An experimental gene treatment improved light sensitivity in seven of ten volunteers with severe retinitis pigmentosa. This inherited disease destroys light-sensitive cells in the retina, the layer at the back of the eye, and can cause permanent blindness. The results were published in The New England Journal of Medicine.
Rather than replacing dead cells, the researchers targeted surviving nerve cells that carry visual information to the brain. Genetic instructions delivered into the eye allow these cells to produce ChrimsonR, a protein that responds to light. Patients also use special glasses with a camera and projector, which process images and send light signals to the retina.
Six participants became at least four times more sensitive to light, meeting the researchers' measure of a clinically meaningful improvement. However, this does not mean that normal vision returned. Patients can detect some visual information that was previously unavailable to them.
The early trial mainly assessed safety rather than proving effectiveness. Nine participants experienced 34 eye-related problems, including one serious event. One patient's central retinal artery, an important blood vessel in the eye, became temporarily blocked after the injection. Blood flow returned within minutes after medicine reduced pressure inside the eye. The researchers consider the results promising, but larger studies are needed to assess both safety and effectiveness.
