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Vision Improves with Gene Therapy for Congenital Eye Disease

Researchers at the University of Pennsylvania report success in restoring vision to three patients with LCA, or Leber congenital amaurosis, a group of inherited diseases that destroy light receptors in the retina. Affected individuals develop symptoms in childhood and progress to total blindness by the time they are in their twenties or thirties. Gene therapy improved eyesight in the three patients, ages 19, 26 and 26, taking part in the study.

The researchers employed a vector to replace the mutated RPE65 gene, which causes one form of LCA. The vector was an adeno-associated virus genetically engineered to carry a normal version of RPE65 gene.

The three study participants received vector injections in one eye between October 2007 and January 2008. The injected eye in each patient was the one with the poorest vision. Although none of the patients achieved normal eyesight, all study participants reported improvement that included reading lines on an eye chart where before only hand movements could be detected.

Light sensitivity improved as well by as much as three times and the injected eye eventually improved in function to surpass the uninjected eye, which previously had been the better of the two.

After injections, patients also experienced reduced nystagmus, which is an involuntary movement of the eyes commonly occurring in LCA. It is thought that the reduced nystagmus helped improve vision in both eyes.

The research team, working from The Children’s Hospital of Philadelphia, reported no signs of inflammation or toxic side effects associated with the injections.

The team included researchers from the University of Pennsylvania, The Children’s Hospital of Philadelphia, and several other institutions in the United States and two from Italy, the Telethon Institute of Genetics and Medicine and the Second University of Naples.

The findings of this clinical trial can be found online at the New England Journal of Medicine’s website.

1. Leber congenital amaurosis is an autosomal recessive disorder, meaning that both parents must be carriers of the mutated gene. When this happens, their children have a 25% chance of developing the disease.
2. At this time, scientists are unable to determine who is a carrier for the mutated gene.

Source: Foundation Fighting Blindness

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