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 mm2 /year, was similar to the average rate of RPE loss, 0.33 ± 0.38 mm2 /year. The average area of EZ loss at the initial examination, 4.18 ± 1.91 mm2 , was larger than the initial area of RPE loss, 2.25 ± 1.66 mm2 (P < .01). The absolute difference of the area of EZ loss on test-retest for the first grader was 0.12 ± 0.10 mm2 , and between graders 0.21 ± 0.21 mm2 . 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.