CVD is also known as colour blindness. The eyes are unable to detect certain colours and find it difficult to tell the difference between colours. It does not affect visual acuity (the ability to see clearly) and is caused with a problem with the cone cells in the retina. It is most commonly genetic but can develop as a result of an underlying health condition, medication side effect or the ageing process.
Red/green CVD is the most common and is inherited. It is easily picked up during an eye exam using colour vision tests. Blue/yellow CVD is quite rare, can be inherited or caused by other health conditions.
Achromatopsia is a rare condition where a person has difficulty seeing any colour, and will also have blurred vision, sensitivity to bright light and may cause nystagmus.
For help, contact the Colour Blind Awareness Service www.colourblindawareness.org or the RNIB helpline 0303 1239999