Scientists have achieved significant progress toward partially restoring sight in patients with severe visual impairment and profound vision loss. According to a new study by the University of Pittsburgh and the Institute of Molecular and Clinical Ophthalmology Basel, optogenetic gene therapy proved safe for patients with retinitis pigmentosa and was associated with improvements in certain visual functions.
Optogenetics is an innovative technology for whose development scientists were awarded the 2026 Nobel Prize in Physiology or Medicine a few days ago, on October 5.
When a disease such as retinitis pigmentosa destroys the eye’s photoreceptor cells, the ability to perceive light is lost. Although this pathology may be linked to more than a hundred different genetic changes, the main advantage of optogenetics is that its effectiveness does not depend on a specific gene mutation. Retinal ganglion cells, which transmit visual information to the brain, are damaged relatively late in the disease, and a portion of them retains functional status. Using an adeno-associated virus (AAV) vector—a carrier of genetic information—researchers deliver instructions to these surviving cells to produce ChrimsonR, a light-sensitive protein that makes the cells sensitive to amber light.
The system works via special goggles: a camera captures an image, a portable processor converts it into pulses of light and projects it onto the retina, activating the retinal ganglion cells modified with the ChrimsonR protein. This allows patients to perceive certain objects, determine their location (for example, find a notebook or a door, or follow a line), and in some cases even touch them. Notably, extended training using the goggles was associated with better outcomes.
This was a small-scale, open-label study involving 10 patients who were monitored for up to five years following treatment. According to the results: 7 out of 10 patients experienced increased sensitivity to light (with the scale of increase ranging from 2- to 62.3-fold); 6 patients showed clinically meaningful improvements that persisted for several years.
Regarding safety, 34 eye-related adverse events were reported in 9 out of 10 participants during the study (23 mild, 10 moderate, and one severe). The only severe event was a temporary occlusion of the central retinal artery, which resolved within a few minutes, while no systemic side effects were recorded.
However, the achievement also has certain limitations. The treated cells are arranged in a ring around the fovea (the area in the macula responsible for high-resolution central vision), which is why detailed perception, including facial recognition, has not yet been restored. In addition, the method requires a functionally preserved optic nerve for the signal to reach the brain.
Scientists consider this achievement a fundamentally important first step toward fully restoring visual function.
