Blue Cone Monochromatism: Clinical Findings in Patients with Mutations in the Red/Green Opsin Gene Cluster
Kellner U.1, Wissinger B.2, Tippmann S.2, Kohl S.2, Kraus H.1, Foerster M. H.1
1Dept. of Ophthalmology, UKBF, Free University Berlin, 2Molecular Genetics Laboratory, Dept. of Ophthalmology, University Clinic, Tuebingen
Purpose: X-linked blue cone monochromatism is an important differential diagnosis in cone dysfunction and has to be separated from cone dystrophy and autosomal recessive rod monochromatism.
Method: In 7 male patients with congenital cone dysfunction (1 family and 4 single cases; age range 9-55 years) mutations in the red/green opsin cluster were confirmed. Clinical findings were analysed retrospectively.
Results: In 6/7 patients a single red/green hybrid opsin gene was found that harboured the known pathogenic Cys203Arg mutation. In one patient a large deletion of the locus control region was detected. Two patients (age 45 and 55 years) complained about progression. Only one patient presented with nystagmus. Refractive errors varied between +8.0 and 11.0 D. Visual acuity was between 0.05 and 0.3, but only 3 patients had a visual acuity better than 0.1. In one patient visual acuity could be improved using blue filter glasses. All 4 patients older than 25 years had dystrophic alterations in the macula. Sever color vision defects and relative central scotoma were present in all patients. In the ERG (6/7 patients) residual cone responses were detected in 2 pat
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