Overview of color vision test
A color vision test, also known as the Ishihara color test, measures your ability to tell the difference among colors. If you don’t pass this test, you may have poor color vision, or your doctor may tell you that you’re color blind. However, being truly color blind is a very rare condition in which you’re only able to see shades of grey.
Preparation for a color vision test
If you wear eyeglasses or contact lenses, you must continue to wear them during the examination. Your doctor will ask if you are taking any medications or supplements, whether you have any medical conditions, and whether 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.
What happens during a color vision test?
Your ophthalmologist will perform the test. You will be sitting in a naturally lit room. You will cover one eye, and then, with the exposed eye, you will look at a series of test cards. Each card contains a multi-coloured dot pattern.
There is a number or symbol in each color pattern. If you can determine the number or symbol, you will tell the doctor. Numbers, shapes, and symbols should be easy to distinguish from their surrounding points if you have natural color vision.
After examining one eye, you will cover the other eye and look at the test cards again. Your doctor may ask you to describe the intensity of a specific color as perceived by one eye versus the other. It is possible to get a normal result on a color vision test but still have a loss of color intensity in one eye or the other.
What do the results mean?
This test can help pinpoint several color vision problems, including:
- 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).