Most individuals with color vision deficiency have had it since birth. However, people can develop it later in life. If it develops due to a health problem, color blindness can worsen over time.
Color vision deficiency means an individual cannot perceive color the same way as those without the condition. Most often, people find it difficult to distinguish between two different colors, such as reds and greens or blues and yellows.
This may only apply in low light for people with mild color vision deficiency, but those with more advanced symptoms may not be able to distinguish colors in any light. Color vision deficiency develops due to problems with the cone receptors at the back of the eye that detect the different frequencies of various colors.
People usually have color vision deficiency from birth. They often inherit color vision deficiency in their genes, usually from a female parent. This is because some types of color vision deficiency, such as red-green color blindness are X-linked. This means they inherit the gene alteration causing color blindness from the X chromosome.
However, various health problems can damage either the cone receptors or the part of the brain that interprets color, meaning color vision deficiency may develop later on. Doctors refer to this as acquired color vision deficiency.
People are far more likely to inherit color vision deficiency than acquire it through disease or injury. In fact, color vision deficiency is one of the most common inherited conditions. Common gene alterations that can lead to color vision deficiency occur in the following genes:
- OPN1LW
- OPN1MW
- OPN1SW
The severity of color blindness does not change for people with inherited color vision deficiency. However, those with acquired color blindness may find that symptoms can quickly change from mild and stable to severe and progressive, depending on the cause.
Most people with acquired color vision deficiency do not completely lose the ability to process colors. As the condition progresses, they may begin to develop vision that resembles anomalous trichromacy. This means that although all three types of cones are functioning, one type is not working correctly.
Some people with more severe acquired color vision deficiency develop monochromacy.
The type of color vision deficiency a person has depends on which types of cones are missing or not functioning.
Red-green color vision deficiency
This is the most common type in both inherited and acquired forms. Red-green color vision deficiency makes distinguishing reds and greens difficult in various ways, including:
- deuteranomaly, in which some shades of green appear red
- protanomaly, in which certain shades of red appear duller and greener
- protanopia and deuteranopia, in which a person cannot distinguish red and green at all
Blue-yellow color vision deficiency
This is less common than red-green color vision deficiency. It makes distinguishing several colors difficult. The two main forms are tritanomaly and tritanopia.
People with tritanomaly find it hard to separate blue and green or yellow and red. Those with tritanopia see duller colors and also cannot distinguish between blue and green, red and purple, or yellow and pink.
Complete color vision deficiency
Some people have monochromacy or achromatopsia, meaning they cannot see color at all and perceive only grays. They may also be highly sensitive to light. This type is rare and only inherited. It usually only presents from a young age, meaning it does not develop later in life.
Acquired color vision deficiency can occur as a result of damage to the eye or the area of the brain that interprets color. The
- eye diseases, such as age-related macular degeneration (AMD), retinitis pigmentosa, or glaucoma
- nervous system and brain diseases, including multiple sclerosis (MS), some strokes, and Alzheimer’s disease
- other chronic diseases, such as type 2 diabetes, liver disease, chronic alcohol use disorder, and sickle cell anemia
- injuries, such as those from trauma or tumors
- aging, as being over 70 years of age can lead to declining color vision
- exposure to industrial toxins, including carbon monoxide, carbon disulfide, and lead
- medication side effects, including some antibiotics, barbiturates, drugs to treat tuberculosis, medications for high blood pressure, and those to manage some nervous system disorders
Color vision deficiency mainly causes
- problems when distinguishing between different colors
- difficulties in perceiving the brightness of colors
- separating different shades of the same color
These symptoms are often mild and do not impair daily function. People often adjust to minor differences in color perception. Those with severe color vision deficiency might notice other symptoms, including the eyes moving rapidly from side to side or an increased sensitivity to light.
Outside of the most severe form, color vision deficiency does not affect a person’s visual clarity.
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However, if an underlying health problem causes color vision deficiency later in life, addressing the underlying problem, where possible, can help reduce symptoms. For example, if a medication causes color vision deficiency, a doctor may change the prescription to a different option or adjust the dosage.
If color vision deficiency is severe or impacts daily life, people can wear glasses or contacts that increase the contrast between colors to help individuals tell them apart. Certain apps can also provide visual aids that allow people to take photos and identify colors through different means.
Inherited color vision deficiency is more common than the acquired type that can develop later in life. However, people can acquire color vision deficiency later in life due to injury, illness, medication side effects, aging, or exposure to toxins in their environment.
The symptoms of acquired color vision deficiency can change over time and might get worse or better. However, treating the underlying condition may resolve acquired color vision deficiency.