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Red-Green Deficiency: Causes, Symptoms and Diagnosis

Red-green deficiency is a common visual impairment in which affected individuals have difficulty distinguishing between red and green hues. It is usually inherited and affects men more often than women.

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Things worth knowing about "Red-green deficiency"

Red-green deficiency is a common visual impairment in which affected individuals have difficulty distinguishing between red and green hues. It is usually inherited and affects men more often than women.

What Is Red-Green Deficiency?

Red-green color deficiency (also called red-green color vision deficiency) is a form of color vision impairment in which the ability to distinguish between red and green tones is reduced. It is one of the most common inherited visual impairments worldwide and does not typically affect overall visual acuity.

There are two main subtypes:

Protanomaly (red weakness): The red cones in the retina are altered, leading to reduced sensitivity to red light.
Deuteranomaly (green weakness): The green cones are altered, impairing the perception of green tones.

In more severe cases, the condition is referred to as protanopia (complete red blindness) or deuteranopia (complete green blindness).

Causes

Red-green color deficiency is most commonly congenital (present from birth) and follows an X-linked recessive inheritance pattern. This means the genetic variant is located on the X chromosome. Since males have only one X chromosome, a single altered gene is sufficient to cause the condition. Females, having two X chromosomes, are more often carriers without being affected themselves.

Genetic cause: Mutations in the OPN1LW (red) and OPN1MW (green) cone photopigment genes on the X chromosome.
Acquired cause (rare): Certain eye diseases (e.g., glaucoma, retinal disorders) or toxic exposures can also impair color perception.

Prevalence

Approximately 8% of men and around 0.5% of women in Europe are affected by some form of red-green color deficiency, making it one of the most common genetically determined sensory impairments.

Symptoms

Affected individuals perceive colors differently from people with normal color vision. Typical signs include:

Difficulty distinguishing between red and green tones
Confusion of orange, yellow, brown, and green
Problems reading color-coded diagrams, maps, or traffic signals in certain lighting conditions
The condition is often first noticed in childhood through standardized tests or everyday situations

Red-green deficiency does not cause pain and generally does not reduce overall sharpness of vision.

Diagnosis

Diagnosis is typically made through simple color vision tests performed by an ophthalmologist or optician:

Ishihara plates: The most widely used test, featuring colored dot patterns that conceal numbers or shapes visible only to those with normal color vision.
Farnsworth Panel D-15 test: Colored chips are arranged in order of hue similarity.
Anomaloscope: A specialized optical instrument that produces mixed colors to precisely determine the type and severity of color vision deficiency.

Treatment and Assistive Tools

There is currently no cure for inherited red-green color deficiency. However, several aids can improve daily life:

Color filter lenses and glasses (e.g., EnChroma lenses): These filter specific wavelengths to enhance color contrast, though they do not restore normal color vision.
Apps and software: Smartphone applications can identify colors or adjust images to improve color differentiation.
Accessible design: High-contrast design and additional symbols in everyday environments (e.g., traffic signals with shape indicators) help those affected navigate more easily.

For acquired color vision deficiency, treatment of the underlying condition may partially restore color perception.

Impact on Daily Life and Career

Red-green deficiency can be relevant in certain professions such as aviation, railway operations, or electronics engineering, where normal color vision may be required. In everyday life, however, most individuals learn to compensate effectively once they are aware of their condition.

References

Gegenfurtner, K. R. & Sharpe, L. T. (Eds.) - Color Vision: From Genes to Perception. Cambridge University Press, 1999.
Sharpe, L. T. et al. - Opsin genes, cone photopigments, color vision and color blindness. In: Color Vision: From Genes to Perception, Cambridge University Press, 1999.
World Health Organization (WHO) - International Classification of Diseases (ICD-11): Visual impairment and color deficiency. Available at: www.who.int

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