Chemical photoswitch for vision

A photopharmacological route to light sensitivity that needs no gene therapy: small azobenzene-based molecules (e.g. DENAQ, BENAQ) change shape under light and thereby gate endogenous ion channels, transiently making surviving retinal neurons light-responsive after intraocular injection. Some variants preferentially confer sensitivity on degenerated retina.

The appeal is a drug rather than a permanent genetic change, tunable and in principle reversible, but the effect washes out and must be re-dosed, wavelength and intensity requirements are demanding, and cell-type targeting is less precise than opsin delivery. It remains preclinical or early relative to optogenetic and electronic approaches.