Color Vision Deficiencies/Blindness
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Humans have 3 color individual photoreceptors in our retina, blue, red and green, and another type, the rods which respond to motion and dim illumination. Each photoreceptor has only one type of photopigment in it. The molecules inside our cones (photopigment) that respond to different wavelengths of light are a very complex molecule and are produced on multiple chromosomes for each of the photopigments. Any deficiencies in any of the parts that make up each cone’s photopigment can result in an abnormal but still functioning photoreceptor (color deficiency) or a lack of response to light (color blindness). Color vision deficiency is a term that is used to describe one of a number of hereditary or acquired color vision problems. The inherited form is the most common deficiency. It affects both eyes and does not worsen over time. This type of color vision deficiency occurs more in males than in females. Here is a graph of each photopigments response to varying wavelengths in nanometers (NM)of light;
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For a given wavelength of light falling onto our retina, the different responses of each of the 3 cones to that wavelength are interpreted by our brain as that particular color. If one of the photopigments isn’t responding correctly, it throws off our brain’s interpretation of that color (and all the other wavelengths) so we would not “see” all color as a normal functioning retina would. There can be also problems with the brain interpreting the retina’s signals but this isn’t discussed much in the literature.
Those people with normal color vision are referred to as trichromats. Color vision deficiencies may be partial (affecting 1 or 2 cones) or complete (affecting all 3 cone photoreceptors). Complete color deficiency, also known as color blindness, is rare and leaves only the rods for our vision. More often, individuals have a deficiency (not an absence) with one of the three photosensitive pigments in the eye: red, green or blue. People with a deficiency but still having all 3 photopigments are called anomalous trichromats, the most common type of color vision deficiency. With an abnormal but functioning red cone, the person is termed an anomalous protanomaly, abnormal but functioning green cone is termed an anomalous deuteranomaly, and an abnormal but functioning blue cone is termed an anomalous tritanomaly. A dichromat has a complete absence of one of the cone’s pigments with Protanopes missing the long wavelength (red) cones, Deuteranopes missing the medium wavelength (green) cones and tritanopes missing the short wavelength (blue) cones. Confused yet?
The most common signs of color vision deficiency are difficulty distinguishing between reds and greens or difficulty distinguishing between blues and greens. There is no cure for color vision deficiency but some special glasses can help by altering the light coming into a person’s eyes. However, those with mild color vision deficiencies can be taught to associate colors with certain objects. In some cases, color vision deficiency can affect child development and career choice, which is why early detection is critical.​​
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This web site has taken most of its information from the American Academy of Ophthalmology’s Preferred Practice Patterns publications. Each person’s medical condition is unique and all information should be reviewed with their ophthalmologist before deciding on any course of action. We cannot be held responsible for any use, misuse or outcomes from the information contained herein. Thank you.​