Editing Color blindness (section)

====Monochromacy====
{{Main|Monochromacy}}
Monochromacy is often called ''total color blindness'' since there is no ability to see color. Although the term may refer to acquired disorders such as [[cerebral achromatopsia]], it typically refers to congenital color vision disorders, namely [[Achromatopsia|rod monochromacy]] and [[blue cone monochromacy]]).<ref name=":0">{{cite web|url=http://www.colourblindawareness.org/colour-blindness/types-of-colour-blindness/|title=Types of Colour Blindness|work=Colour Blind Awareness|url-status=live|archive-url=https://web.archive.org/web/20140529052207/http://www.colourblindawareness.org/colour-blindness/types-of-colour-blindness/|archive-date=2014-05-29}}</ref><ref name=blom>
{{cite book |title       = A Dictionary of Hallucinations |first       = Jan Dirk |last        = Blom |publisher   = Springer |year        = 2009 |isbn        = 978-1-4419-1222-0 |page        = 4 |url=https://books.google.com/books?id=KJtQptBcZloC&pg=PA4 |url-status     = live |archive-url  = https://web.archive.org/web/20161227164302/https://books.google.com/books?id=KJtQptBcZloC&pg=PA4 |archive-date = 2016-12-27 }}</ref>

In cerebral achromatopsia, a person cannot perceive colors even though the eyes are capable of distinguishing them. Some sources do not consider these to be true color blindness, because the failure is of perception, not of vision. They are forms of [[visual agnosia]].<ref name=blom/>

[[Monochromacy]] is the condition of possessing only a single channel for conveying information about color. Monochromats are unable to distinguish any colors and perceive only variations in brightness. Congenital monochromacy occurs in two primary forms:
# Rod monochromacy, frequently called complete [[achromatopsia]], where the retina contains no cone cells, so that in addition to the absence of color discrimination, vision in lights of normal intensity is difficult.
# Cone monochromacy is the condition of having only a single class of cone. A cone monochromat can have good pattern vision at normal daylight levels, but will not be able to distinguish hues. Cone monochromacy is divided into classes defined by the single remaining cone class. However, red and green cone monochromats have not been definitively described in the literature. [[Blue cone monochromacy]] is caused by lack of functionality of L (red) and M (green) cones, and is therefore mediated by the same genes as red–green color blindness (on the X chromosome). Peak spectral sensitivities are in the blue region of the visible spectrum (near 440&nbsp;nm). People with this condition generally show [[nystagmus]] ("jiggling eyes"), [[photophobia]] (light sensitivity), reduced [[visual acuity]], and [[myopia]] (nearsightedness).<ref>{{cite journal | vauthors = Weiss AH, Biersdorf WR | title = Blue cone monochromatism | journal = Journal of Pediatric Ophthalmology and Strabismus | volume = 26 | issue = 5 | pages = 218–23 | year = 1989 | doi = 10.3928/0191-3913-19890901-04 | pmid = 2795409 | s2cid = 23037026 }}</ref> Visual acuity usually falls to the 20/50 to 20/400 range.