Photoreceptor Layer Thinning over Drusen in Eyes with Age-Related Macular Degeneration Imaged In Vivo with Spectral-Domain Optical Coherence Tomography

Abstract

Purpose To detect changes in the neurosensory retina from spectral domain optical coherence tomography (SDOCT) imaging over drusen in age-related macular degeneration (AMD). Quantitative imaging biomarkers may aid in defining risk of progression and lead to better treatment options for AMD. Design Cross-sectional, case-control study evaluating SDOCT testing in AMD. Participants and Controls Seventeen eyes of twelve subjects with non-neovascular AMD and drusen and seventeen eyes of ten age-matched control subjects. Methods SDOCT imaging across the fovea in the study eye with multiple 10 to 12 mm scans of 1000 A-scans each. Main Outcome Measure In summed SDOCT scans, the height of individual retinal layers either over drusen or at corresponding locations in the control eye. Secondary measure: Photoreceptor layer (PRL) area, inner retinal area and retinal pigment epithelium (RPE)/drusen area. Qualitative changes in retinal layers over drusen. Results The PRL was thinned over 97% of drusen, the average PRL thickness was reduced by 27.5% over drusen compared to over a similar location in controls, and the finding of a difference was valid and significant (P=0.004). Photoreceptor outer segments were absent over at least one druse in 47% of eyes.. Despite thinning of the PRL, inner retinal thickness remained unchanged. We observed two types of hyper-reflective abnormalities in the neurosensory retina over drusen. First, distinct hyper-reflective speckled patterns occurred over drusen in 41% of AMD eyes and never in control eyes. Second, a prominent hyper-reflective haze was present in the photoreceptor nuclear layer over drusen in 67% of AMD eyes and more subtly in the photoreceptor nuclear layer in 18% of control eyes (no drusen). Conclusions With SDOCT as used in this study, we can easily detect and measure changes in PRL over drusen. Decreased PRL thickness over drusen suggests a degenerative process with cell loss leading to decreased visual function. The hyper-reflective foci overlying drusen are likely to represent progression of disease with RPE cell migration into the retina and possible photoreceptor degeneration or glial scar formation. A longitudinal study using SDOCT to examine and measure the neurosensory retina over drusen will resolve the timeline of these degenerative changes relative to druse formation.