Heterozygote detection in X-linked recessive incomplete achromatopsia

Carrier women in a family with X-linked incomplete achromatopsia (XLIA) were evaluated by means of ophthalmologic examinations, psychophysical tests, and electroretinography (ERG). Ophthalmologic examinations of five obligate carrier women and three women at 50% risk were normal except for the finding of high myopia in one carrier and one woman at risk. Detailed color vision testing was normal in all eight women. By contrast, the corneal full-field ERGs of three of five obligate carriers and two of three women at risk displayed major, qualitatively similar abnormalities of their cone components that were readily detected by our quantitative method. These b-wave alterations were similar in all five women regardless of refractive error. Our findings suggest that the ERG can identify some women who carry the gene for this X-linked recessive condition who are normal by clinical and psychophysical testing.