What does opsin mean?
An opsin is a light-sensitive protein found in the photoreceptor cells of the retina and in certain other light-sensing tissues. Opsin does not detect light on its own: it binds a molecule derived from vitamin A, called retinal, to form a complete visual pigment. When retinal changes shape in response to light, the associated opsin initiates a biochemical signalling process that helps the nervous system interpret visual information. Different opsins are sensitive to different wavelengths of light, helping explain colour vision and the adaptations of nocturnal or deep-sea animals. In genetics and vision research, the word commonly appears in terms such as “opsin gene,” “opsin protein,” and “rhodopsin opsin.” Although usually discussed in connection with vision, opsins also occur in photoreceptors outside the eyes, including those involved in regulating circadian rhythms.
nounA light-sensitive protein that forms part of visual pigments in the retina. Opsins combine with a form of vitamin A called retinal to enable photoreceptors to detect light.
- A light-sensitive protein that combines with retinal to form a visual pigment used by photoreceptor cells.
"Changes in opsin expression can alter how an animal responds to different wavelengths of light."
"The researchers measured the expression of opsin genes in the fish's retina."
"Mutations in the opsin sequence can produce differences in colour vision."
The plural is used in biological and genetic descriptions of distinct light-sensitive proteins.
"Researchers compared the sequence of opsins in several species of fish."
Your eyes do not detect light with pigment alone: the pigment rhodopsin is a partnership between an opsin protein and retinal, a molecule derived from vitamin A.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does opsin come from?
The name opsin combines Greek opsis, meaning “sight” or “appearance,” with the biochemical suffix -in. Its modern sense developed with the study of retinal pigments and the proteins that combine with retinal to form them. The underlying Greek root also appears in related English words such as optic, optical, and optometry.
How opsin is actually used
This is a specialised term in biology, ophthalmology, and vision science. It refers to the protein component of a visual pigment, not to the complete pigment or to the light-detecting cell itself.