X-linked congenital stationary night blindness. Review and report of a family with hyperopia.

X-linked congenital stationary night blindness is almost always associated with myopia. We have reviewed all previously reported pedigrees and have found only two with patients without myopia. A recently proposed classification of night blindness includes a complete type associated with myopia and an incomplete type in which both hyperopia and myopia were found. Complete and incomplete types did not occur within the same pedigree. We report on a family in which three of the five affected members had hyperopia and could be classified as the incomplete type and in which a fourth member with myopia was more consistent with the complete type. The lack of myopia in three members of our pedigree can be explained by two hypotheses: crossing over of the night blindness and myopic genes on the X-chromosome, or an autosomal dominant hyperopic gene that masks the myopic gene. The data from our family support the first of these two hypotheses.