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Gene therapy restores partial vision
by Neka Sehgal - October 25, 2009 - comments
Gene therapy significantly improved the vision of people afflicted with a rare genetic eye disorder
Philadelphia, October 24 -- There is heartening news for those who are virtually blind due to a genetically-inherited sight disorder. Doctors in the U.S. have been successful in restoring some sight in people with a previously incurable eye condition known as Leber’s congenital amaurosis (LCA) by using an experimental form of gene therapy.
LCA is an inherited eye disease which sets on in childhood and usually progresses to total blindness by the age of 30 to 40.
Children born with LCA have defects in a gene called RPE65 that helps the retina's light-sensing cells make rhodopsin, a pigment needed to absorb light. Without rhodopsin, there is a gradual loss of sight due to degeneration of the retina leading to blindness.
Jean Bennett, MD, PhD, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, and colleagues from the Children's Hospital of Philadelphia, assessed the effect of gene therapy on retinal and visual function in people afflicted with the same, rare progressive illness.
The trial was a very small study of 12 people, which included four children and eight adults. To carry out the therapy, doctors injected the healthy-gene carrying virus directly into the retina of the worst eye.
Outcome of the small trial
While the treatment didn't restore normal eyesight in any of the patients, all the participants exhibited an increase in their vision to walk without aid following the procedure.
Also, it was noted that the younger patients reacted better to the therapy and gained more light sensitivity than the adults.
“All 12 patients given gene therapy in one eye showed improvement in retinal function. The effect was stable during follow-up. The results support our hypothesis that the response to subretinal gene therapy depends on the extent of retinal degeneration and, therefore, the age of the patient,” stated Dr. Jean Bennett.
Bennett further stated, "The clinical benefits have persisted for nearly two years since the first subjects were treated with injections of therapeutic genes into their retinas."
Study a breakthrough for retinal diseases
Katherine A. High, M.D., author of the study and the director of the Center for Cellular and Molecular Therapeutics that sponsored the clinical trial at The Children's Hospital of Philadelphia declared, "This result is an exciting one for the entire field of gene therapy.
"This study reports dramatic results in restoring vision to patients who previously had no options for treatment. These findings may expedite development of gene therapy for more common retinal diseases, such as age-related macular degeneration."
The findings are reported in an article published in online edition of The Lancet.