Leber's congenital amaurosis (LCA) is an inherited degenerative disorder affecting the retina, a light sensitive tissue at the back of the eye which detects light and color. People who suffer from this disease usually have severe visual impairment right from childhood, may be even starting at infancy. Children affected with LCA usually lack night vision and some may even lose daylight vision.
The clinical manifestations include reduced electroretinograms and pupillary light reflexes, nystagmus (rhythmic, involuntary eye fixation instability) as well as fundus abnormalities on ophthalmoscopy.
AdvertisementIt is estimated that about 10% of patients affected with LCA have a mutated form of the gene retinal pigment epithelium-specific 65 kDa (RPE65), which is a protein critical for vision. The RPE65 protein produces a specific form of vitamin A that enables the light-sensitive photoreceptor cells to function. Mutations in the RPE65 gene thus halts the visual cycle and blocks vision.
RPE65 gene replacement therapy was considered as a therapeutic strategy in patients with LCA. A study was conducted on 15 people suffering from LCA, who received a retinal injection of a virus that was designed to produce healthy RPE65. The results of the study were published in the New England Journal of Medicine.
After few days of treatment, some patients demonstrated a remarkable increase in their ability to see dim light, which they had never seen before.
Samuel G. Jacobson, the lead scientist from the University of Pennsylvania's Scheie Eye Institute, Philadelphia, commented, "Gene therapy for LCA demonstrated, we could improve vision in previously untreatable and incurable retinal conditions."
Four out of the fifteen patients reportedly started relying on the area of the retina where the gene therapy injection was given to see lettershus extending their visual life.
These results are quite significant because they represent one of the important steps towards the clinical use of gene therapy for an inherited form of blindness.
Jacobson further added, "We've been able to positively alter and extend the visual life of patients with LCA, and we now have to develop workable strategies for extending it even further."
The study findings suggest that it may be possible to achieve substantial restoration of vision in patients with LCA as long as gene replacement was performed at an early stage in the disease.