Analysis of Choriocapillaris Flow Deficits Before and After Tears of the Retinal Pigment Epithelium using Swept Source OCT Angiography

Abstract

Purpose : Tears of the retinal pigment epithelium (RPE) occur in age-related macular degeneration (AMD) as part of normal disease progression or after injections with anti-VEGF. This provides opportunity to investigate two questions: does the presence of an intact pigmented RPE interfere with our ability to measure choriocapillaris (CC) flow deficits (FDs) and is the survival of the CC dependent on an intact overlying RPE. To answer these questions, we compared our CC FD measurements before and after a RPE tear and followed the change in CC FDs over time once the overlying RPE was removed.

Methods : Patients with AMD who developed RPE tears were enrolled in a prospective, swept source OCT (SS-OCT) imaging study and 6x6 mm scans centered on the fovea were acquired (PLEX^Ò Elite 9000, Carl Zeiss Meditec, Dublin, CA). Scans were obtained before and after the RPE tear formation, and during follow-up visits. CC FDs were measured at the site of the tear and within a control region symmetrically positioned to the fovea.

Results : Three AMD patients were followed before and after the RPE tear developed for 18 months. Two patients had a history of type 1 macular neovascularization and anti-VEGF therapy, and one patient had non-neovascular AMD. All three had macular CC FD that were previously determined to be within the 95% normal limits for age-adjusted eyes. When CC FD before the RPE tear were compared with those at the first post-tear visit, the average CC FD percentage decreased -0.7% in region of tear and -1.0% in control region (p=0.92, paired t-test). When CC FD from the first post-RPE tear visit were compared to 18-month follow-up visit, the average CC FD percentage decreased -1.9% in region of tear and increased +2.0% in control region (p=0.31, paired t-test).

Conclusions : SS-OCTA imaging of eyes with RPE tears indicate that there were no significant changes in CC FD before and after the RPE tears. Although the sample size was small, it appears that our CC algorithm for measuring FDs is reliable demonstrated by consistent measurements before and after the RPE was removed. Furthermore, removal of the RPE did not lead to significant changes in the CC over 18 months. This differs from animal studies demonstrating that RPE removal resulted in rapid loss of CC. The relationship between CC and RPE may not be absolute as previously believed.

This is a 2021 ARVO Annual Meeting abstract.