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Description

Colour Vision Deficiency (also known as colour blindness) is a condition which limits a person’s ability to recognise and differentiate between different colours. It affects approximately one in twelve men and one in every one hundred women. There are three different forms of the condition which can affect recognition of some colours (red-green deficiency and blue-yellow deficiency) or all colours (total colour deficiency).

People with mild colour deficiencies learn to associate colours with certain objects and are usually able to identify colours very well. However, they are unable to appreciate colour in the same way as those with normal colour vision. People who have complete (known as total) colour vision deficiency often have other serious eye problems.

Symptoms

There are three major types of colour vision deficiency. The most common is called red-green deficiency, where a person has difficulty in distinguishing both of these colours. Blue-yellow deficiency is less common and refers to when a person has difficulty in distinguishing between blue and yellow. Total colour vision deficiency, also known as achromatopsia, refers to when a person’s vision is restricted to only seeing white, black and grey.

The symptoms of colour vision deficiency are dependent on several factors, such as whether the problem is congenital, acquired, partial, or complete. In cases of more serious inherited or acquired colour vision problems, symptoms may include reduced vision, nystagmus (rapid involuntary movement of eyes) or appearance of objects in various shades of grey (this occurs with complete colour blindness and is very rare).

Causes

Photoreceptors called cones allow us to appreciate colour. These are concentrated in the very centre of the retina and contain three photosensitive (light sensitive) pigments: red, green and blue. People with red-green vision deficiency have limited or no function of the red cone and green cone photosensitive pigments. People with blue-yellow vision deficiency have limited or no function of blue cone photosensitive pigments. Individuals with total colour deficiency have very little (if any) cone photosensitive pigments.

Colour vision deficiency can be inherited or it may be caused by other health conditions.

Inherited colour vision deficiency is most common affecting both eyes. Changes in DNA which give rise to colour vision deficiency are linked to the X chromosome. The presentation of the condition can vary from mild to severe, but generally does not worsen over time.

Other health conditions can lead to a colour vision deficiency. This includes diseases of the optic nerve or retina, diabetes, age-related macular degeneration, glaucoma and cataracts. In such cases, colour vision problems might only affect the eye with the disease. However, such cases may become progressively worse over time. Some medications and chemicals have also been linked with this condition.

Diagnosis

Colour vision deficiency is detected through a series of colour vision tests.

One of the most common tests uses special coloured charts known as Ishihara Test Plates. On each plate is a number composed of coloured dots. While holding the chart under good lighting, the patient is asked to identify the number. Individuals may also take the arrangement test. In this examination, a person will be asked to arrange different coloured objects in the order of their colour shade/hue. Once the colour defect is identified, more detailed colour vision tests may be performed.

Treatment

Currently, there is no treatment for colour vision deficiency, but researchers are working to change this. To find out more about these advances, please visit the latest research section.

There is a wide range of assistive technologies for people living with this condition. These include visual aids and phone apps which help with identifying colours type and shade.

General eye check-ups are important for people with colour vision deficiency, as these individuals may still be at risk of developing other kinds of eye problems that affect the general population, some of which may be treatable.

No matter what level of vision a person may have, it is important to look after the eyes. To find out more about what can be done to take care of the eyes on a daily basis, please visit our Tips for Good Eye Health.

Research

Researchers are actively searching for ways to treat colour vision deficiency. Much of this effort has focused on developing gene therapies, although other therapeutic avenues have been investigated.

There are clinical trials ongoing which are examining gene therapies for total colour vision deficiency. Gene therapy is a therapeutic approach which has proven safe in other retinal conditions. Using this technique, researchers have engineered small, safe viruses which aim to deliver the correct version of the gene of interest to the light sensing photoreceptor cells in the retina. These interventions are currently being examined in clinical trials for their safety and efficacy (measuring ability to produce desired effect) in humans.

Information about clinical trials can be found on the clinical trials website and can be searched by condition and trial location.

Support

Receiving a diagnosis can be overwhelming for anyone, but this is not a journey that you have to make alone. There are many groups and resources available to provide support for people living with colour vision deficiency.

Fighting Blindness offers a free and confidential counselling service (Insight Counselling). For further information please contact insight@fightingblindness.ie or call 01 6746496.

A mindfulness group is also available on every Wednesday at the Fighting Blindness office at 11am.

For technology support and guidance, the Dublin-based Technology Exchange Club meets every Monday at the Fighting Blindness office at 11am. Another Technology Exchange Club, based in Cork, meet every Saturday in the Cork City Library, Grand Parade, Cork City at 11am. The Cork-based club do not meet on Bank Holiday weekends or on the second Saturday of the month. For further information please contact insight@fightingblindness.ie or call 01 6746496.

Resources

Féach provides support for parents of children living with sight loss in Ireland.

ChildVision is the national education centre for children with sight loss in Ireland.

NCBI (National Council for the Blind in Ireland) provides support and services for people living with sight loss in Ireland.

Irish Guide Dogs for the blind helps individuals and their families to achieve improved mobility and independence.