Disruption of Cone Photoreceptors Observed Using Adaptive Optics Retinal Imaging in Spinocerebellar Ataxia Type 7 (SCA7)

Abstract

Purpose : Adaptive optics retinal imaging (AO) allows for detailed observations of the human retina. Thus, using this technology in early stages of Spinocerebellar Ataxia Type 7 (SCA7), a genetic neurodegenerative disease that causes significant vision loss, may give insight into the early signs of retinal involvement. In this study, we used AO alongside clinical assessments to evaluate the cone photoreceptors and retinal pigment epithelium (RPE) in patients with SCA7.

Methods : Using a custom built multimodal AO imager, the cone photoreceptor and RPE layers were imaged in both eyes of three patients with molecularly confirmed SCA7. Cones were imaged using both confocal reflectance and non-confocal split detection, and RPE using AO enhanced indocyanine green in the late phase. Evaluation of both layers early in the disease was performed by co-registering AO images, color fundus photography, and microperimetry (MP1) assessments. Cells within regions of interest from AO images near points of functional visual testing (MP1) were semi-automatically identified for quantification.

Results : AO imaging revealed a patchy pattern of cone photoreceptors interspersed among surrounding areas with contiguous mosaics of cones. Overall, the RPE mosaic did not appear to be affected. Quantitative analysis of cone spacing revealed that there were areas of increased cone spacing in both patchy and contiguous areas. There was a negative correlation between the percentage increase in cone spacing relative to histology vs. MP1 measures, suggesting that there is a relationship between structural and functional assessment in the early stages of SCA7 (OD: r²=0.55, p<0.001; OS: r²=0.43, p<0.001). In the fovea, where the patchy pattern of cone photoreceptors was most likely to be observed, RPE spacing was within normal limits.

Conclusions : Herein we present the first AO images of patients with SCA7 and we provide evidence that in early stages of SCA7, the cone photoreceptor layer is impacted earlier than the RPE. This study demonstrates that AO imaging can be used as guidance to assess the early stages of SCA7 maculopathy.

This is a 2020 ARVO Annual Meeting abstract.