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Xiaofei Wang, Hongxin Song, Margaret Folwell, Lisa Latchney, Mina Chung; Adaptive Optics Scanning Laser Ophthalmoscopy Demonstrates Reduced Foveal Cone Density in Pattern Dystrophy. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1372.
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Pattern dystrophy (PD) is characterized clinically by lipofuscin deposition and atrophy in the retinal pigment epithelium (RPE); however, the RDS gene that causes PD encodes a protein localizing to the photoreceptor outer segments. The mechanism by which defects in RDS lead to the clinically detectable RPE disease remains poorly understood. In order to determine whether microscopic changes in the photoreceptors may precede clinically detectable RPE damage, we used adaptive optics scanning laser ophthalmoscopy (AOSLO) to study the foveal cones in a patient with PD.
A 55-year-old man with PD underwent complete eye examination and conventional imaging including fundus photography and fundus autofluorescence (FAF, Heidelberg Retinal Angiography). Genetic testing of the entire coding sequence of the RDS gene was performed using single-strand conformation polymorphism analysis and confirmed by automated DNA sequencing. AOSLO near-infrared reflectance images were obtained in square fields centered on the fovea and 10 x 1.5 degree montages of the photoreceptors of the inferior, superior and temporal retina were generated. Cones were counted in a 200x200 um window surrounding the fovea using custom semi-automated cone marking software.
Clinical examination showed 20/20 visual acuity with characteristic RPE changes in the peripheral macula, with sparing of the foveal center. Genetic testing showed a Tyr141Cys mutation in the RDS gene. AOSLO imaging showed a complete foveal cone mosaic with reduced peak cone density of 64 x 103 cones/ mm2 (normal 199 ±87 x103 cones/mm2).
These findings suggest that loss of foveal cone photoreceptors may precede the RPE changes that are detectable clinically in PD. As RDS-associated retinal disease is phenotypically heterogeneous, further study including more individuals is indicated.
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