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R. C. Baraas, L. A. Hagen, J. Neitz, M. Neitz; Tritan Color-vision Deficiency Associated with Novel Mutation in the Blue-sensitive Opsin. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2729.
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Five mutations in the S-cone-opsin gene that give rise to different single amino-acid substitutions (L56P, G79R, S214P, P264S, R283Q) have so far been reported to be associated with tritan color-vision deficiency. S-opsin mutations that cause autosomal dominant tritan deficiencies are analogous to rhodopsin mutations that cause autosomal dominant retinitis pigmentosa (adRP). The aim of this study was to determine the pattern of behavioral deficiency in a family with a novel mutation in the S-opsin gene.
Whole blood was obtained from each subject, and genomic DNA was extracted. The five exons that comprise the amino-acid coding region of the S-opsin gene were amplified by polymerase chain reaction (PCR) and sequenced. The subjects were classified with several clinical color-vision tests including the Farnsworth-Munsell 100-Hue test; HRR (4th edition, 2002) pseudoisochromatic plates; Moreland anomaloscopy and luminance matching (Oculus anomaloscope); and the Cambridge Colour test.
Eight individuals from one family have been identified to be heterozygous carriers of a mutation on the S-opsin gene: isoleucine for threonine at position 190. Five of eight have been tested so far, and all made tritan mistakes on color-vision tests. The younger ones show a milder degree of deficiency than the older ones, the same pattern of severity as that observed for the R283Q mutation (Baraas, et al. 2008 JOSAA 24:1438-1447).
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