Characteristics of Neovascularization in Early Stages of Proliferative Diabetic Retinopathy by Optical Coherence Tomography Angiography

Objective Evaluation of Proliferative Diabetic Retinopathy Using OCT

PURPOSE

To present the routine use of OCT and OCT angiography (OCTA) for the objective diagnosis and monitoring of proliferative diabetic retinopathy (PDR).

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Patients with diabetic retinopathy imaged using a standardized PDR protocol.

METHODS

Patients routinely imaged with a standardized PDR protocol between March 2017 and January 2019 were included. This included a 12×9-mm structural OCT volume centered on the macula and a 6×6-mm OCTA scan centered on the optic nerve head obtained using a Topcon swept-source system (DRI OCT-1 Triton, Topcon, Tokyo, Japan). Ultra-widefield fluorescein angiography (FA) was also performed when clinically indicated. The ground truth for each case was determined by merging the findings from biomicroscopy and imaging modalities to generate the maximum level of detection for each finding.

MAIN OUTCOME MEASURES

Detection rates of new-onset, regression, and reactivation of neovascularization of the disc (NVD) and neovascularization elsewhere (NVE) using different modalities (biomicroscopy/color photography, structural OCT, B-scan OCTA, en face OCTA). Detection of progression of tractional retinal detachment (TRD).

RESULTS

A total of 383 eyes of 204 patients were evaluated. After excluding patients without PDR or with insufficient image quality, 47 eyes of 35 patients were included. For the detection of new-onset NVD and NVE, structural OCT had the highest detection rate (100%) of all modalities. However, for the detection of regression or reactivation of neovascularization (NV), B-scan OCTA had the highest detection rate (100%). Structural OCT detected regression only in 45.5% of cases, resulting in a low detection rate of reactivation (12.5%). Among 10 eyes with TRD, OCT detected fovea-threatening TRD during follow-up in 7 eyes, resulting in vitrectomy.

CONCLUSIONS

This study demonstrates the utility of novel multimodal imaging in the daily management of patients with PDR. Posterior pole structural OCT had the best detection rate for NV, and B-scan OCTA showed the most potential for objective monitoring of disease after treatment.

Accuracy and Reliability in Differentiating Retinal Arteries and Veins Using Widefield En Face OCT Angiography

Purpose

To evaluate the accuracy and reliability in differentiating retinal arteries from veins using widefield optical coherence tomography angiography (OCTA).

Methods

Ten healthy eyes and 12 eyes from diabetic patients were included. Foveal-centered swept-source OCTA images (12 × 12 mm) were obtained using the PLEX Elite 9000. Vessels were graded as arteries or veins by two independent, masked readers. Arteriovenous crossings were also evaluated in healthy eyes. The vessel identification gold standard was defined using color fundus photographs (CFP) for normal eyes and both CFP and fluorescein angiography for diabetic eyes. Grading accuracy was compared to the gold standard and reliability between readers assessed.

Results

The study evaluated 538 vessels (119 first order, 110 second, 309 third) in healthy eyes and 645 vessels (184 first order, 159 second, 302 third). In healthy eyes, the average accuracies identifying all, first-, second-, and third-order vessels were 98.61%, 99.16%, 100%, and 98.06%, respectively. Cohen's κ between graders in all vessels was 0.948. In diabetic eyes, the average accuracies identifying vessels were 96.90%, 99.46%, 97.77%, and 94.85%, respectively. Cohen's κ between graders for all vessels was 0.888. For crossing identification, the average accuracy and Cohen's κ were low (60.71% and 0.659, respectively).

Conclusions

En face OCTA allows for accurate and reliable artery and vein identification; for small branches and crossings, identification by en face OCTA alone may be less accurate and reliable.

Translational Relevance

Arteries and veins can be differentiated on OCTA, assisting in clinically identifying pathology as arterial or venous side.

OCT angiography-based monitoring of neovascular regression on fibrovascular membrane after preoperative intravitreal conbercept injection

PURPOSE

To quantify the preoperative neovascular change pattern on the fibrovascular membrane (FVM) within 7 days after intravitreal injection of conbercept (IVC) using optical coherence tomography angiography (OCTA) in proliferative diabetic retinopathy (PDR).

