<unk> , a<unk>  vision deficiency in humans, is the inability to perceive differences between some of the<unk> s that other people can distinguish. It is most often of genetic nature, but may also occur because of eye, nerve, or brain damage, or due to exposure to certain chemicals. The English chemist John Dalton in 1798 published the first scientific paper on the subject, "Extraordinary facts relating to the vision of<unk> rs",
after the realization of his own<unk> ; because of Dalton's work, the condition is sometimes called Daltonism, although this term is now used for a type of<unk>  called deuteranopia.<unk>  is usually classed as disability; however, in selected situations<unk>  blind people have an advantage over people with normal<unk>  vision. There are some studies which conclude that<unk>  blind individuals are better at penetrating certain camouflages. Monochromats may have a minor advantage in dark vision, but only in the first five and a half minutes of dark adaptation.
Color blindness
Snow blindness
Myopia
Cortical blindness
Amblyopia
Red eye  
Red eye
Red eye 