Leber congenital amaurosis
is an eye disorder that primarily affects the retina. People with this condition typically have severe visual impairment beginning in infancy. Other features include photophobia, involuntary movements of the eyes (nystagmus), and extreme farsightedness. The pupils also do not react normally to light. Additionally, the the cornea may be cone-shaped and abnormally thin (keratoconus). Franceschetti's oculo-digital sign is characteristic of Leber congenital amaurosis. This sign consists of poking, pressing, and rubbing the eyes with a knuckle or finger. At least 13 types of this condition have been described, which are distinguished by their genetic cause, patterns of vision loss, and related eye abnormalities. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.