Leber Congenital Amaurosis (LCA) is an inherited condition that causes poor vision. Findings commonly first appear after 2-3 months of age. LCA is caused by a defect in the cells that detect light in the retina (rods and cones).
It is rare (3 cases per 100,000 births). About 10-18% of all cases of congenital blindness or severely reduced vision in children are caused by LCA.
LCA is usually inherited in an autosomal recessive fashion. Both parents carry one copy of a recessive gene. If both parents are normal-sighted but carry the recessive gene, there is a 25% chance that each child will have LCA. A number of genetic defects have been found that cause LCA - most inherited in a recessive fashion. A rare form of dominant inheritance has been reported.
The most common early symptom is nystagmus (shaking of the eyes), and it is usually evident within the first few months of life. As a child gets older, poor vision/tracking, sensitivity to light and poking/rubbing of the eyes with a fist or finger may be noted. The ophthalmologist may see slow reaction of the pupils, hypermetropia that may require glasses, and abnormal appearance of the retina. There may be narrowing of the retinal blood vessels and optic disc may appear more pale than normal. Other less common findings include cataract, glaucoma, and cornea problems.
LCA is usually diagnosed by an ophthalmologist based on history and the physical findings on exam. An electroretinogram (ERG) is often utilized to test the function of the rods and cones of the retina and is performed with special equipment. Blood tests for genetic changes can sometimes help make the diagnosis in 50% of cases and help advise about the possibility of having some vision. It can also identify carriers of the condition among siblings and parents.
There are currently no treatments for most types of LCA. . Routine examinations by an ophthalmologist are recommended for all LCA patients to diagnose/treat other eye problems and prescribe glasses if necessary. Low vision aids to maximize visual function can be very useful for patients with LCA. Educational programs and support agencies for the visually impaired (and their families) are often quite helpful. There have recently been experimental successes using gene therapy for one type of LCA (RPE65 gene) in both animal models and humans, but this therapy is still in the research phase.
Best attainable vision is somewhat variable for people with LCA. Vision is typically 20/200 or less, while no light perception is uncommon. Vision sometimes improves slightly in the first years of life as the brain develops but usually plateaus or even deteriorates.
Most children with LCA are otherwise healthy. Neurologic, skeletal, muscular, heart, ear, and kidney abnormalities have been reported in a minority of LCA patients. If any of these are suspected, it is investigated in conjunction with the pediatrician. Most children with LCA have normal intelligence.
Currently there is a lot of research being done on LCA. Gene replacement therapy has been successful in animal models and in early, small studies in humans. However, while very promising, these results are still preliminary, and more studies are underway.
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