Quantifying the Rate of Ellipsoid Zone Loss in Stargardt Disease

PURPOSE: To determine a reliable method of using the ellipsoid zone (EZ) on optical coherence tomography (OCT) to track disease progression in Stardgardt disease (STGD). DESIGN: Retrospective reliability study. METHODS: STGD patients with genetically confirmed ABCA4 gene mutations seen at the Wilmer Eye Institute with follow-up visits separated by at least 12 months were identified. Spectral-domain optical coherence tomography (SD-OCT) macula volume scans centered at the fovea and fundus autofluorescence (FAF) images were obtained. The area of EZ loss was calculated from the SD-OCT and the area of retinal pigment epithelium (RPE) loss from the FAF. Scans were reanalyzed by the primary grader to assess intragrader reliability, and reanalyzed by a second grader to assess intergrader reliability. RESULTS: Sixteen STGD patients (total of 31 eyes) were followed for a mean of 2 years (range 1-4.7 years). The mean rate of EZ loss, 0.31 +/- 0.31 mm(2)/year, was similar to the average rate of RPE loss, 0.33 +/- 0.38 mm(2)/year. The average area of EZ loss at the initial examination, 4.18 +/- 1.91 mm(2), was larger than the initial area of RPE loss, 2.25 +/- 1.66 mm(2) (P < .01). The absolute difference of the area of EZ loss on test-retest for the first grader was 0.12 0.10 mm(2), and between graders 0.21 +/- 0.21 mm(2). The intraclass correlation (ICC) of both intragrader and intergrader reliability for EZ loss was excellent at 0.99. CONCLUSIONS: Tracking the area of EZ loss on SD-OCT macular volume scans longitudinally is a reliable way of monitoring disease progression in STGD. This could be used as a sensitive anatomic outcome measure in clinical trials related to STGD. (C) 2017 Elsevier Inc. All rights reserved.