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J. L. Duncan, Y. Zhang, S. M. Sundquist, A. Solovyev, S. Chang, N. Smaoui, A. Roorda; Structural Correlation Using Adaptive Optics Scanning Laser Ophthalmoscopy in X-Linked Retinoschisis. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5391.
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To study macular structure in a patient with X-linked retinoschisis (XLRS) with high-resolution imaging.
Best-corrected visual acuity (VA), fundus examination, automated perimetry and fundus-guided microperimetry, optical coherence tomography (OCT), fluorescein angiography (FA) and full-field electroretinography (ERG) were obtained. Molecular analysis of the RS1 gene was performed. Adaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) was used to generate high resolution montages of the macula.
A 29 year old man with VA of 20/50 OD and 20/63 OS demonstrated foveal schisis without leakage on FA and vitreous veils but no peripheral schisis cavities. Automated and fundus-guided perimetry showed relative scotomas within 5 degrees of fixation. OCT showed a large central cyst with schisis in the outer and inner plexiform layers. The mixed scotopic ERG b-wave was reduced to a greater extent than the a-wave, with a b/a ratio of 0.8. A hemizygous C duplication was present at nucleotide 579 in exon 6 (c.579dupC) in the RS1 gene. This mutation changed isoleucine to histidine at residue 194 (p.Ile194Hisfs) and is predicted to create a frameshift in the retinoschisin protein adding 75 amino acids. The right eye was chosen for AOSLO imaging. Cones and foveal schisis were readily observed across the 7 degree AOSLO image. The preferred retinal locus was displaced 2.5 degrees temporal, at the edge of a large central cyst involving the anatomic fovea. Within the cyst, cone spacing was increased (i.e., reduced cone density), corresponding to a dense scotoma on fundus-guided microperimetry. Outside of the large central cyst, cone spacing was similar to normal but visibility of the contiguous mosaic was disrupted by the edges of the schisis cavities.
AOSLO imaging demonstrated foveal schisis and cone structure in a patient with XLRS. Cone spacing was increased within a large cyst at the anatomic fovea, but nearly normal beginning at 2.5 degrees eccentricity. This study presents the first microscopic images of cones in a patient with a known mutation in the RS1 gene. Such images should provide a sensitive measure of the effect of this mutation on cone viability during the course of disease progression.
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