1Optometry & Visual Science, Buskerud University College, Kongsberg, Norway
2Department of Ophthalmology, The Medical College of Wisconsin, Milwaukee, Wisconsin
ADepartment of Ophthalmology, BCenter for Visual Science, 3University of Rochester, Rochester, New York
4School of Electrical and Electronic Engineering, University of Manchester, Manchester, United Kingdom
Commerical Relationships: R.C. Baraas, None; J. Carroll, None; K.L. Gunther, None; M. Chung, None; D.R. Williams, None; D.H. Foster, None; M. Neitz, None.
Support: This work was supported by the Wellcome Trust (Grant No. 064669/Z/01/Z), NIH (Grant No. EY04367, EY09303 and EY09620, and F32EY014789 (KLG)), and by Research to Prevent Blindness.
Purpose:Tritan color-vision deficiency is an autosomal dominant disorder associated with amino-acid substitutions in the S-cone-pigment gene that are predicted to perturb the structure or stability of the S-cone pigment. The aim of this work was to determine whether the loss of S-cone function is accompanied by physical disruption of the cone mosaic.
Methods:An adaptive-optics ophthalmoscope was used to image the cone mosaic of a 56-year-old male and his 33-year-old daughter, each having a novel mutation (R283Q) in one of their S-cone pigment genes. The density and regularity of the cone mosaic of each subject was compared with that of normal controls. Subjects also performed standard color-vision tests and surface-color matching under different illuminants.
Results:The fathers behavior on all color-vision tests was characteristic of a tritanope, whereas the daughter made only mild tritan errors. His surface-color judgments were also characteristic of a tritanope. Retinal imaging revealed different S-cone mosaics consistent with their discrepant phenotypes: no evidence for S cones was found in the retinal images from the father, whereas the daughter had normal S-cone density. Voronoi and nearest-neighbor analyses showed that the fathers mosaic was significantly more irregular than of normal controls.
Conclusions:The absence of S-cones coupled with the abnormal packing arrangement of the remaining cones in the 56-year-old tritan suggests that heterozygosity for the R283Q mutation ultimately results in the death of S-cones. It is hypothesized that the phenotypic difference between the father and daughter with the same mutation is due to their being at different stages in a progression where dominant negative interactions compromise the function and viability of S-cones.
Keywords: color vision retinal degenerations: hereditary imaging/image analysis: clinical
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