Color Blindness


Types of Color BlindnessThere are many types of color blindness, including:

  • Anomalous Trichromacy is the condition in which the color-sensitive cones are damaged, preventing you from being able to identify certain colors. One type of anomalous trichromacy is protanomaly, in which L-cone damage causes trouble perceiving reds. Another type is deutanomoly, in which M-cone damage prevents normal perception of greens. 

  • Dicromasy is a type of color blindness that results from the complete lack of one type of cone. Dicromasy is a much more severe problem than anomalous trichromacy.

    The various types of dicromasy are based on the cone that you are missing. For example, if all your L-cones were missing, a condition known as protanopia, you would not be able to perceive colors in the red wavelengths. If you lacked M-cones, you would have deutanopia and would not be able to see greens wavelengths. If you didn’t have S-cones, you would not be able to see blue wavelengths and would have tritanopia.

  • Monochromacy occurs when an individual is missing or has defective cones in two or three of the cone types. Those suffering from monochromacy can’t discern more than a few colors, if any at all. Monochromacy is the most severe type of color blindness.Tests for Color BlindnessWhen it comes to diagnosing color blindness, doctors can use one or a combination of three existing diagnostic tests, including:

  • Ishihara test: One of the most commonly used tests for color blindness is the Ishihara Color test, developed in 1917, that measures red and green deficiencies.

    The Ishihara tests consist of plates that use multiple colored dots of various sizes with a number "hidden" color spots within the dot pattern. When a person with normal vision looks at one of these dotted cards, he sees a circle filled with red dots, as well as dots of other colors that form a number in the middle of the circle.

    While those suffering from protanomaly (the inability to see red) will see a number different than the one that those with normal vision will see, those suffering from deutanomoly (the inability to see green) see yet another number. Thus, this test not only identifies the presence of color blindness but also the type of color blindness a person has.

    However, because the Ishihara test revolves around identifying numbers, it isn’t the best way to diagnose children. More commonly, color blindness tests for children call for kids to recognize shapes of different colors. 

If you suspect that you or your child are color blind, schedule an exam with your optometrist or ophthalmologist. Your doctor can teach you tools and techniques that can help you cope with this condition.

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