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Grace Han, Yusufu N B Sulai, Albert M Maguire, Jean Bennett, Alfredo Dubra, Jessica Ijams Wolfing Morgan; Adaptive optics imaging of ABCA4 Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2616.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize disease pathogenesis in Stargardt Retinal Dystrophy through high resolution confocal adaptive optics (AO) retinal imaging.
10 Stargardt patients aged 11-64 with ABCA4 genetic mutations were imaged using AO scanning light ophthalmoscopy (AOSLO) (Canon, Inc and/or a custom system), spectral domain optical coherence tomography (OCT) (Heidelberg Spectralis), autofluorescence (AF), fundus photography, wide-field P200C-AF (Optos, PLC) and fundus guided photopic microperimetry (Nidek MP1). Longitudinal AOSLO imaging was performed in two patients, at 10 and 24 months. Images from all modalities were co-registered in Photoshop. Cell density was measured in AOSLO images using a semi-automated Matlab script. Cell diameters were measured manually.
AF imaging revealed retinal pigment epithelial (RPE) atrophy in all patients including hypo-AF patches of RPE loss in central retina, with hyper-AF macular flecks (7/10 patients) and/or a hyper-AF ring surrounding the central atrophic region (4/10). Wide-field SLO showed the RPE atrophy and abnormal AF was confined to the central retina in all but 2 patients, one which exhibited hyper-AF mottling into the far periphery, and another with atrophy in the far temporal retina. Foveal sensitivity was reduced in all patients by at least 3dB, only 2 patients did not exhibit an absolute scotoma (sensitivity reduced by more than 2 log units) within 1mm of the fovea. 6 patients fixated foveally; 4 patients fixated with superior retina. In 4 patients who fixated foveally, AOSLO imaging revealed a contiguous foveal cone mosaic with substantially enlarged cones and reduced cone density (p<0.001). Qualitatively, cones observed eccentric to the fovea also appeared enlarged; however, quantitative cell density measurements many times produced results within or above normal cone density measures. Photoreceptor layers were present at these same locations on OCT.
AOSLO imaging allows single cell analysis in ABCA4 retinal degeneration. Cone loss and enlargement can be observed at the fovea and occurs in parallel with changes in the RPE lipofuscin content. At eccentricities outside of the fovea, cell loss and enlargement may occur in both cone and rod photoreceptors - further study is needed to confirm this hypothesis. Future studies will further delineate pathogenesis in ABCA4 disease.
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