Purpose: This study measured and correlated degeneration of the junction between the inner and outer segments (IS/OS), the retinal pigment epithelium (RPE), and the choriocapillaris (CC) in Stargardt disease (STGD). Design: Prospective cross-sectional study. Methods: This study was conducted at the Casey Eye Institute. A total of 23 patients with STGD were enrolled and underwent optical coherence tomography angiography (OCTA). Scans were centered on the fovea. OCT slab projections and en face boundary maps were used to create masks to measure total IS/OS loss or RPE atrophy as well as regions of isolated IS/OS loss, isolated RPE atrophy, and matched IS/OS and RPE degeneration or intact IS/OS junction and RPE. CC vascular density (CCVD) was quantified from the CC angiogram. Outcomes included the area of loss, and the CCVD of degeneration in different areas was quantified and correlated. Results: The total area of IS/OS loss was strongly correlated with the total area of RPE atrophy (r = 0.96; P < 0.0001) by a 1.6:1 ratio (r2 = 0.90). CCVD within regions of matched degeneration (85.6% ± 2.7%; P < 0.0001), isolated IS/OS junction loss (93.6% ± 1.0%; P = 0.0011), and isolated RPE atrophy (94.1% ± 1.1%; P = 0.0065) were all significantly lower than normal (99.0% ± 0.17%). There was a trend for CCVD within intact areas (97.6% ± 0.38%) to decline as the area diminished (r = 0.68). Conclusions: Photoreceptor and RPE degeneration exhibited a strong relationship wherein the IS/OS loss was 1.6-fold greater than that of RPE atrophy, supporting the theory that photoreceptor degeneration precedes RPE in STGD. Both the photoreceptors and the RPE degeneration contributed synergistically to CCVD attenuation, but extralesional CCVD also tended to be abnormal. The findings and techniques in this study may be of utility in developing endpoints for clinical trials.
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