Correlation of Outer Retinal Degeneration and Choriocapillaris Loss in Stargardt disease using en face OCT and OCT Angiography.

PURPOSE: Measure and correlate degeneration of the inner segment/outer segment junction (IS/OS), retinal pigment epithelium (RPE) and choriocapillaris (CC) in Stargardt disease (STGD) DESIGN: Prospective cross-sectional study METHODS SETTING: Casey Eye Institute POPULATION: 23 patients with STGD PROCEDURES: OCT angiography (OCTA) scans were centered on the fovea. OCT slab projection 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, matched IS/OS and RPE degeneration, or intact IS/OS and RPE. CC vascular density (CCVD) was quantified from CC angiogram.

OUTCOME MEASURES: Area of loss and CCVD for different region types of degeneration were quantified and correlated.

RESULTS: The total area of IS/OS loss was strongly correlated with total area of RPE atrophy (r=0.96, p<0.0001) by a ratio of 1.6:1 (r2 =0.90). CCVD within regions of matched degeneration (85.6±2.7%; p<0.0001), isolated IS/OS 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 exhibit a strong relationship wherein IS/OS loss is 1.6 fold greater than RPE atrophy, supporting the theory that photoreceptor degeneration precedes RPE in STGD. Both photoreceptor and RPE degeneration contribute synergistically to CCVD attenuation, but extra-lesional CCVD also tended to be abnormal. The findings and techniques in this study may be of utility in developing endpoints for clinical trials.