An experimental approach is offering a new way to create visual perception for people with advanced retinitis pigmentosa. Instead of repairing the retina's damaged photoreceptors, researchers made surviving retinal cells responsive to light.
In a phase 1/2 clinical trial involving 10 participants, seven showed improved light sensitivity while using specialized goggles. Six had improvements considered clinically meaningful. The treatment did not restore normal sight, but some participants gained limited ability to detect objects and interpret their surroundings.
Rerouting visual signals
Retinitis pigmentosa is a group of inherited conditions that gradually damage photoreceptors, the cells that normally detect light. The disease can arise from mutations in many different genes, and replacing photoreceptors that have already been lost remains a challenge.
The research team, led by scientists from the University of Pittsburgh and the Institute of Molecular and Clinical Ophthalmology Basel, took a different route. They used optogenetics to give surviving retinal ganglion cells--nerve cells that carry visual signals toward the brain--the ability to respond to light.
Researchers delivered genetic instructions for the light-sensitive protein ChrimsonR into one eye of each participant using a modified, non-disease-causing virus. Participants also wore goggles with a camera and light projector. The device processed the scene and projected patterns of light onto the treated retina, activating the modified cells.
A promising early-stage result
Light sensitivity gains varied among participants, ranging from about twice their previous level to more than 60 times. The trial reported no safety concerns among the 10 participants. Its main aim was to evaluate safety, while also assessing whether the approach could support practical visual tasks.
The findings, published in the New England Journal of Medicine, suggest that visual information may still reach the brain through an alternative pathway when the eye's natural light-sensing cells have been severely damaged. Further research will be needed to establish how reliably and broadly the approach can help patients.
If future studies confirm these results, optogenetics could expand the possibilities for restoring useful visual perception when conventional light-sensing cells are no longer available.
