Deuteranomaly

Deuteranomaly is a common inherited color vision deficiency characterized by an altered sensitivity of the medium-wavelength (green) cone photopigment in the retina. In affected individuals, the spectral tuning of the M-cones overlaps more with that of the L-cones, reducing the ability to distinguish greens from reds. This form of red-green color blindness is typically mild to moderate and often goes unnoticed in everyday life.

It is generally caused by genetic variants in the M-cone opsin gene located on the X chromosome and is inherited in an X-linked recessive pattern. As a result, men are more frequently affected, whereas women are usually carriers who may occasionally show mild symptoms.

Prevalence estimates vary by population, but deuteranomaly is the most common color vision deficiency, affecting about 5% of men in many populations of Northern European ancestry, with lower rates in women. Diagnosis relies on standardized color vision tests such as Ishihara plates; for quantification, anomaloscope testing can determine the degree of red-green color misclassification.

Although there is no cure, people with deuteranomaly can adapt through non-color cues and labeling practices. Some color-correcting lenses are marketed to enhance discrimination for certain tasks, but their effectiveness is variable and they do not restore normal color vision.