| Oliver Sacks, in the Case of the Colorblind | | | | be very subtle which is why early reporting |
| Painter, describes how an artist, who was | | | | is essential.If you acquire color |
| famous for his brilliantly-colored abstract | | | | deficiencies you are more likely to encounter |
| canvasses, suddenly and irreversibly loses | | | | difficulties in correctly naming colors. |
| all color perception as the result of a car | | | | This is because life-long experience with |
| accident. This tragic case depicted by Sacks | | | | defective color perception enables those with |
| is one example of an acquired color vision | | | | the inherited form to use compensatory |
| deficiency.What were once vibrant works of | | | | techniques to overcome their handicap.Because |
| art now appeared to him grayish or black and | | | | acquired color vision deficiencies are the |
| white. It was a devastating blow for a | | | | result of life events, they can arise from a |
| lifelong painter whose art and life were now | | | | variety of different causes affecting the |
| without meaning. | | | | retina, visual pathways or areas of the brain |
| | | | which process color information.A wide range |
| Not all cases of this affliction, however, | | | | of prescription drugs, conditions such as |
| are as sudden, complete or permanent: onset | | | | multiple sclerosis, diabetes and |
| can be slow and appreciation of colors can | | | | cardiovascular diseases, some liver diseases |
| change gradually over time depending on the | | | | and many eye diseases can affect the cone |
| particular eye disease.However, whereas | | | | nerve cells which enable us to discriminate |
| inherited alterations to color vision tend to | | | | fine detail and colors by day.As a result, |
| remain stable through life, late onset color | | | | and often in only one eye at a time, color |
| vision changes can be an early sign of | | | | vision is temporarily or permanently changed. |
| disease or a side effect of prescribed | | | | Both men and women are affected |
| medication. It is important, therefore, that | | | | equally.Sufferers from arthritis, heart |
| you consult your doctor should you become | | | | disease and depression sometimes find their |
| aware of any changes in your perception of | | | | color vision impaired as a side effect of |
| color.To clarify matters, let's look at the | | | | their long-term use of prescription drugs. |
| differences between acquired color vision | | | | Even stroke patients who take aspirin over |
| deficiency and inherited or congenital | | | | many years to thin the blood can encounter |
| deficiencies:Typically congenital | | | | altered color perception.Cataracts, glaucoma |
| deficiencies involve confusion over red and | | | | and the majority of eye problems affecting |
| green. Acquired deficiencies more often than | | | | the retina or nerve pathways to the brain are |
| not are a blue-yellow problem.There is a | | | | associated with a reduced ability to |
| gender imbalance in congenital defects as | | | | differentiate colors, including blues and |
| they are linked to the X female chromosome. | | | | greens.But the most widespread form of |
| This means mothers (whose vision will be | | | | acquired color vision deficiency in the |
| apparently normal) carry the defect to their | | | | developed world, affecting some 23 per cent |
| sons. Inherited color vision deficiency is, | | | | of people over the age of 65, is age-related |
| therefore, more prevalent in males than | | | | macular degeneration (AMD). Involving a loss |
| females.By contrast, acquired defects are not | | | | of the cone-rich area of central vision (the |
| gender-related except by gender differences | | | | macula) where color vision is sharpest it |
| in the experience of brain trauma injuries, | | | | often leads to blindness.Finally, the |
| for example.As touched on above acquired | | | | condition known as optic neuritis, which can |
| defects are less likely to be stable over | | | | result in a distortion or lack of color |
| time. With congenital defects both eyes tend | | | | vision, illustrates well how one example of |
| to be affected equally whereas acquired color | | | | acquired color vision deficiency can be an |
| deficiencies are more likely to affect one | | | | indicator of two very different |
| eye more than the other. Stroke victims | | | | prognoses.This inflammation of the optic |
| typically experience a more pronounced color | | | | nerve is sometimes diagnosed in young |
| deficiency in one eye.Acquired defects are | | | | children following an illness such as measles |
| not as easily diagnosed or detected with | | | | or mumps. |
| standard color vision tests. The changes can | | | | |