Light effects on circadian rhythm collected by rod cells and cone cells and the retinal ganglion cells (RGCs), or it is directly collected by these RGCs. The RGCs use the photopigment melanopsin to absorb the light energy. Specifically, this class of RGCs being discussed is referred to as "intrinsically photosensitive," which just means they are sensitive to light. There are five known types of intrinsically photosensitive retinal ganglion cells (ipRGCs): M1, M2, M3, M4, and M5. Each of these differently ipRGC types have different melanopsin content and photosensitivity. These connect to amacrine cells in the inner plexiform layer of the retina. Ultimately, via this retinohypothalamic
Laser safety retina at near-infrared wavelengths and to more frontal parts of the eye at longer wavelengths. The table below summarizes the various medical conditions caused by lasers at different wavelengths, not including injuries due to pulsed lasers. The skin is usually much less sensitive to laser light than the eye, but excessive exposure to ultraviolet light from any source (laser or non-laser) can cause short- and long-term effects similar to sunburn, while visible and infrared wavelengths are mainly harmful due to thermal damage. FAA researchers compiled a database of more than 400 reported incidents occurring between 1990 and 2004 in which