Vision Function of Rod Monochromats: I. Advanced Clinical Measures

Abstract

Achromatopsia -- the absence of color vision -- is a relatively rare condition which can result from a variety of congenital and acquired ocular disorders. The most common form of achromatopsia is complete (typical) rod monochromatism, which is inherited as an autosomal recessive trait and is characterized by severely reduced visual acuity, pendular nystagmus and photophobia. X-linked recessive incomplete (blue cone) monochromatism, in which the patient has both rod and blue cone function, has a very similar presentation clinically, and is often confused with complete rod monochromatism. Less common etiologies include autosomal recessive incomplete achromatopsia (red or green cone function only) and a number of acquired cone and rod-cone dystrophies and degenerations; any of these conditions may present with varying degees of color vision loss, acuity loss, photophobia and nystagmus. From a clinical standpoint, the correct diagnosis of an achromat is necessary for appropriate patient managment and, with hereditary forms, genetic counseling. Yet most practitioners base their diagnosis of rod monochromacy on a minimal amount of information.