Volker Busskamp1, Botond Roska2,3 and Jose-Alain Sahel4,5 1Degenerative Retinal Diseases, University Hospital Bonn, 53127 Bonn, Germany 2Institute of Molecular and Clinical Ophthalmology Basel, 4031 Basel, Switzerland 3Department of Ophthalmology, University of Basel, 4001 Basel, Switzerland 4Department of Ophthalmology, UPMC Vision Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA 5Institut Hospitalo-Universitaire FOReSIGHT, Sorbonne Universite, Inserm, Quinze-Vingts Hopital de la Vision, 75012 Paris, France Correspondence: saheljaupmc.edu

Optogenetics has emerged over the past 20 years as a powerful tool to investigate the various circuits underlying numerous functions, especially in neuroscience. The ability to control by light the activity of neurons has enabled the development of therapeutic strategies aimed at restoring some level of vision in blinding retinal conditions. Promising preclinical and initial clinical data support such expectations. Numerous challenges remain to be tackled (e.g., confirmation of safety, cell and circuit specificity, patterns, intensity and mode of stimulation, rehabilitation programs) on the path toward useful vision restoration.