What is Color Blindness?
Color blindness, or color vision deficiency, is an eye condition that causes an inability to distinguish certain colors or shades of colors to some degree. Color blindness does not mean that a person can only see black and white. A person with color blindness is able to see colors, but they are not able to distinguish some colors from others. Color blindness is a hereditary condition, but it can also be caused by eye diseases, damage to the retina and macula, aging, or cataracts. Although there is no real treatment for hereditary color blindness, there are ways to cope with it. For example, there are special glasses that can help people with color blindness distinguish between different colors, even if they cannot truly see them. If you have trouble seeing the number in the picture below or are not able to see it at all, then you may have some degree of color blindness.
Color Blindness Symptoms
Symptoms of color blindness vary from person to person. Many people who are colorblind have trouble seeing how bright colors appear to be. Other people are unable to tell the difference between similar colors. Many experts believe symptoms of color blindness may be so mild in some people that they are unaware of their condition. Parents may notice that their child is colorblind only if the child performs poorly at certain learning activities.
What causes Color Blindness?
The retina contains rods and cones that help us to see objects in different colors and varying degrees of brightness. The cones are photoreceptors that allow us to distinguish among colors and different shades of these colors. The cones contain light-sensitive pigments that are particular to a range of wavelengths. There are three different types of cones, one of which is sensitive to short wavelengths, or the color blue; one sensitive to medium wavelengths, or the color green; and the other sensitive to longer wavelengths, or the color red. When the cones are unable to distinguish differences among these wavelengths, we see that color range differently. The absence of the cones responsible for green and red hues can also affect sensitivity to brightness. Red-green color blindness is more common than blue or yellow color blindness.
Color blindness is usually hereditary, meaning that we are born with it. Age can also diminish our color sensitivity, but usually not to the extent that occurs with hereditary color blindness. Damage to the retina from eye diseases or injury may also lead to color blindness.
Common eye diseases that may affect color vision include:
- Leber’s hereditary optic neuropathy
- Macular degeneration
- Parkinson’s disease
- Retinoblastoma (seen in children)
Occasionally, medications may affect one’s color vision. Common medications known to do this include:
- Oral contraceptives
- Hydroxychloroquine (Plaquenil)
- Viagra (can cause disturbances in blue vision—ironically, the color of the pill itself)
Types of Color Blindness
- Anomalous Trichromacy: A mild shift in the sensitivity of the cones
- Protanomaly: Shades of red appear weaker in depth and brightness
- Deuteranomaly: Shades of green appear weaker
- Tritanomaly: A very rare condition in which shades of blue appear weaker
- Dichromacy: Severe deficiency or complete absence of one of the types of cones
- Protanopia: Shades of red are greatly reduced in depth and brightness, if they can be seen at all
- Deuteranopia: Shades of green are greatly reduced in depth and brightness, if they can be seen at all
- Tritanopia: A very rare condition in which shades of blue are greatly reduced in depth and brightness, if they can be seen at all
Color Blindness Test
There are a few methods for color blindness testing. The most used is the Ishihara test. This test involves the use of pictures containing circles filled with bubbles in shades of the colors to be tested. The bubbles form the shapes of numbers that colorblind people will not be able to distinguish. Samples of these plates are pictured above in the “Types of Color Blindness” section. A more complex test is the Farnsworth-Munsell 100 hue test, in which a person must place numerous colored tiles of varying hues in order. To take a color blindness test, please visit http://www.colorvisiontesting.com or http://www.iamcal.com/toys/colors/index.php
Viewing the World with Color Blindness
The preceding images were provided courtesy of Terrace L. Waggoner, O.D. More information on color blindness can be
found on http://www.colorvisiontesting.com/
Color Blindness Treatment
Because color blindness usually does not affect the clarity of eyesight, treatment for it is usually limited. Usually your eye doctor will make a note of it in your records, making sure you aware of the condition and advising you not to take jobs that require accurate color matching, such as an electrician who needs to distinguish color-coded wires, or a pilot who uses color-coded instrument panels and must be able to see colored runway lights.
In some cases, a special contact lens can be worn. One gas-permeable contact lens that is a deep red in color may be sufficient. This type of contact lens is called an X-chrome, and it may assist you in passing a standard color-vision test. Although it does not cure the color vision deficiency, it does help. Vitamin A is known to benefit the cones in the retina, and although no conclusive studies have been done, taking this supplement may be beneficial to the overall health of your eyes.
Prognosis for Color Blindness
Unfortunately, color vision deficiency is a lifelong condition. Most people are able to adjust to their disability or use devices such as the “X-chrome” contact lens to find relief.
Talking to Your Eye Doctor
Here are some questions to ask your eye doctor about color blindness:
- Which tests will you use to determine if I’m colorblind?
- Which treatment options do I have?
- Are there any new treatment methods you are aware of?
- How often should I come in to see you?
- What do you think about the X-chrome contact lens?
- Do you prefer one treatment method over another?
- J. Anshel, MD “Smart Medicine for Your Eyes” (SquareOne Publishers, 2011) 182-184
- J. DiGirolamo, MD “The Big Book of Family Eye Care” (Basic Health Publications, 2011) 104-106