Colour vision deficiency (colour blindness) is a condition which causes you to see colours differently than most people. This means that if you are colour blind, you may have trouble seeing:1
- The difference between colours, e.g. red and green
- The brightness of colours
- The different shades of colours
Colour vision deficiency affects around 1 in 12 people assigned male at birth (AMAB) (8%) and 1 in 200 people assigned female at birth (AFAB). There are 3 million people with colour blindness in the UK and 300 million people worldwide. Most people with colour blindness adapt to living with it but there are some options available to manage it. Some of the options are special glasses and contact lenses.1
There are different types of colour vision deficiency with rare cases where people are unable to see colour at all (monochromacy). However, most people with colour vision deficiency do not fully see red, green, or light blue. The most common types of colour vision deficiency are red-green colour blindness and blue-yellow colour blindness.
Red-green colour blindness
This is the most common type of colour blindness which makes it difficult to tell the difference between red and green. The four different types of red-green colour blindness are:
- Deuteranomaly - the most common type of red-green colour blindness that makes green look red. It is usually mild and does not severely affect people
- Protanomaly - makes red look less bright and more green
- Protanopia and deuteranopia - makes you unable to tell the difference between red and green
Blue-yellow colour blindness
This is a less common type of colour blindness that makes it difficult to tell the difference between blue and green and yellow and red. The two types are:
- Tritanomaly - makes it difficult to tell the difference between blue and green as well as the difference between yellow and red
- Tritanopia - makes colours look less bright and makes it difficult to tell the difference between blue and green, yellow and pink, and purple and red
There are many different causes of colour blindness but the most common cause is genetic, meaning they are passed down from your parents. However, some types of colour blindness are acquired which means you develop the condition at some point in your life instead of being born with it. For example, damage to your eye or brain can cause colour blindness. Therefore, you have a higher risk of having colour blindness if you:
- Have a parent with colour blindness
- Have certain eye diseases like glaucoma or age-related macular degeneration (AMD)
- Have certain health conditions like diabetes or liver disease
- Take certain medication
Genetic causes of colour blindness
The most common cause of colour blindness is a genetic mutation (passed down from your parents). If a parent has a genetic condition it can be passed down to their children through groups of genes called chromosomes. The X and Y chromosomes determine whether you would be AFAB or AMAB. Individuals with two X chromosomes are AFAB whereas people with one X chromosome and one Y chromosome are AMAB. The genes that cause some types of colour blindness, such as red-green colour blindness get passed down on the X chromosome.1
This means that red-green colour blindness is more common in people AMAB. This is because people AMAB only have one X chromosome which is inherited from their mother meaning if that X chromosome has the gene for colour blindness then the individual will have colour blindness. People AFAB have two X chromosomes so both chromosomes would need to have the gene for red-green colour blindness in order for them to have the condition. This explains why there is a disproportionate prevalence of colour blindness between people AMAB (8%) and people AFAB (0.5%).1
Unlike red-green colour blindness, blue-green colour blindness and monochromacy are passed down on other chromosomes so they affect people AMAB and people AFAB equally.
Acquired causes of colour blindness
Colour blindness can also be acquired later in life when your eyes or a part of your brain that detects colour is damaged. This can be caused by diseases, injuries and certain medications.
Eye diseases such as glaucoma or age-related macular degeneration (AMD) can cause colour blindness.
Injuries to the eye or brain
Physical trauma, such as eye and brain injuries can also cause colour blindness. If the part of the brain that detects colour is damaged it can affect your colour vision.
Other diseases and health conditions
Certain diseases can also cause colour blindness. This includes diseases of the brain and nervous system, such as Alzheimer’s disease and multiple sclerosis. Other health conditions such as diabetes, liver disease and stroke can also contribute to the development of colour blindness. This type of acquired colour blindness can improve if the underlying disease/condition is treated.
Colour blindness may be a side effect of certain medicines taken for existing health conditions. This includes medicines that treat high blood pressure, nervous disorders, autoimmune diseases and heart problems, as well as antibiotics and barbiturates.
Studies show that colour vision declines more rapidly after the age of 70. This means that age is a great risk factor for acquired colour blindness as your colour vision may get worse as you get older. Therefore it may present itself as a symptom of degenerative diseases of the eye, such as age-related macular degeneration (AMD) or cataract.2
Differences between genetic and acquired colour blindness
Genetic colour blindness is inherited from your parents and it can either be mild, moderate or severe. This type of colour blindness usually affects both eyes and does improve or worsen over time. It also cannot be cured.
On the other hand, acquired colour blindness can develop at any point in your life and can vary in severity. This means that your symptoms may be mild and remain stable or they may progress in severity into a more serious form of the condition such as monochromacy. The cause of colour blindness usually determines how severe your symptoms will be, so the condition can sometimes be treatable based on the cause. Therefore it is important to identify the cause of colour blindness and whether it is inherited or acquired.
Diagnosis and treatment options
There are two main tests used to diagnose colour vision deficiency (colour blindness):
- The Ishihara test - you will be made to read images made up of coloured dots
- Colour arrangement test - you will be asked to arrange coloured objects in order of their shade
There is currently no treatment available to people who have genetically inherited colour blindness. However, this is not a major problem as this condition does not usually affect everyday life activities and people can adapt to seeing colours differently.
If your child has been diagnosed with colour blindness, it may interfere with their performance at school. It is important that you inform their school of your child’s condition so they can make adjustments for lessons and exams.
As an adult, being diagnosed with colour blindness may prevent you from pursuing certain careers for safety reasons, such as a pilot or train driver. However, most of the time, colour blindness does not cause serious problems.
Alternatively, if your colour blindness is acquired because of another health condition, your doctor will aim to treat that condition to improve your colour blindness. If your condition is caused by a certain medicine then your doctor may adjust how much you take or prescribe you a different medicine.
If your colour blindness is affecting your everyday tasks and activities then there are devices that can help you, such as:
- Glasses and contacts - these help you to tell the difference between colours
- Visual aids - uses technology to identify colours and help you with everyday tasks
In summary, colour vision deficiency or colour blindness is a condition which causes you to see colours differently than most people. This could mean you have difficulty seeing the difference between colours, the brightness of colours and the different shades of colour. There are different types of colour vision deficiency but the most common type is red-green colour blindness. Colour blindness can either be genetically inherited from your parents or acquired as a result of certain diseases such as diabetes or liver disease, injuries to the eye or brain, certain medicines or old age. Inherited colour blindness can either be mild, moderate or severe and does not improve over time whereas acquired colour blindness can change in severity. Genetically inherited colour blindness cannot be cured whilst acquired colour blindness can sometimes be cured depending on the cause. If your colour blindness is affecting your everyday tasks then using glasses, contacts or visual aids can be of help.
- Simunovic MP. Colour vision deficiency. Eye [Internet]. 2010 May [cited 2023 Apr 28];24(5):747–55. Available from: https://www.nature.com/articles/eye2009251
- Yada T, Tokumaru O, Eshima N, Kitano T, Yokoi I. Influence of aging on the color visual field in humans: A cross-sectional study. Medicine [Internet]. 2021 Dec 17 [cited 2023 Apr 28];100(50):e28230. Available from: https://journals.lww.com/md-journal/Fulltext/2021/12170/Influence_of_aging_on_the_color_visual_field_in.61.aspx