Summary
This review highlights that the inner retina contains multiple non-visual opsins (melanopsin, encephalopsin, neuropsin) expressed in retinal ganglion cells, horizontal cells, and glial cells, which respond preferentially to blue and near-violet light and regulate circadian rhythms, pupillary responses, and other subconscious functions. For lighting designers, this underscores the importance of short-wavelength (blue/violet) light content in driving non-visual biological effects beyond simple brightness perception.
Key Findings
- Melanopsin (Opn4), encephalopsin (Opn3), and neuropsin (Opn5) are expressed in non-visual inner retinal cells including ipRGCs, horizontal cells, and MĂĽller glial cells of vertebrates.
- These non-visual photopigments preferentially respond to blue and near-violet wavelengths of light, extending the spectrum of physiologically relevant light stimulation beyond classical rod and cone photoreceptors.
- Melanopsin-expressing ipRGCs are established mediators of circadian clock entrainment and the pupillary light reflex, and may also modulate lateral interactions between visual photoreceptors and horizontal cells.
- Non-visual photoreceptor expression occurs from early developmental stages, even before functional vision is established.
Categories
The Science of Light: Reviews the biology of melanopsin (Opn4), encephalopsin (Opn3), and neuropsin (Opn5) in non-visual photoreceptors including ipRGCs, horizontal cells, and MĂĽller glial cells, and their roles in circadian entrainment and pupillary light reflex.
Eye Health & Vision: Discusses the functional roles of inner retinal photoreceptors beyond image-forming vision, with implications for understanding retinal photobiology and non-visual light responses.
Author(s)
M Guido
Publication Year
2020
Related Publications
The Science of Light
- Phototransduction by retinal ganglion cells that set the circadian clock
- Color appearance models
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Melanopsin is required for non-image-forming photic responses in blind mice
Eye Health & Vision
- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
- Genetic reactivation of cone photoreceptors restores visual responses in retinitis pigmentosa
- Melanopsin and rod–cone photoreceptors play different roles in mediating pupillary light responses during exposure to continuous light in humans
- Characteristic patterns of dendritic remodeling in early-stage glaucoma: evidence from genetically identified retinal ganglion cell types
- Intrinsically photosensitive melanopsin retinal ganglion cell contributions to the pupillary light reflex and circadian rhythm