Contrast sensitivity function in nephropathic cystinosis.

Cystinosis is a rare autosomal recessive metabolic disorder in which nonprotein cystine accumulates within most body organs due to a defect in lysosomal cystine transport. The pathognomonic ocular manifestations of cystinosis are the presence of distinctive iridescent crystals within ocular tissue and a pigmentary retinopathy. We measured spatial contrast sensitivity in seven patients with infantile-onset nephropathic cystinosis and compared their contrast sensitivity function with that measured in ten age-matched controls. Spatial contrast sensitivities in the patient group were significantly lower than those in the normal group. Loss of contrast sensitivity in the patients with nephropathic cystinosis was more pronounced at higher spatial frequencies. We speculate that this loss of contrast function is primarily a manifestation of corneal disease, with secondary contributions from retinal changes and central nervous system dysfunction.