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Sarim Mohammad, Anil Kumar, Mervyn Thomas, Christopher Degg, Viral Sheth, Irene Gottlob, Frank A. Proudlock; The Functional Significance Of Foveal Abnormalities In Albinism Measured Using Spectral-domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2989.
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The relationship between foveal abnormalities in albinism and best corrected visual acuity (BCVA) is unclear. We used high resolution spectral-domain optical coherence tomography (SD-OCT) to assess the functional significance of foveal morphology in patients with albinism.
7x7x2mm volumetric scans of the fovea were acquired using high resolution SD-OCT (3µm axial resolution) in 47 patients with albinism. The B-scan nearest to the centre of the fovea was identified using signs of foveal development such as presence of a rudimentary pit, thinning of the inner retinal layers, doming of the outer nuclear layer and lengthening of the photoreceptor outer segments. The thickness of each retinal layer at the fovea and foveal pit depth was quantified manually using ImageJ software and compared to best corrected visual acuity (BCVA).
Total photoreceptor layer thickness at the fovea was highly correlated to BCVA (p<<0.0001, r=-0.550). Of the photoreceptor layers, outer segment length (OSL) was most strongly correlated to BCVA (p<0.0001, r=-0.595). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (p>0.05). This was due to an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (p<<0.0001, r=-0.690).
Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit as patients with similar overall retinal thickness had widely varying foveal morphology. In albinism we find the size of the photoreceptor outer segment to be the strongest predictor of BCVA. Our results suggest that detailed SD-OCT images of photoreceptor anatomy provided a useful tool in assessing the visual potential in patients with albinism.
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