Color blindness is a term that is commonly used to refer to color vision deficiency, a condition where the ability to see colors clearly, is reduced. Actual color blindness, however, is a rare condition referring to an inability to see any color at all.
As well as having difficulty perceiving colors, individuals with color vision deficiency may also find it difficult to distinguish between them. Poor lighting, in particular, can make it difficult to identify pale or dark colors. The symptoms of color vision deficiency vary in severity, with some people unaware that they even have the condition until it is identified during a vision test. Other people may notice that they perceive slightly different tones or hues of colors to those that others perceive. In rare cases, an individual may perceive multiple colors as only one color.
Types of color vision deficiency
There are two main types of color vision deficiency and these include:
Red–green deficiency – Patients are unable to identify certain shades of red or green. This form of the condition is the most commonly inherited type.
Blue–yellow deficiency – This is a more rare form of color deficiency where it is difficult for a person to differentiate between blue and green. Yellow may be perceived as grey or purple.
In most cases of color vision deficiency, the condition is inherited. However, some illnesses and medication side effects can cause the condition. Color vision deficiencies arise due to an abnormality in the retina where one or more of the three types of cone cell responsible for color perception are dysfunctional or missing.
Diagnosis and treatment
In most individuals, mild color vision deficiency goes unnoticed until the person takes a color vision test. In more severe cases, a person may have difficulty reading maps and interpreting traffic signals or pictures in books or on the internet.
At present, there is no cure for color vision deficiency as the abnormal cone cells in the retina cannot be fixed or replaced. However, the condition often does not have any significant adverse effects on health or prevent a person from living a normal life. People who do find they are affected by their condition in some way often learn ways of adapting that help them cope with the problems their condition can cause. If they have trouble distinguishing the colors of traffic lights for example, they may rely on their knowledge of the lights’ positioning instead.
Reviewed by Sally Robertson, BSc