Feasibility of ellipsoid zone quantification as identified on optical coherence tomography using a customized software algorithm in the clinical trial of Allogeneic Human Retinal Progenitor Cells (hRPC) for the Treatment of Retinitis Pigmentosa.

Abstract

Purpose : To describe the feasibility of ellipsoid zone quantification on spectral domain optical coherence tomography in a clinical trial assessing the treatment of retinitis pigmentosa (RP).

Methods : A customized OCT platform using logic based identification of OCT layers was utilized. 97 line macular spectral domain OCT scans (Heidelberg) obtained at baseline visits on 25 patients were analyzed using this software. OCT layers were then identified and manually corrected by trained graders. Ellipsoid zone (EZ) metrics were then calculated including thickness and volume. EZ thickness maps were also created.

Results : 29 eyes from 29 subjects with advanced RP (mean BCVA 1.02logMAR or 34 letters; mean age 46) were included. All eyes were successfully mapped and graded. Logic based identification successfully identified more normal areas of EZ, but required manual correction often in areas of severe EZ loss. The mean central subfield thickness was 206.53 µm. The mean EZ-RPE central subfield thickness was 11.35 µm (range 0.76 – 37.04 um) Mean EZ-RPE volumetric measures of the central subfield, mid subfield and macula were 0.0089 mm³, 0.025 mm³ and 0.087 mm³ respectively. En face zero micron and less than 20 micron EZ-RPE thickness coverage maps of the macula were created. The mean zero micron coverage within the macula was 84.36% (range 59-98%); the mean less than 20 micron thickness was 96% (range 84-100%).

Conclusions : This study provides important insight into the use of OCT EZ-RPE analysis for advanced RP. EZ-RPE thickness and volume was measurable, but required manual correction. In contrast to normal OCTs (0.87% mean attenuation with a mean of 0.12% total attenuation), significant EZ attenuation occurred in RP subjects with marked loss noted beyond the midsubfield (central 2 mm) area. OCT analysis of the EZ layer provides important information about the severity of photoreceptor loss in retinitis pigmentosa.

This is a 2021 ARVO Annual Meeting abstract.