In many of these conditions, photoreceptor cells—the retina’s light detectors—progressively degenerate and die. Although the downstream retinal neuronal circuitry remains largely intact and functionally viable, it no longer receives the light signals needed to drive visual processing toward the brain. This opportunity has fueled intense research efforts to develop treatments capable of restoring light sensitivity to the eye.

Current strategies include gene therapy—effective only for a very small subset of patients with specific mutations—and electronic retinal prostheses, which are invasive, expensive and require extensive training for effective use. More recently, optogenetics and light-responsive drugs have entered clinical testing, with the latter showing encouraging safety results, but achieving high-quality vision at ambient illumination levels remains a major challenge.