Eye Drops Restore Vision in Blind Mice
Light-activated eye drops restored vision in blind mice, offering a potential new treatment for degenerative blindness without gene therapy or implants.
Scientists have created light-activated drugs that helped blind mice perceive light again. The findings, published in the Journal of the American Chemical Society (JACS), were led by the Institute for Bioengineering of Catalonia (IBEC).
Photoreceptor degeneration drives major causes of blindness like age-related macular degeneration (AMD) and retinitis pigmentosa (RP). These disorders affect about 200 million people globally. Existing approaches, such as gene therapy or electronic implants, can be invasive, costly, or suitable only for specific genetic cases.
A New Class of Photoswitchable Drugs
The research consortium developed a new class of photoswitchable small-molecule drugs called prosthe6. These compounds are designed to restore visual function without genetic modification or implanted devices. They can be delivered by injection or even as eye drops.
"These molecules do not cure blindness, because they do not address the cause of photoreceptor degeneration," explained Pau Gorostiza, ICREA Research Professor at IBEC and a study co-leader. "But they are remarkably effective at restoring sight, and they do so using a very simple and potentially patient-friendly approach." The goal was to reactivate retinal processing at the same level as the lost photoreceptor cells, according to co-first author Rosalba Sortino.
Restoring Behavior in Animal Models
The technique relies on photopharmacology, where a drug's activity is reversibly controlled using light. In tests, prosthe6 restored saccadic eye movements in blinded zebrafish larvae.
Crucially, the treatment restored innate light-avoidance behavior in mouse models of AMD and RP. Blind mice, which normally lose the instinct to prefer dark areas, spontaneously favored dark spaces after receiving prosthe6. This occurred at illumination levels similar to indoor or overcast outdoor light, indicating restored functional light perception. No training was needed.
Two compounds, prosthe6-12 and prosthe6-15, produced especially promising results. The restored behaviors appeared after injection and also following topical administration as eye drops.
Molecular Prostheses Target Surviving Circuitry
Prosthe6 works by targeting ON bipolar cells, retinal neurons that normally receive information from photoreceptors. In degenerative diseases, this underlying circuitry often remains intact but inactive. The compounds target a protein (mGlu6) within this circuitry, effectively substituting for some function of the missing photoreceptors.
"This creates a major therapeutic opportunity," explained study co-leader Pedro de la Villa. When light hits the eye, the molecules change shape, triggering signaling that resembles the normal visual process. The researchers describe them as "molecular prostheses." They function under ordinary illumination without needing specialized light sources.
Path Toward Potential Therapies
The findings come after the publication of the first clinical trial of a photopharmacological drug for vision restoration, suggesting the field is moving toward potential clinical use. The prosthe6 technology is patented, and researchers are now studying its safety and formulation to extend the duration of the effect.
The team is working with a spin-off company in formation, Eyelumina, to secure investments for translational development and future clinical trials. "Turning this into a therapy is a long and laborious process," said Gorostiza. He added that the results show a realistic possibility of restoring high-quality vision non-invasively with a mechanism independent of the specific retinal disorder. If successful in people, it could provide a widely accessible alternative for those with advanced retinal degeneration who currently have no effective treatments. The project received early funding from several foundations and government programs.
