUSION

The main courses of retinal artery and vein filling time are overlapping with each other on UWF-FA. Notably, the arterial filling process is completed in the arteriovenous phase rather than the traditionally named arterial phase. There are various manifestations in the peripheral retina of normal eyes.

Dynamic versus static ultra-widefield fluorescein angiography in eyes with diabetic retinopathy: a pilot prospective cross-sectional study

AIM

To analyze differences in ultra-widefield fluorescein angiography (UWFA) findings between dynamic and static images of eyes with diabetic retinopathy (DR).

METHODS

This cross-sectional study included 28 eyes of 28 patients with DR undergoing UWFA. A series of UWFA images acquired from each patient were converted into a time-lapse video and used as a dynamic image. A single, clear, arteriovenous phase image was chosen as a static image. Non-perfusion index (NPI) and its correlation with vascular abnormalities in different zones were compared between dynamic and static UWFA imaging.

RESULTS

NPI appeared to increase from the center to the far-periphery in both groups. Dynamic NPI was lower in the total retinal area (0.26 vs 0.29, P=0.009) and far-periphery (0.33 vs 0.36, adjusted P=0.042), which was contrary to the static NPI. Far-peripheral NPI was associated with intraretinal microvascular abnormality in the posterior area in both groups.

CONCLUSION

Time-lapse dynamic UWFA imaging is a useful modality to differentially diagnose hypofluorescence in the most peripheral region. This modality could provide a reliable method for NPI measurement.

Peripheral Capillary Non-perfusion in Birdshot Retinochoroiditis: A Novel Finding on Ultra-widefield Fluorescein Angiography

Purpose: To report a novel peripheral finding in patients with Birdshot retinochoroiditis (BRC) using ultra-widefield fluorescein angiography (UWFFA). Methods: UWFFA images from 90 patients diagnosed with BRC were reviewed. All images were evaluated for the presence of peripheral retinal ischemic changes and ischemia-related complications. Findings: Thirty-six eyes of 24 patients showed features of peripheral ischemia, including 18 eyes with peripheral capillary non-perfusion (CNP), 5 eyes with teleangectasias, with or without microaneurysms, and 13 eyes with both teleangectasias and CNP. None of the 36 eyes with peripheral ischemic changes developed retinal neovascularization following the diagnosis of peripheral ischemia. Conclusions: Peripheral ischemia may present in eyes with chronic inflammation as seen in BRC but does not seem to progress to neovascular complications. This is likely to be more common than suspected and has now become evident following the advent of UWFFA. Abbreviations: HLA-A29: Human leukocyte antigen - A29; FFA: Fundus fluorescein angiography; OCT: Optical coherence tomography; ICGA: Indocyanine green angiography; UWF: Ultra-wide field; UWFFA: Ultra-wide field fluorescein angiography; CNP: Capillary non-perfusion.

Reproducibility of Fixed-luminance and Multi-luminance Flicker Electroretinography in Patients With Diabetic Retinopathy Using an Office-based Testing Paradigm

BACKGROUND

We evaluated the reproducibility of office-based flicker electroretinography (ERG) in patients with nonproliferative diabetic retinopathy (NPDR).

METHODS

An observational study was conducted in which ultra-widefield fluorescein angiography (UWF-FA) was performed on 20 patients with mild-to-moderate NPDR; images were graded by the Fundus Photography Reading Center (Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, WI, USA). Fixed- and multi-luminance flicker ERG was repeated four times (greater than or equal to seven days apart). Recording consistency was assessed using intra-class correlation coefficients (ICCs), coefficients of variation, and Pearson correlations.

RESULTS

82.5% and 17.5% of eyes had mild and moderate NPDR using UWF-FA; 90% of the angiograms were given a high confidence grade. Fixed-luminance phase values were highly reproducible (ICC: 0.949; P < .001). There was a significant negative correlation between fixed-luminance phase and log-corrected ischemic index values (-0.426; P = .015).

CONCLUSIONS

Office-based, fixed-luminance phase values are highly reproducible and negatively correlate with retinal ischemia in NPDR, suggesting that global retinal dysfunction may be reliably quantified early in patients with diabetes.

Ultra-widefield angiography in the diagnosis and management of uveitis

PURPOSE

The aim of this study is to evaluate the clinical use of ultra-widefield angiography (UWFA) in uveitis.

MATERIALS AND METHODS

We showed the UWFA and traditional 55° fluorescein angiography (FA) of four cases with Eales' disease, idiopathic retinal vasculitis, aneurysms, and neuroretinitis syndrome, Behçet's disease, and idiopathic panuveitis in a tertiary medical center. Comparison of UWFA with traditional 55°FA in the diagnosis and management of uveitis and review of the literature is also presented.

RESULTS

Ultra-widefield FA revealed far-peripheral vascular imaging. This information would not have been easily obtained from traditional FA. With more information of the peripheral retina, it may facilitate appropriate diagnosis and monitoring, and the management may be revised.

CONCLUSION

University of Western Australia played an important role to confirm the diagnosis of uveitis and to determine the corresponding treatment.

Multimodal Imaging in Diabetic Macular Edema

Throughout ophthalmic history it has been shown that progress has gone hand in hand with technological breakthroughs. In the past, fluorescein angiography and fundus photographs were the most commonly used imaging modalities in the management of diabetic macular edema (DME). Today, despite the moderate correlation between macular thickness and functional outcomes, spectral domain optical coherence tomography (SD-OCT) has become the DME workhorse in clinical practice. Several SD-OCT biomarkers have been looked at including presence of epiretinal membrane, vitreomacular adhesion, disorganization of the inner retinal layers, central macular thickness, integrity of the ellipsoid layer, and subretinal fluid, among others. Emerging imaging modalities include fundus autofluorescence, macular pigment optical density, fluorescence lifetime imaging ophthalmoscopy, OCT angiography, and adaptive optics. Technological advances in imaging of the posterior segment of the eye have enabled ophthalmologists to develop hypotheses about pathological mechanisms of disease, monitor disease progression, and assess response to treatment. Spectral domain OCT is the most commonly performed imaging modality in the management of DME. However, reliable biomarkers have yet to be identified. Machine learning may provide treatment algorithms based on multimodal imaging.