METHODS

Prospective, observational study of PDR patients with visible FVM receiving or not receiving IVC. Neovascular changes were assessed by OCTA pre-IVC and 1, 3, 5, and 7 days post-IVC. Vessel skeleton density (SD) and vessel density (VD) were quantified by an intensity-based optical microangiography algorithm. The interclass correlation coefficient (ICC) was calculated to assess the agreement between measurements. The SD and VD were compared between follow-ups using repeated-measures analysis in the IVC group.

RESULTS

The ICC was 0.992 (95% confidence interval [CI]: 0.982-0.996) for SD and 0.926 (95% CI: 0.838-0.912) for VD of neovascularization. The neovascularization on FVM significantly regressed in the IVC group (n = 16) compared with no IVC (n = 8) (p = 0.001 for SD and p < 0.001 for VD). The comparisons between consecutive follow-ups showed a statistically significant reduction in SD and VD at 1 and 3 days post-IVC. However, from day 3 onward, the SD and VD remained unchanged. There was no development or progression of tractional retinal detachment within the 7-day period after IVC.

CONCLUSION

OCTA-based quantification of the neovascularization on FVM in PDR is feasible, with high inter-reader agreement. The regression of neovascularization reaches a plateau 3 days after IVC.

CLINICAL TRIAL REGISTRATION

This trial is registered with the Chinese Clinical Trial Registry ( http://www.chictr.org.cn , registration number ChiCTR-IPR-17014160).

Application of optical coherence tomography angiography in diabetic retinopathy: a comprehensive review

Optical coherence tomography angiography (OCTA) is a noninvasive method that enables visualization of blood flow within retinal vessels down to the size of capillaries by detecting motion contrast from moving blood cells. OCTA provides a fast and safe procedure to assess retinal microvasculature with higher contrast and resolution than conventional fluorescence angiography. The different capillary plexuses are displayed separately and their perfusion density can be quantified. Imaging capabilities such as these have led to an emerging field of clinical application for OCTA in vascular diseases such as diabetic retinopathy (DR). Evaluation of parameters such as parafoveal capillary perfusion density could be a biomarker for disease diagnosis and progression. Typical microvascular changes in DR such as capillary nonperfusion, microaneurysms, intraretinal microvascular abnormalities, and neovascularization can be reliably detected in optical coherence tomography angiograms, characterized in detail and attributed to the different capillary plexuses. Monitoring of these lesions in vivo gives potential novel insight into the pathophysiology in DR. The aim of this article is to summarize the potential applications/utility of OCTA in DR reported in the literature.

Familial retinal arteriolar tortuosity and quantification of vascular tortuosity using swept-source optical coherence tomography angiography

Purpose

Familial retinal arteriolar tortuosity (FRAT) is a rare autosomal dominant disorder that is characterized by tortuosity of the second and higher order retinal arterioles. We implement swept-source optical coherence tomography angiography (SS-OCTA) to quantify vessel tortuosity in patients with FRAT. We hypothesize that patients with FRAT will have higher retinal arteriole tortuosity when compared to controls.

Methods

Patients were scanned with a SS-OCTA device (Plex Elite 9000, Carl Zeiss Meditec, Dublin, CA). Images of a 12 × 12 mm² area centered on the fovea were processed, and retinal vessels >23.5 μm in diameter were identified. An automatic tortuosity measurement program written in MATLAB was used to assess vessel tortuosity. Branch points in the vessels were detected and used to separate the vasculature into individual segments. The tortuosity was measured by calculating the arc-chord ratio of each vessel segment, where a minimum value of 1 indicated a straight vessel and higher values corresponded to increasing tortuosity.

Results

Two patients (4 eyes) with a known history of FRAT and six controls (12 eyes) were enrolled in the study. The mean tortuosity of all vessel segments (MTVS) in scans of FRAT eyes was on average 1.1244 [range: 1.1044–1.1438] while for control eyes it was 1.0818 [range: 1.0746–1.0872]. Average MTVS of FRAT eyes was significantly higher compared to control eyes (p = 0.03).

Conclusions and Importance

Our results are consistent with the hypothesis that patients with FRAT have higher objective measurements of tortuosity compared to controls. Broader applications of this method may be of benefit in other retinal diseases with changes in retinal vessel configuration.