The most common types of color blindness, or color vision deficiency, are genetic. However, other types may develop due to injuries, eye diseases, health problems, and side effects of treatment.
People with color vision deficiency see colors differently. They may experience difficulties seeing the differences between certain colors, the brightness of some colors, or different shades of the same color.
The retina at the back of the eye is a layer of cells that detect light. Some of these cells, called cone and rod receptors, help the brain perceive and process color. Three sets of cone and rod receptors are more sensitive to reds, greens, and blues. The different types of cones contain variations of a pigment, known as opsin, to detect colors in a certain frequency range.
Seeing certain colors might be difficult if one or more sets of cones do not function correctly. This article explains the link between color vision deficiency and a person’s genes.
For most people with color blindness, genetics are the cause. Three genes in particular help the body regulate opsin production:
- OPN1LW
- OPN1MW
- OPN1SW
Changes to these genes may affect how the brain processes color. According to the advocacy group Colour Blind Awareness (CBA), color vision deficiency is one of the most common inherited conditions.
The type of color blindness may depend on which gene variation a person inherits. The following table shows which genes relate to which type of color deficiency.
| Type of color vision deficiency | Affected gene or genes |
|---|---|
| red-green | OPN1LW or OPN1MW |
| blue-yellow | OPN1SW |
| blue-cone monochromacy | OPN1LW or OPN1MW |
People with red-green color vision deficiency might find it difficult to see
Blue-cone monochromacy means that someone can only see shades of gray and cannot perceive colors at all.
According to CBA, around 1 in 12 males and 1 in 200 females have color vision deficiency. Different types of color vision deficiency have different ways of passing from one generation to the next, known as inheritance patterns.
The genes that play a role in red-green color vision deficiency and blue cone monochromacy link to the X chromosome, one of two chromosomes that define biological sex. Typically, these genes relate to the chromosome that a person assigned female at birth (AFAB) passes on. This means these types have an X-linked recessive inheritance pattern.
Those assigned male at birth usually have one X chromosome, so only a single genetic change may be necessary to have red-green color vision deficiency. Generally, those AFABs can only develop these types if they inherit a gene alteration from both biological parents. As such, red-green color vision deficiency is more common in males.
Blue-yellow color vision deficiency has an autosomal dominant pattern. This type can develop if only one copy of the altered OPN1SW gene is present. People often acquire this from a parent who also has blue-yellow color vision deficiency. As such, the probability of inheriting it if one parent also has the condition is 50%.
The most common cause of color vision deficiency is genetics, but it can also develop due to damage in the brain region that supports color processing. This can occur for
- eye disease, including age-related macular degeneration and glaucoma
- brain and nervous system diseases, such as multiple sclerosis (MS) or Alzheimer’s disease
- medication side effects, including a rheumatoid arthritis medication called hydroxychloroquine
- brain or eye injuries, such as retinal detachment
- some tumors
If a person acquires color vision deficiency through disease or injury, it may affect both eyes differently. Disease-triggered color vision deficiency usually worsens over time.
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As such, gene therapy is currently unable to treat color blindness. However, research is ongoing, and with further tests and trials, it may be an option in the future.
Several types of color vision deficiency have genetic causes. The most common type is red-green color vision deficiency, and the gene affecting this has links to the X chromosome. Other types relate to different genes and have different inheritance patterns.
People can also acquire color vision deficiency due to injury, illness, or side effects from treatment. Currently, no gene therapy treatment is available to alter specific genes and repair color vision deficiency.