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Jianfei Liu, Catherine A Cukras, Johnny Tam; Quantitative Analysis of Photoreceptor Swelling in Late-Onset Retinal Degeneration Using Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3168.
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© ARVO (1962-2015); The Authors (2016-present)
Late-onset retinal degeneration (L-ORD) is an autosomal disorder that leads to retinal pigment epithelium (RPE) and chorioretinal atrophy, with concomitant loss of photoreceptors. These changes appear to be preceded by lesions that are similar in appearance to reticular pseudodrusen (RPD). We hypothesize that photoreceptors are present above such lesions but are likely stressed due to dysfunction of the underlying RPE. Therefore, we investigate whether there are swollen cone photoreceptor inner segments above areas of RPD.
We used two modalities of adaptive optics scanning light ophthalmoscopy (AOSLO) to evaluate the photoreceptor layer across a range of eccentricities in both eyes of a 55-year-old patient with L-ORD (S163R mutation in C1QTNF5). Multimodality imaging, including confocal AOSLO was used to identify RPD lesions, and split-detection AOSLO was used to visualize cone inner segments. To quantify the size of individual cones, a semi-automated computer algorithm was developed to extract the boundary of inner segments, based on a circularly-constrained geodesic active contour. The effective diameter was then calculated and used as a measure of cone size.
In both eyes of this patient, RPD lesions were observed using confocal AOSLO at eccentricities less than 17 degrees, and could be distinguished based on their hyperreflective cores surrounded by hyporeflective annuli. Since RPD lesions appeared less discrete beyond this eccentricity, the quantitative analysis was restricted to areas within 17 degrees. Split-detection AOSLO confirmed the presence of cone photoreceptors overlying RPD, both in the hyperreflective core, as well as in the hyporeflective annuli. 349 cones were identified above 114 lesions, along with 669 cones identified in non-lesion areas at matching eccentricities. Effective cone diameters varied depending on the eccentricity (Table 1), but were consistently enlarged above lesion areas when compared to non-lesion areas (p<0.05, paired t-test). Overall, cone inner segments were swollen above RPD with an average effective diameter increase of 20%.
Cone photoreceptor cells can survive above RPD, but undergo swelling which can be detected using adaptive optics. This swelling might be useful as a biomarker for retinal disease, with potential application to other diseases in which RPD manifest, such as age-related macular degeneration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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