Histologic Photoreceptor and Retinal Pigment Epithelium Degeneration in an Eye With Clinically Documented Geographic Atrophy of AMD

Purpose: In geographic atrophy (GA) of AMD, comparing photoreceptor disintegrity and RPE loss in optical coherence tomography (OCT) and microscopy may elucidate atrophy expansion and suggest imaging biomarkers. Methods: One eye of a 93-year-old woman with bilateral drusen-driven GA of AMD was analyzed. RPE loss and reduced photoreceptor segment integrity (rPSi) was quantified automatically in clinical OCT volumes over a five-year period ending six years pre-mortem. In transmission electron micrographs of the outer junctional zone (OJZ) and a comparison area, tissue component volumes were measured. Results: By OCT, rPSi area exceeded RPE loss at baseline. Yearly RPE loss (2.432 mm2) exceeded rPSi (1.770 mm2) as these areas converged. By microscopy, the mean distance between the external limiting membrane (ELM) and RPE basal lamina in the OJZ was 50% of the comparison. Volumes of interphotoreceptor space, outer segments, inner segment myoids, inner segment ellipsoids, and in-layer RPE were 16%, 17%, 25%, 50%, and 104%, respectively, of the comparison. Cone inner segments exhibited fragmented and translocating mitochondria over drusen and at the ELM descent. In some OCT scans, the descent appeared especially hyperreflective. Conclusions: In this first clinicopathologic correlation of an AMD eye with a known GA growth rate, the area of rPSi (a composite representing photoreceptor shortening, disorganization, altered waveguiding, and true cell death) exceeds the area of RPE loss. The OJZ exhibits dysmorphic but continuous RPE. Photoreceptors degenerate from the outer segments inward. Mitochondrial fission and translocation at the ELM descent may be visible clinically.