The human eye is like a camera and one of the essential parts is the lens. The lens usually remains clear, but mainly due to age, the lens may become cloudy and light is unable to pass through normally. This may happen in either one or both eyes. This is what is known as a cataract.
Colour deficiency occurs in 7% of males in any race. It is extremely rare in females and is genetically inherited. It is recessive in a female which means that they can pass it on to their sons but they rarely display the problem themselves.
The vast majorities of people with colour deficiency has this from birth and are colour deficient in the red/green area. These individuals are called protanopes. The condition is not progressive and is never acquired. People who have an acquired colour vision defect will have some ocular pathology and will require further investigation. An example of this is optic neuritis which can be the presenting symptom of neurological conditions such as multiple sclerosis.
The standard test for detecting red/green colour defects is the Ishihara test (see below).
More involved tests are available at centres for patients with colour defects. There is no cure for patients with colour deficiency. Recently there has been some publicity about corrective lenses for colour deficiency. These are called Chromogen lenses which are available in both spectacle and contact lens form. Initially people felt that this did correct the problem as patients passed the Ishihara test when wearing these lenses however further investigation concluded that the area of colour deficiency was just shifted along the spectral band.
If you would like further information about colour deficiency or Chromogen lenses you could contact The Institute of Optometry, Newington Causeway, Elephant and Castle, London. Tel: 0207 407 4183
Colour Deficiency test (Ishihara Test)
(Please read the disclaimer, with reference to test accuracy)
By joining up the dots of a similar colour on each chart it should be possible to view a number. This test is designed to pick up people who have congenital red/green colour deficiency. If no number is viewed it is likely that you have this colour deficiency.
This is the test image, the number 12 should be visible to all.
On Test plate number 1 patients with normal colour vision will see a number 8.
Test plates 2,3 and 4 will give an image of a number 3, 73, and 42 respectively
Test Plate 1
Test Plate 2
Test Plate 3
Test Plate 4
All information is for reference purposes only. If you have any concerns we recommend that you visit a qualified optician.