Colour vision deficiency — commonly known as colour blindness — affects approximately 1 in 12 men and 1 in 200 women in the UK. The most common type is red-green colour deficiency, where certain shades of red and green appear similar or are difficult to distinguish. Total colour blindness (seeing in greyscale) is extremely rare.
Colour vision testing is usually included as part of a standard eye test at no extra charge, particularly for children and for adults who have not been tested before. The most common screening tool is the Ishihara test, which uses plates covered in coloured dots with numbers or patterns hidden within them. People with normal colour vision see the numbers clearly, while those with a deficiency may see different numbers or none at all.
If the Ishihara test suggests a colour vision deficiency, more detailed tests may be used to determine the exact type and severity. These include the Farnsworth D-15 test, the City University Test, and in specialist settings, the anomaloscope. Knowing the precise nature of your colour deficiency is important if you are pursuing a career that requires specific colour vision standards.
Careers affected by colour vision requirements include the armed forces, police, fire service, aviation (pilots, air traffic controllers), maritime (deck officers), electrical engineering, train driving, and some healthcare roles. If your career requires a colour vision certificate, your optometrist can provide the appropriate assessment and documentation.
There is currently no cure for inherited colour vision deficiency. However, awareness and practical strategies can make a significant difference. Some people find tinted filters or specific spectacle tints helpful in certain situations, though these do not restore normal colour vision. For children, early detection allows teachers to make adjustments — such as labelling colours on classroom materials and avoiding colour-coded information where possible.