Background and Purpose: Recent advancements in molecular biology have revealed genetic aspects of congenital color vision deficiencies (CVD). In many cases of CVD the genotypes and phenotypes coincide with each other. But it is also known that there are cases in which the genotype alone can not explain the clinical diagnosis of CVD. So it is still unclear whether routine gene analysis is useful as a clinical diagnostic tool for this anomaly. We evaluated the clinical usefulness of genetic analysis for congenital red-green color vision deficiencies.

Methods: The base sequences of red-green pigment genes of 42 CVD cases and 36 color normal males were determined using PCR and a DNA sequencer (ABI PRISM 300 Genetic Analyzer). The CVD cases were diagnosed using clinical color vision tests including an anomaloscope. The color normal subjects were tested with Ishihara plates and, if needed, with an anomaloscope.

Results: All normals had two types of exon 5, i.e., both red and green pigment genes. Thirty three (79%) of 42 CVD cases had only one type of exon 5, but 9 cases had both red and green types as did the normals. They could not be differentiated from the normals by exon 5 analysis. Of the 33 cases who had only one type of exon 5, three dichromats (IP and 2D) had two kinds of green pigment gene and one anomalous trichromats (PA) had only one type of red pigment gene. In all 13 cases (31%) had some inconsistencies between the genotype and the phenotype.

Conclusion: Pigment gene analysis alone could not fully differentiate CVD from normals.