There are many types of color blindness. The most common varieties are hereditary (genetic) photoreceptor disorders, but it is also possible to acquire color blindness through damage to the retina, optic nerve, or higher brain areas. Higher brain areas implicated in color processing include the parvocellular pathway of the [[lateral geniculate nucleus]] of the [[thalamus]], and [[visual area V4]] of the [[visual cortex]]. Acquired color blindness is generally unlike the more typical genetic disorders. For example, it is possible to acquire color blindness only in a portion of the visual field but maintain normal color vision elsewhere. Some forms of acquired color blindness are reversible. Transient color blindness also occurs (very rarely) in the [[aura]] of some [[migraine]] sufferers.
[[Image:TestDeuGamma165.png|frame|right|Someone who is deuteranopic might not see this number. Please note that the second digit in this number may be difficult to discern even by those with normal vision.]]
[[Image:TestTriGamma165.png|frame|right|Someone who is tritanopic might not see this number.]]
