COLOR BLINDNESS
Most of us see our world in color. We enjoy looking at a lush green lawn or a red rose in full bloom. If you have a color vision defect, you may see these colors differently than most people. Color blindness is not a form of blindness at all, but a deficiency in the way you see color. With this vision problem, you have difficulty distinguishing certain colors, such as blue and yellow or red and green. Color blindness (or, more accurately, color vision deficiency) is an inherited condition that affects males more frequently than females.
There are three main kinds of color vision deficiency. Red-green color vision defects are the most common. This type occurs in men more than in women. The other major types are blue-yellow color vision defects and a complete absence of color vision. Most of the time, color blindness is genetic. There is no treatment, but most people adjust and the condition doesn't limit their activities.
Color vision depends on the absorption of light by visual pigments contained within specialized cells in the eye called photoreceptors. There are two types of photoreceptors: rods and cones. Rods, which provide vision in dim light, have no ability to distinguish between colors. Cones are responsible for color vision. There are three different types of pigment in the normal eye. Color vision occurs within the visual part of the brain compares electrical signals from the different types of cones. Defects in color vision are either inherited or acquired. Inherited defects result mainly from missing or incorrect visual pigments. There are different types of inherited defects, with different levels of severity. Color vision defects sometimes can be acquired, as a result of eye disease or normal aging or as a side effect of certain medications. In acquired defects, other parts of the eye besides cones and cone pigments may be affected. Besides differences in genetic makeup, other causes of color vision defects or loss include:
1. Parkinson's disease (PD). Because Parkinson's disease is a neurological disorder, light-sensitive nerve cells in the retina where vision processing occurs may be damaged and cannot function properly.
2. Cataracts. Clouding of the eye's natural lens that occurs with cataracts can "wash out" color vision, making it much less bright. Fortunately, cataract surgery can restore bright color vision when the cloudy natural lens is removed and replaced with an artificial intraocular lens.
3. Tiagabine for epilepsy. An antiepileptic drug known as tiagabine has been shown to reduce color vision in about 41 percent of those taking the drug, although effects do not appear to be permanent.
4. Leber's hereditary optic neuropathy (LHON). Particularly prevalent among males, this type of inherited optic neuropathy can affect even carriers who don't have other symptoms but do have a degree of color blindness. Red-green color vision defects primarily are noted with this condition.
5. Kallman's syndrome. This inherited condition involves failure of the pituitary gland, which can lead to incomplete or unusual gender-related development such as of sexual organs. Color blindness can be one symptom of this condition.
Color blindness also can occur when aging processes damage retinal cells. An injury or damage to areas of the brain where vision processing takes place also can cause color vision deficiencies. Some people use special lenses to enhance color perception, which are filters available in either contact lens or eyeglass lens form. If your regular eye doctor doesn't handle these types of lenses, ask for a referral so that you can seek out someone who might be able to assist you. Meanwhile, there is no cure for color blindness. But some coping strategies may help you function better in a color-oriented world. Most people are able to adapt to color vision deficiencies without too much trouble. But some professions, such as graphic design and occupations that require handling various colors of electrical wiring, depend on accurate color perception.
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