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What is Leber Congenital Amaurosis?
Leber Congenital Amaurosis (LCA) is a group of inherited diseases that are characterized by severe vision loss at birth that progress to blindness in early adulthood. The incidence of LCA is rare and has been estimated at 1 out of 80,000 births in the U.S. and 3 out of 100,000 newborns worldwide, but accounts for approximately 20% of children in schools for the blind.
What causes LCA?
To date, there are 14 gene defects that have been found to cause LCA. These mutations account for 75% of all LCA cases. The cause for the remaining 25% remains unknown.
There are 2 subtypes of LCA that are of interest to QLT, those due to defects in retinal pigment epithelial protein 65 (RPE65) and lecithin-retinol acyltransferase (LRAT) genes, which are part of a biochemical pathway called the visual cycle. The visual cycle is responsible for supplying the rod and cone cells of the retina with a chemical called 11-cis-retinal. When these genes are defective 11-cis-retinal is not produced at adequate levels. Without 11-cis-retinal the rods and cones cannot sense light and this results in vision loss.
What are the current treatments for LCA?
Current treatment of LCA is supportive and includes periodic ophthalmic evaluation for vision assessment and in those patients with residual vision, assessment of the presence of amblyopia, glaucoma or cataract. Treatments under investigation include gene therapy, neuroprotection, and retinal implants. QLT is also evaluating a synthetic retinoid replacement QLT091001 as a potential treatment for LCA.
The retinas in young LCA patients still have relatively normal appearance, even without normal function, both on physical and histological examination. This provides the potential to use a treatment intervention to stop the degeneration before much of the permanent damage takes place and possibly to improve vision.
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