Gene therapy for congenital blindness has taken another step forward, as researchers further improved vision in three adult patients previously treated in one eye. After receiving the same treatment in their other eye, the patients became better able to see in dim light, and two were able to navigate obstacles in low-light situations. No adverse effects occurred.

Neither the first treatment nor the readministered treatment triggered an immune reaction that cancelled the benefits of the inserted genes, as has occurred in human trials of gene therapy for other diseases. The current research targeted Leber congenital amaurosis (LCA), a retinal disease that progresses to total blindness by adulthood.  

Scientists from the Perelman School of Medicine at the University of Pennsylvania and The Children’s Hospital of Philadelphia led the study, published today in Science Translational Medicine.

“Patients have told us how their lives have changed since receiving gene therapy,” said study co-leader Jean Bennett, M.D., Ph.D., F.M. Kirby professor of Ophthalmology at Penn. “They are able to walk around at night, go shopping for groceries and recognize people’s faces—all things they couldn’t do before. At the same time, we were able to objectively measure improvements in light sensitivity, side vision and other visual functions.”

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