Abstract
Purpose :
To assess histologic components of the fourth outer retinal band of optical coherence tomography (OCT), we measured retinal pigment epithelium (RPE), basal laminar deposit (BLamD), and Bruch’s membrane (BrM) thicknesses at different AMD stages.
Methods :
Donor eyes were processed for macula-wide, high-resolution histology (http://projectmacula). At predefined foveal and parafoveal locations, RPE, BLamD, and BrM thicknesses were measured and RPE phenotypes assigned. AMD stages were assigned histologically (RPE dysmoprhia with drusen and basal linear deposit): unremarkable (UR, n=55), early-intermediate nonneovascular AMD (NNV, n=23), geographic atrophy (GA, n=13), and neovascular AMD (NV, n=41).
Results :
For non-atrophic RPE, average RPE thickness did not change as a function of diagnostic class (UR 12.8 ± 2.4; NNV 11.7 ± 4.8; GA 12.1 ± 5.14; NV 14.4 ± 8.34). Eyes with GA or NV AMD had more variable RPE thicknesses and RPE phenotypes. UR eyes had a lower percentage of cells with dysmorphic phenotypes compared to eyes with NNV AMD. BLamD thickness increased between UR eyes and NNV eyes, even after controlling for RPE phenotype (UR 0.88 ± 2.1, NNV 5.41 ± 6.6). BLamD thickness did not differ between donors with NNV AMD and those with NV AMD or GA (NNV 5.41 ± 6.6, GA 5.4 ± 6.29, NV 4.86 ±6.06). BrM was thinner in eyes with NV AMD compared to all other groups.
Conclusions :
As AMD progresses, RPE thickness becomes increasingly variable, reflecting multiple pathways of RPE death. Because some pathways involve thinning of RPE and others thickening, average RPE thickness does not fully capture progression. Even after controlling for RPE phenotypes, BLamD was thicker in NNV eyes than in UR eyes, suggesting BLamD or RPE+BLamD as a OCT biomarker in assessing this transition. Findings are consistent with those of Sarks, who used BLamD to stage AMD histologically in 1976.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.