Longitudinal Assessment of the Choroidal Vascularity Index in Eyes with Branch Retinal Vein Occlusion-Associated Cystoid Macular Edema

Abstract

Introduction: Cystoid macular edema (CME) is the most common cause of central vision loss in eyes with branch retinal vein occlusion (BRVO eyes). In recent literature, choroidal vascularity index (CVI) has been proposed to be an enhanced depth imaging optical coherence tomography (EDI-OCT) metric that may help characterize choroidal vascular changes in the setting of retinal ischemia, and potentially prognose visual outcomes and treatment patterns for patients with BRVO-related CME. This study sought to further characterize choroidal vascular changes in BRVO by comparing the CVI, subfoveal choroidal thickness (SFCT), and central subfield thickness (CST) in BRVO eyes with CME compared to unaffected fellow eyes.

Methods: This was a retrospective cohort study. Subjects included treatment-naïve BRVO eyes with CME diagnosed within 3 months of onset of symptoms and unaffected fellow eyes. EDI-OCT images were collected at baseline and at the 12-month follow-up visit. CVI, SFCT, and CST were measured. Demographics, treatment patterns, and best-corrected visual acuity (VA) were abstracted. Median CVI, SFCT, CST, and VA were compared between the two cohorts. Longitudinal relationships between these variables were analyzed.

Results: A total of 52 treatment-naïve eyes with BRVO and CME and 48 unaffected fellow eyes were identified. Baseline CVI was lower in eyes with BRVO than in fellow eyes (64.7% vs. 66.4%, P = 0.003). At 12 months, there was no difference in CVI between BRVO eyes and fellow eyes (65.7% vs 65.8%, P = 0.536). In BRVO eyes, there was a strong correlation between reduced CST and improved VA over the 12-month study period (r = 0.671, P < 0.001).

Conclusion: There are differences in CVI in treatment-naïve BRVO eyes with CME at presentation compared to fellow eyes, but these differences resolve over time. Anatomic changes in macular thickness in BRVO eyes with CME may be correlated with VA outcomes.

Keywords: Branch retinal vein occlusion; Choroidal vascularity index; Cystoid macular edema; Optical coherence tomography.

Fig. 1

Illustration of the Comprehensive Ocular Imaging Network (COIN) console for computing the choroidal vascularity index (CVI) in eyes with macular edema. a Unsegmented original optical coherence tomography (OCT) scan. b The region of interest (ROI) created by the grader with help of automation for ROI wherein the retinal pigment epithelium–Bruch's membrane (RPE-Bruch) complex (upper limit of ROI) and choroidal scleral interface boundary (lower limit of ROI) can be manually adjusted at the grader’s discretion based on case-by-case assessment of the OCT scan. c Automated thresholding and binarization of the ROI to give the demarcation between luminal areas (LA) and stromal areas (SA) within the segmented choroid (ROI). d The reader panel of the console presenting the different values generated by the COIN platform after the image is binarized. It gives the option to fix the scale for conversion of pixels to microns and provides values of choroidal thickness (CT), CVI, total choroidal area (TCA), luminal area (LA), and stromal area (SA) for the left, mid, and right segments of the choroid. It also provides the grader with the ability to alter the span of the ROI and option of 1-click ACN (approve, collect results, and move to next image) to facilitate faster image analysis

Fig. 2

Correlation between change in central subfield thickness (CST; in μm) and change in VA (logMAR) in BRVO eyes over the 12-month study period (r = 0.671, P < 0.0001). RVO Retinal vein occlusion