A color vision test, also known as the Ishihara color test, measures your ability to tell the difference among colors. If you do not pass this test, you may have poor color vision or be considered “colorblind.” However, true “colorblindness” is a very rare condition in which you are only able to see shades of gray.
Causes of Poor Color Vision
The most common form of poor color vision is an inability to distinguish shades of green from red. Genetics, aging, certain medications and diseases, and exposure to chemicals can cause poor color vision. It is statistically more likely to occur in men than women.
Often, problems with color vision are due to a disease affecting your optic nerve, such as glaucoma. Poor color vision can also be the result of an inherited problem with the cones (color-sensitive photoreceptors) in your retina. The retina is the light-sensitive layer at the back of your eye.
Certain diseases, including diabetes, alcoholism, macular degeneration, leukemia, Alzheimer’s disease, Parkinson’s disease, and sickle cell anemia can cause color vision impairment. Your color vision may improve if you receive treatment for the underlying condition.
You may want to have a color vision test if you think that your color vision is deficient. If your child is receiving an eye exam, it is a good idea to have him or her tested for both color vision and visual acuity. This can help address any potential problems early and effectively.
Preparation for a Color Vision Test
If you or your child wears glasses or contact lenses, these should be worn during the exam. Your doctor will ask if you have been taking any medications or supplements, if you have any medical conditions, and if there is a history of poor color vision in your family.
There are no risks associated with this test and no special preparation is required.
How a Color Vision Test is Performed
Your eye doctor will administer the test. You will sit in a normally lit room. You will cover one eye, and then with the eye that is uncovered, you will be asked to look at a series of test cards. Each card contains a multicolored dot pattern.
There is a number or symbol in each color pattern, and you will be asked to identify it, if you can. Numbers, shapes, and symbols should be easy to distinguish from their surrounding dots if you have normal color vision. If you have color vision impairment, you might not be able to see the symbols at all or will have difficulty distinguishing patterns among the dots.
After checking one eye, you will be asked to cover that eye and look at the test cards with the other. The doctor may ask you to describe a particular color’s intensity as perceived by one eye versus the other. It is possible to have a normal result on the color vision test but still experience a loss of color intensity in one eye or the other.
Understanding the Test Results
There are several color vision problems that this test can help pinpoint:
- protanopia: difficulty distinguishing blue from green and red from green
- tritanopia: difficulty distinguishing yellow from green and blue from green
- deuteranopia: difficulty distinguishing red from purple and green from purple
- achromatopsia: complete color blindness (a rare condition, in which only shades of grey are visible)
After a Color Vision Test
There is no treatment that directly addresses color vision problems. However, if your color vision deficiency is being caused by an illness, such as diabetes or glaucoma, addressing the illness may improve your color vision.
Using colored filters on your eyeglasses or colored contact lenses might make color contrasts easier to see. However, neither a filter nor colored contacts will improve your innate ability to tell colors apart.