Disorders of pigmentation can result from either an abnormal number of melanocytes, as in nevus of Ota and vitiligo, or an abnormal amount of melanin production, as in albinism. Melanin-producing cells are found in the skin, mucous membranes, uveal tract, and retinal pigment epithelium of the eye and the stria vascularis of the inner ear. Thus, many of the hereditary or congenital pigmentary disorders of the skin are associated with similar pigmentary abnormalities in the eye, such as iris heterochromia or changes in pigmentation of the fundus; however, more commonly, the associated eye finding is a defect in ocular motility, i.e., strabismus and nystagmus, suggesting a concomitant defect in neurologic development. In albinos, the observed neurologic abnormality in the visual pathway and foveal hypoplasia are hypothesized to be related directly to the lack of melanin in the pigment epithelium during development. In acquired disorders of pigmentation, in particular, vitiligo, Vogt-Koyanagi-Harada syndrome, and onchocerciasis, there is a frequent association with uveitis, suggesting an inflammatory cause for the cutaneous pigmentary changes.