X-linked incomplete achromatopsia with more than one class of functional cones.

Five affected males in the fifth generation of a large pedigree of X-chromosomal incomplete achromatopsia were tested. All had SWS cone function. A 19-year-old affected man was a classical blue cone monochromat on color matching and spectral sensitivity. A 16-year-old boy showed evidence of a long wavelength sensitive cone active in 8 degrees color matches. With a blue-green background, his cone spectral sensitivity function peaked near 550-560 nm. Three younger boys, aged 7-10 yrs were evaluated only with color matching. All showed evidence of long wavelength cone function with an 8 degree field and one showed long wavelength cones in 2 degree matches. An independent observation concerning the family was the finding that deuteranomaly was introduced in the third generation. The fourth generation women, all obligate carriers of X-linked achromatopsia, had a 0.5 chance to carry deuteranomaly. Neither carrier state per se is usually associated with expression of deuteranomaly. Three of the five tested expressed deuteranomaly. This finding of deuteranomaly in the carrier females might be a consequence of a double carrier state indicating association between the genes for deuteranomaly and X-linked achromatopsia.