For ten blind patients whose retinas had lost the cells that normally detect light, the treatment began with one injection in the eye with poorer sight. Retinitis pigmentosa had progressively destroyed their photoreceptors, leaving the patients blind.
The injection carried genetic instructions for ChrimsonR, a protein that responds to amber light. Researchers aimed to make surviving retinal ganglion cells light-sensitive, rather than replace the photoreceptors lost to the disease.
Each patient then used special goggles, which turn changes in the visual scene into pulses of amber light. Those pulses activate ChrimsonR in the treated retina.
On 7 October 2026, an international team led by José-Alain Sahel, an ophthalmologist at the University of Pittsburgh and co-founder of GenSight Biologics, and Botond Roska of the Institute of Molecular and Clinical Ophthalmology Basel, reported results from the first clinical cohort of blind people to receive this optogenetic treatment for advanced retinitis pigmentosa.
Retinitis pigmentosa is inherited, and mutations in more than 100 different genes can cause it. In the condition, the retina's photoreceptors gradually lose their ability to respond to light.
Safety was the trial's main measure. Within the limits of the study, the treatment was considered safe, and most eye-related adverse events were mild or moderate.
One severe event occurred immediately after an injection. It resolved within minutes after treatment.
Seven of ten patients became more sensitive to light, while six met the predefined level for a clinically meaningful improvement.
Four of eight patients who completed visual behavioural testing improved at tasks including detecting or locating objects. More patients improved at finding a doorway or following a line while using the goggles.
Patients who spent longer learning to use the goggles tended to do better in object-detection tests, pointing to the role of training and adaptation in the approach.
The work depends on optogenetics, which uses light and a borrowed gene to control the electrical activity of nerve cells. The light-sensitive proteins used in the field were first found in single-celled green algae.
Two days before the results were reported, the Nobel Prize in Physiology or Medicine was awarded on 5 October 2026 to Karl Deisseroth, Peter Hegemann and Georg Nagel for discoveries concerning light-gated ion channels and optogenetics.
Sahel and Roska shared the 2024 Wolf Prize in Medicine for work on restoring vision in blind patients.
As of October 2026, no optogenetic treatment had approval from the US Food and Drug Administration.
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