New research from the Perelman School of Medicine at the University of Pennsylvania and The Children’s Hospital of Philadelphia (CHOP) suggests gene therapy that often leads to sight restoration also strengthens the brain’s visual pathways. 

Study participants received the gene therapy in their worse-seeing eye, and the investigators saw a significant difference between the side of the brain connected to the treated eye and the side connected to the untreated eye, even though they imaged the brains only two years later.   

They studied 10 patients diagnosed with Leber’s congenital amaurosis Type 2 (LCA2), a rare disease that causes the retina to degenerate slowly. Patients typically have limited visual function at birth, experience progressive loss of vision and are often completely blind by mid-life. 

Study participants commonly went from being blind or near blind to being partially sighted and able to navigate almost normally. Researchers then sought to better understand how, or even if, the pathways in the brain recovered. Using advanced MRI, they discovered that the untreated eyes had weaker connectivity with the brain than the treated eyes, suggesting gene therapy was helping to improve that connection. 

“That was what we expected to see—the more the treated eye sees the world and interacts with the environment, the more it stimulates the pathway and the stronger the connecting pathway becomes between the retina and the brain,” said lead author Manzar Ashtari, PhD, a director at the Center for Advanced Retinal and Ocular Therapeutics in the Department of Ophthalmology at Penn. 

Dr. Ashtari and colleagues are continuing their research through a larger Phase III clinical trial and hope the FDA will review the results next year.

Ashtari M, Zhang H, Cook PA, et al. Plasticity of the human visual system after retinal gene therapy in patients with Leber’s congenital amaurosis. Science Translational Medicine. 2015;7(296):296ra110.