What does deuteranomaly mean?
Deuteranomaly is the most common form of red–green colour vision deficiency, affecting roughly five per cent of males though far fewer females, since it is carried on the X chromosome. In someone with deuteranomaly, the retinal cones responsible for sensing green light do not respond normally: their peak sensitivity is shifted toward longer wavelengths, so greens look muted or brownish and subtle differences between green, orange, and red become hard to judge. Unlike deuteranopia, where green-sensitive cones are entirely absent, deuteranomaly leaves all three cone types working — just imperfectly — which makes it an 'anomalous trichromacy' and usually milder. Many affected people discover it only by accident, for example when failing an Ishihara plate test during an eye examination or occupational screening. The word is chiefly clinical, appearing in optometry, genetics, and design-accessibility writing, and it carries no emotional charge; its everyday counterpart is simply 'colour blindness'.
nounA form of red–green colour blindness in which the green-sensitive cones of the retina are abnormally sensitive, causing a mild to moderate deficiency in distinguishing certain shades of green from red. It is the most common type of colour vision deficiency.
- A congenital abnormality of the M-cones (middle-wavelength photopigment) that impairs discrimination between greens and reds, classified as an anomalous trichromacy.
"Because his deuteranomaly was mild, he passed most colour vision tests without difficulty and only struggled with pale pastel shades."
"Screening at the air-force medical revealed a mild deuteranomaly that had gone unnoticed for years."
"Designers increasingly check palettes against deuteranomaly simulations to keep interfaces accessible."
Rarely pluralised in practice because the term usually refers to the condition generally rather than to individual instances.
"Different mutations of the OPN1MW gene produce deuteranomalies of varying severity."
Roughly one man in twenty has some degree of deuteranomaly — yet many never realise it until they fail a routine Ishihara plate test as adults.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of deuteranomaly
The term combines the Greek-derived prefix 'deutero-', meaning 'second', referring to the second of the three cone photopigments (the middle-wavelength, green-sensitive one), with '-anomaly', ultimately from Greek 'anōmalia', meaning irregularity. Related terms such as 'deuteranopia' and 'protanopia' were coined within the same late-nineteenth-century framework of classifying inherited colour-vision defects, alongside 'tritan-' forms affecting blue-yellow perception. Its cognates therefore include other 'deutero-' compounds like 'deuterium' and 'deuteragonist', as well as 'anomaly' itself.
Related word forms
How deuteranomaly is actually used
A clinical/technical term used mainly in ophthalmology, optometry, genetics, and accessibility contexts; in everyday speech people more often say 'colour blindness' or 'being colour-blind'. The adjective form 'deuteranomalous' describes affected individuals or vision. Severity varies widely, so some people with deuteranomaly function almost normally while others struggle noticeably with red–green distinctions.
Easily confused with deuteranomaly
Deuteranopia is a complete absence of functioning green-sensitive cones producing more severe colour vision loss, whereas deuteranomaly is an abnormal (shifted) sensitivity in those same cones, resulting in a milder deficiency.
Protanomaly affects the red-sensitive cones rather than the green-sensitive ones; both produce red-green confusion but through different cone abnormalities.