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Spring 2001 Table of Contents
Versión Español de este artículo (Spanish Version)
By Kate Moss, Family Specialist, TSBVI, Texas Deafblind Outreach
I have recently received a number of requests for information about Leber's Congenital Amaurosis, a degenerative disease that results in a severe loss of vision. This disease is thought to be caused by abnormal development of photoreceptor cells in the retina or perhaps the extremely premature degeneration of the retinal cells. Typically a baby with LCA will have very reduced vision at birth although the retina may appear normal when first examined. Within months, however, parents will usually notice nystagmus - an involuntary, rhythmical, repeated movement of the eyes. Children with LCA account for 10-18% of all cases of congenital blindness. Vision in individuals with LCA varies greatly from relatively mild acuity problems (20/70) to no light perception. (Leber's Links, 2001)
Occasionally LCA may be confused with other retinal problems such as retinitis pigmentosa, congenital and hereditary optic atrophy, cortical blindness, congenital stationary night blindness, flecked retinal syndrome, and achromatopsia. (Foundation Fighting Blindness, 2001) Some children originally diagnosed with LCA were later discovered to have Joubert Syndrome, Alstrom Syndrome, and Senior-Loken Syndrome. Although hearing loss is not an identified feature of LCA, some children with LCA in Texas also have hearing impairments. The 2000 Texas Deafblind Census identified ten such individuals and the 2001 Census identifies seven with both LCA and hearing loss. Some of these children were initially misdiagnosed as having Usher Syndrome.
LCA is genetically passed through families, and both parents must be carriers. Each parent has one gene with the disease, paired with one gene that is normal. When each child is conceived he will inherit genes in one of four ways. (1) If he gets the two healthy genes from his parents, he does not have LCA and is not a carrier. (2 & 3) If he gets a disease gene from one parent and not the other, he will be a carrier but not have the symptoms of LCA. (4) If he gets the two disease genes from his parents, he will have LCA. This is referred to as an autosomal recessive pattern of inheritance.
Children with LCA often have eyes that appear sunken or deep set. They may press on the eyes frequently; this is called oculo-digital reflex. Some children with LCA have cone-shaped corneas (Keratoconus) and cataracts that cause the corneas to become cloudy. By the time a child reaches adolescence, pigmentary changes occur in the retinal pigment epithelium (the supportive tissue underneath the retina). This is similar to changes that occur to the retina with retinitis pigmentosa, the vision condition associated with Usher Syndrome. This occurs because the blood vessels in the retinas become narrow and constricted. Unlike Usher Syndrome, where a progressive loss of vision is typical, vision loss in individuals with LCA usually remains stable through young adult life. Progression of vision loss later in life has not yet been clearly defined. Additionally, some individuals with LCA are very sensitive to light (photophobic). Children with some remaining vision are likely to be extremely farsighted as well. (Foundation Fighting Blindness, 2001)
In some cases, individuals with LCA also show central nervous system complications. They may be developmentally delayed, have seizure disorders, or motor impairments.
There is currently no treatment for LCA. However, there is a
good deal of genetic research being done related to LCA. The
Foundation Fighting Blindness notes that a gene for LCA has been
isolated on chromosome 17. The Leber's Link website offers
information from The Johns Hopkins Center for Hereditary Eye
Diseases that indicates three genes associated with LCA:
chromosome 17, a 65kD RPE protein, and CRX on chromosome 19. A
fourth gene has recently been localized for this disease. In
Texas, Dr. Richard Lewis with Baylor College of Medicine is doing
ongoing research on LCA. Dr. Lewis is open to contact from
families of children with LCA or who suspect their child of
having LCA. Another contact at Johns Hopkins is Irene Maumenee.
Contact information for both Dr. Lewis and Dr. Maumenee is listed
Dr. Richard Lewis, MD/MS
Professor, Department of Ophthalmology, Pediatrics, Medicine and Molecular and Human Genetics
Cullen Eye Institute, NC-206
One Baylor Plaza
Houston, TX 77030
Phone: (713) 798-3030
Irene E. Maumenee, MD
Professor of Ophthalmology, Medicine and Pediatrics
Wilmer Eye Institute
Maumenee Building, Suite 517
The Johns Hopkins Hospital
600 North Wolfe Street
Baltimore, MD 21287-9237
Phone: (410) 955-5214
If you are interested in connecting with other families concerned with LCA, there are a number of good websites available to help you with this. They also are a good resource for updates on research and general information about LCA.
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Last Revision: October 25, 2004