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What You Need to Know About Color Vision Deficiency

November 4, 2017

Rods and cones are photoreceptors that sit on the retina and pass information to the brain. Rods are responsible for light and cones are responsible for color. Colorblindness is related to the photoreceptors available in your eye and is largely genetic. The term “color blindness” leads you to believe that people who are colorblind see the world in black and white. This isn’t the case. More than 99% of all colorblind people can actually see color. Because of this, experts believe the term “color vision deficiency” (CVD) is more accurate than the term colorblind.

CVD is quite common with a little more than 8% of men in the world suffering from CVD. Women rarely have CVD (about 0.5%). There are four main types of CVD and each can range in severity from mild to severe.

The Ishihara test is the most common test for red-green colorblindness. This test involves tiny red and green dots in a circular pattern that form a number. Only someone without a red-green CVD can read the number.

Another test for CVD is the Cambridge Color Test. This test uses computers to screen for color vision deficiencies and examine more detailed changes in color discrimination as a result of congenital or other conditions.


Deuteranomalia, also known as red-green colorblindness, is the most common form of CVD where those affected sometimes don’t even realize they have CVD. Colors appear more subdued than a normal color palette, especially for shades of red and green. Deuteranomalia is found in 4.63% of men and 0.36% of women.


In this form of CVD, all shades of red and green look substantially faded where shades of blue and yellow are much less affected. Protanopia is present in about 1% of men.


In the case of Tritanopia, people see all colors with a greenish or pinkish hue. The blue-yellow photopigments of the patient’s color-identifying portion of the cone cells in their retina are either completely missing or have some sort of mutation. This rare form of CVD, also called blue-yellow colorblindness, affects only 0.0001% of men and women.


Monochromacy is the most rare form of CVD. People who have Monochromacy can only see in black and white. Monochromacy occurs when people have no cones or only one type of cone.

You can view several photos here that compare the effects of the above forms of CVD.

There is no cure for CVD but there are new solutions available to help people with CVD cope with the challenges they face. Special lenses made by Oxy-Iso are available that help correct CVD for patients that have red-green CVD. There are also apps available that help someone with CVD determine what color something actually is by taking a picture with their cell phone and using the app.

Some software and video game companies are now offering user interfaces appropriate for people with CVD or colorblind modes so people with CVD can still use the software or play the game effectively.

Many people don’t realize they have any form of CVD but if you’re worried that you may have a color vision deficiency, contact OCLI today to schedule a simple eye exam. 

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