Color blindness as part of the retinal damage caused by diabetes. Vitamin A deficiency may also cause color blindness. Some subtle forms of color blindness may be associated with chronic solvent-induced encephalopathy (CSE), caused by long-time exposure to solvent vapors. Red–green color blindness can be caused by ethambutol, a drug used in the treatment of tuberculosis. The typical human retina contains two kinds of light cells: the rod cells (active in low light) and the cone cells (active in normal daylight). Normally, there are three kinds of cone cells, each containing a different pigment, which are activated when the pigments absorb light.
Light effects on circadian rhythm tract (RHT) the suprachiasmatic nucleus (SCN) of the hypothalamus receives light information from these ipRCGs. The ipRGCs serve a different function than rods and cones, even when isolated from the other components of the retina, ipRGCs maintain their photo-sensitivity and as a result can be sensitive to different ranges of the light spectrum. Additionally, ipRGC firing patterns may respond to light conditions as low as 1 lux whereas previous research indicated 2500 lux was required to suppress melatonin production. Circadian and other behavioral responses have shown to be more sensitive at lower wavelengths than the photopic luminous efficiency function which