1 in 12 men (and a much lower percentage of women, 1 in 200) are colour defective, more commonly known as colour blind.
This does not mean that they can’t see colour; it means that they are less able to tell the difference between certain colours. It can cause confusion between colours that the rest of us find it easy to tell apart, such as reds, greens and yellows.
The Ishihara test for colour blindness
The Ishihara test is a colour perception test for red-green colour deficiencies, the first in a class of successful colour vision tests called pseudo-isochromatic plates (PIPs) and is just one way we can diagnose colour blindness.
The Ishihara test is the standard test for colour blindness and consists of coloured plates of dots on which a number can be seen.
Someone who is colour blind will either see a different number from someone who is not colour blind or will not see a number at all. However, there are some plates where someone who is colour blind will see a number and a non-colour blind person will not.
Unfortunately, being colour blind prohibits a person from certain professions, such as an electrician, pilot or commercial sailor.
Treatment for colour blindness
Colour blindness is incurable, however, it is possible to increase the number of colours a colour defective patient can tell apart by using a coloured filter in front of one eye. This allows the brain to compare between the two eyes and distinguish more colours. Most colour defective patients can then perform better on the Ishihara test as they are able to see more numbers.
To achieve this, it is possible to wear a specially tinted soft contact lens in one eye. Alternatively, the tint can be incorporated into special mirrored spectacles, either to prescription or as a clip-on. The visual improvement in colour perception and recognition by colour defective patients can be quite spectacular.
Contact Lenses for Colour Blindness
We use ChromaGen™ lenses – a unique system of coloured lenses of a specific density and hue that are worn as either contact lenses or spectacles. An amazing 97% of colour blind people reported a significant enhancement to their colour vision after trying these lenses. For many people suffering from colour deficiency, this improvement can be life changing. Even the colours they normally identify correctly may seem brighter, richer and more vivid, whilst they may perceive other shades and colours for the first time.
In order to try the coloured glasses or contact lenses, an hour-long assessment appointment is needed with Dr Caroline Burnett Hodd or Connan Tam. You may be asked to use a coloured contact lens or an overlay for an hour or two to see the effect and you can then decide whether to go further.
