Color blindness ranges from the inability to distinguish similar shades of a color, to the complete inability to see color. Dyschromatopsia refers to the ability to see some colors, but not others. Achromatopsia, which is rare, refers to the inability to see colors at all.
Most of the time, color blindness is a genetic defect that is present when the individual is born. Less commonly, color blindness occurs as part of aging or is caused by a medication or disease.
An individual with achromatopsia cannot tell the difference between colors. Some people with achromatopsia can only see shades of gray. A person with this condition usually has poor distance vision, light sensitivity, and rapid eye movement.
Dyschromatopsia is the more common form of color blindness. Individuals with this condition usually have excellent vision. The person usually cannot tell the difference between shades of red and green. In rare cases, the person cannot tell the difference between shades of blue and yellow. Most persons with the condition are unaware that they are color blind.
Color blindness is usually caused by an inherited trait. Dyschromatopsia, or the inability to see some colors, occurs in about 8% of men and less than 1% of women. This difference occurs because the involved gene is carried on the X chromosome. Women with a defective gene usually have a normal color vision gene on their other X chromosome, and thus have normal color vision but are "carriers" and have a 50 percent chance of passing the abnormal gene to their sons. Men, because they only have one X chromosome, will manifest the colorblindness condition if the gene is abnormal.
Rarely, color blindness may also be caused by some medications Disorders of the retina of the eye, or of the optic nerve from the eye to the brain, may also interfere with color perception.
In general, there is no way to prevent color blindness. Regular eye exams and prompt treatment of eye disorders may help prevent some cases of color blindness.
Achromatopsia may not be uncovered until a child is 3 to 5 years old. To confirm the self-diagnosis, the healthcare professional usually performs a color test. Common tests include the HRR pseudoisochromatic plates or the Ishihara plates. The diagnosis of achromatopsia is sometimes determined by performing an electric eye test. This test is called an electroretinograph.
Color blindness is a lifelong condition. It is important to determine color blindness as early as possible. Individuals can be taught to cope with employment, hobbies, and games that require more exact color vision. Red-green color blindness is by far the most common form of color impairment. It may interfere with qualifying to fly a plane, pilot a commercial ship, or work in electrical repairs.
Color blindness is not contagious, and poses no risk to others. It is an inherited trait in most cases. Genetic counseling may be helpful to families with a history of color blindness.
There are no known medical, surgical, or nutritional treatments available for color blindness. Individuals with dyschromatopsia can see the difference between bright red and green, as in traffic lights. Adaptive equipment and techniques can be used to provide cues to the person with color blindness. Wearing dark lens glasses can sometimes help individuals with achromatopsia.
There are no side effects to the adaptive equipment and techniques used to help a person with color blindness.
Color blindness is a lifelong condition.
Routine exams are not needed once the diagnosis is made.