By Dave Porter

(AXcess News) Reno - Researchers have found that human gene therapy can help some forms of rare blindness in people with very encouraging results that may offer hope to many who suffer from blindness.

The findings were published in the latest edition of the Proceedings of the National Academy of Science (PNAS).

Leber congenital amaurosis, a rare form of inherited blindness, usually causes people with the condition to experience further deteriorations in vision as they grow older.  But patients who received gene therapy in two recent trials experienced improvements in light sensitivity and vision, paving the way for hope in curing the rare condition.

"The treatment involves the injection of healthy copies of one gene, known as RPE65, into the cells of the retina in an effort to get dysfunctional cells to work better. Researchers did this by using specially engineered viruses, or vectors, to deliver the genes," noted Salynn Boyles in a WebMD story on the gene therapy.

Patients in the two trials were measured for vision up to three months after receiving the gene therapy.  "All three patients showed a significant increase in visual sensitivity at 30 days after treatment," the PNAS Abstract notes.  Researchers were delighted to say that "there was no changes in effect up to 90 days later."

The Abstract notes that, "To assess what fraction of full vision potential was restored by gene therapy, we related the degree of light sensitivity to the level of remaining photoreceptors within the treatment area. We found that the intervention could overcome nearly all of the loss of light sensitivity resulting from the biochemical blockade."

But researchers cautioned that, ""However, this reconstituted retinoid cycle was not completely normal. Resensitization kinetics of the newly treated rods were remarkably slow and required 8 h or more for the attainment of full sensitivity, compared with <1 h in normal eyes. Cone-sensitivity recovery time was rapid. These results demonstrate dramatic, albeit imperfect, recovery of rod- and cone-photoreceptor-based vision after RPE65 gene therapy."