deutan

Deutan is a category of color vision deficiency characterized by impaired perception of greens due to anomalies in the medium-wavelength (M) cone photoreceptors. It is one of the major red-green color vision deficiencies, which also includes protan deficiencies related to the long-wavelength cones.

Forms and definitions: The most common form is deutanomaly (deuteranomaly), where the M-cone sensitivity is shifted, causing greens to appear yellower and leading to confusions between certain greens and reds. A more severe form is deutanopia (deuteranopia), in which M cones are absent or nonfunctional, producing greater difficulty in distinguishing greens from reds and reducing the ability to perceive green hues.

Genetics and prevalence: Deutan defects are typically inherited in an X-linked recessive pattern, so males are more often affected, while females may be carriers or occasionally show mild signs. Prevalence varies by population, but red-green deficiencies are relatively common among people of Northern European descent.

Diagnosis: Screening commonly uses Ishihara color plates to detect red-green deficiencies. More detailed assessment can involve an anomaloscope, which measures precise spectral color matching to classify the defect as deutanomaly or deuteranopia.

Impact and management: There is no cure for inherited deutan defects. Management emphasizes adaptation and accessibility, such as using color cues in combination with patterns or textures, high-contrast designs, and color-blind–friendly palettes to reduce reliance on green discrimination in daily activities and safety-critical tasks.