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M. Castelo-Branco, M. Mendes, A. Sebastião, A. Reis, Má. Soares, J. Saraiva, R. Bernardes, E. Silva; Novel Retinal Mechanisms Underlying Genetically Determined Neural Dysfunction in Williams-Beuren Syndrome. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5995.
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Williams-Beuren Syndrome (WS) provides a unique model to understand genetic determinants of visual cognition. Previous studies have suggested specific abnormalities on cortical visual information processing in WS, and defined a systems-level phenotype for visual deficits in this genetic condition, based on defective GTF2IRD1 expression and other genes, such as LIMK1. So far, only cortical dorsal stream abnormalities were considered to explain the visual phenotype in WS. Given the expression of these genes in the retina and role of GTF2IRD1 during eye development and outer layer differentiation we have aimed to demonstrate for the first time retinal impairment at different cell layers in WS.
We have used in vivo confocal ophthalmoscopy (Heidelberg Retinal Tomography), optical coherence tomography (Stratus OCT), and functional assessment in different regions of the retina with multifocal electrophysiology (using a RETIscan System), in 13 patients with clinically and genetically confirmed WS. All of our WS subjects had a similar 1.55 Mb hemideletion size.
Outer retinal thickness maps show a significant reduction when compared to age-matched controls. Morphometry of the optic nerve region revealed an abnormal pattern of anatomical organization of this region in WS patients. Multifocal electrophysiological recordings showed patterns of localized impairment of retinal responses in WS.
We have found novel mechanisms of retinal impairment in WS, which explain previously found perimetric deficits in contrast sensitivity, that have been hitherto unrecognized, and can be dissociated from high-level visual integration deficits.
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