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Types of Colorblindness

Recognizing The Types of Color Blindness

A person who is color blind cannot discern different colors due to an abnormality in certain photoreceptors called cones. There are three different types of cones found in the retina, each sensitive to red, blue, or green; these are the L-cones, S-cones, and M-cones, respectively. Along with other photoreceptors called rods, they transmit information to our brain upon receiving light.

While rods are responsible for our night-vision, it is the cones which allow us to perceive various colors by way of light-sensitive pigments they contain. Our genes are responsible for the coded instructions these pigments require, so any abnormalities among these genes results in one form or another of color blindness, and the condition can be mild or severe.

Listed below are various types of color blindness and their description.

1) Monochromatism

Monochromatism is referred to as either rod monochromasy or cone monochromasy. In rod monochromasy, no cones are present at all, and this is characterized by a complete lack of color perception. Afflicted individuals see only black, white, and shades of gray; they often have poor vision and an extreme sensitivity to light.

In cone monochromasy only one cone type is present, either the red, blue, or green one; afflicted individuals may otherwise have decent vision in full light, but are still unable to distinguish any colors.

2) Dichromatism

In dichromatism there are only two of the three cone types present. In protonopia the red cones are missing, causing the sufferer to confuse red with green, sometimes causing it to appear bluish. In deuteranopia the green cones are missing, causing a similar affliction; the sufferer is insensitive to green and perceives mainly hues of yellow and blue. In tritanopia there are no blue cones, so those afflicted have trouble discerning blue and yellow hues.

3) Anomalous Trichromatism

With this condition all three cones are present but one is deficient, causing those afflicted to perceive certain colors to a greater degree than others. As with dichromatism, either the red, green, or blue cones may be affected, but the resulting condition is generally less serious.

In protanomaly the red cones are deficient, and in deuteranomaly the green cones are deficient; these two types are among the most common, and often called red-green color blindness.

In tritanomaly the blue cones are deficient, thus affecting the appearance of blue and yellow hues, but this affliction is quite rare.

Color blindness is often inherited, usually passed down through an X chromosome, and for this reason males tend to be more susceptible to the more common forms, such as the red-green varieties. This is due to females having two X chromosomes, which must both be afflicted to cause the condition, whereas males will display the condition if only their single X chromosome carries the gene.

Other causes of color blindness include diseases such as cataracts, glaucoma, macular degeneration, and retinal damage due to diabetes. In rarer cases the cause may be a side effect of medication or damage to the retina via an accident or stroke.

For more information on colorblindness treatment, please contact Dr. Thomas Azman.