How the Eye Sees Color
Color blindness is a visual deficiency that is characterized by the inability to see certain colors. To understand how this condition affects the eye, it is necessary to understand how the eye perceives color.
The eye operates like a camera with the lens in the front, focusing images onto the retina located in the back of the eye. The retina is covered with special nerve cells called rods and cones. The rods and cones are photoreceptors that contain color-sensing materials called pigments that react when exposed to light. These pigments are red, green and blue. It is the cones that are responsible for color vision, and they their various pigments absorb different wavelengths of light. Rods only have one type of pigment and cannot detect color. However, when the rods and cones work together we are able to see a wide spectrum of light, which our eyes interprets as different colors, according to the Cleveland Clinic. People with normal vision are called trichromats (having all three pigments).
The eye will not be able to see all of the colors if there are pigment abnormalities or if certain types of pigment are missing. People with color blindness have a deficiency or total lack of one or more photosensitive pigments of the cones. The most common type of color vision problem is a deficiency in one of the three pigments. People with this condition are called anomalous trichromats, and those who completely lack one of the pigments are called dichromats, according to St Luke's.
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Most people with color blindness have difficulty distinguishing between reds and greens, while some others cannot perceive blues and yellows. Those with blue-yellow color blindness usually cannot see reds and greens as well.
Causes of Color Blindness
Color blindness is mainly considered to be a genetic condition that is usually passed on from mother to son through the X chromosome. It is a relatively common condition that affects approximately 1 out of every 10 men in varying degrees. Some women also inherit color blindness; although this is rare, and only 0.4 percent of the female population experiences this condition. Color blindness can also be caused by diseases of the retina or optic nerve or by the drug hydroxychloroquine, used to treat rheumatoid arthritis. However, the inherited version of color blindness is much more common.
Inherited color blindness affects both eyes and remains the same throughout life. It does not worsen with time. It is usually partial and only affects the ability to see some colors. Complete color blindness, or achromatopsia, is very rare and is usually accompanied by other serious eye problems as well, according to the University of Maryland Medical Center.
Detection and Treatment
If you suspect that you have a color vision deficiency, schedule an appointment with an ophthalmologist. Color blindness is normally detected with colored charts called Ishihara Test Plates. Each plate is made from different colored dots and contains a number. Upon viewing the plates, if you are unable to discern the number, it is likely that you have a color vision deficiency. Although there is no cure for color blindness, most people with mild deficiencies learn to associate objects with certain colors and can identify color in this way.
