Leber congenital amaurosis

Leber congenital amaurosis (LCA) primarily affects the retina, the specialized tissue at the back of the eye that detects light and color. Beginning in infancy, people with LCA typically have severe visual impairment. This is most often non-progressive, but sometimes it very slowly worsens over time. Other vision problems associated with LCA include:^[1][2]

• Photophobia
• Nystagmus
• Clouding of the lens of the eyes (cataract)
• Crossed eyes (strabismus)
• Enophthalmos (eye balls are dislocated backward)
• Abnormal retinal pigment
• Extreme farsightedness (hyperopia)
• Pupils that may not react normally to light; they may expand and contract more slowly than normal, or they may not respond to light at all
• Keratoconus, a condition in which the cornea is cone-shaped and abnormally thin, may also be present

A specific behavior called Franceschetti's oculodigital sign is characteristic of LCA. This behavior consists of poking, pressing, and rubbing the eyes with a knuckle or finger. It may possibly contribute to deep-set eyes and keratoconus in affected children.

In rare cases, delayed development, hearing loss, and intellectual disability have been reported in people with the features of LCA. However, it is unclear whether these people actually have LCA or another syndrome with similar signs and symptoms.^[3]

The first signs of LCA typically become apparent in infancy when parents notice a lack of visual responsiveness and unusual eye movements in the affected child. The child's retinas may appear normal during an eye examination at this time, but electroretinography (ERG) tests, which measure visual function, will typically detect little (if any) activity in the retina.

By early adolescence, various changes in the retinas usually become apparent. Blood vessels often become narrow and constricted, and a variety of color changes can also occur in the retinal pigment epithelium. Although the appearance of the retina undergoes significant change with age, vision usually remains fairly stable through young adult life. However, the long term visual prognosis remains unknown.^[4]

Some studies suggest that as many as 20% of children with LCA without associated anomalies develop intellectual disability. Whether these individuals represent undiagnosed systemic disorders or a genetic subtype of LCA is still unknown.^[1]