University of Pennsylvania researchers and colleagues have used gene therapy to safely restore vision in three young adults with a rare form of congenital blindness.

The patients have one form of Leber congenital amaurosis (LCA), a group of inherited blinding diseases that damage light receptors in the retina. The diseases usually start in childhood and cause complete blindness by the 20’s or 30’s.

The researchers injected a genetically engineered adeno-associated virus carrying a normal version of the gene RPE65 (mutated in the patients’ form of LCA) into one eye of each patient.

Although the patients didn’t achieve normal eyesight, their vision improved from detecting hand movements to reading lines on an eye chart. The LCA gene therapy vector showed no signs of causing inflammation in the retina or other toxic side effects.

University of Pennsylvania and The Children’s Hospital of Philadelphia News Release