There are two types of cells in the retina that detect light – rods and cones. Rods detect light and dark, cones detect color. The brain uses input from the cone cells, which comes in three types of colors – red, green, and blue – to determine our color perception. Color blindness occurs when one or more of the color cone cells are not functioning as they should.
There are varying degrees of color blindness. Those with mild color blindness, can see colors normally in good light, but have difficulty in dim light. Others can distinguish certain colors in any light. The most severe form of color blindness is when everything is seen in gray, which is not as common.
Who Gets Color Blindness?
- Most people with color blindness are born with it. This is called a congenital condition, which usually passes from mother to son.
- Men are much more likely to be colorblind than women (10% of men vs. .5% of women).
- Conditions such as glaucoma, macular degeneration, Parkinson’s disease, leukemia and Alzheimer’s may increase the risk of color blindness.
How is color blindness diagnosed?
Eye care professionals provide various tests to diagnose color blindness.
- The Ishihara Color Test is the most common, which consists of a series of colored circles, each of which contact a collection of dots in different colors and sized. Within the circles are dots that form a shape clearly visible to those with normal color vision. However, it will be nearly invisible to those with red-green blindness.
- The Cambridge Color Test is similar to the Ishihara Color Test, except it is displayed on a computer screen. The patient is asked to identify a C shape that is different in color from the background and presented in one of four orientations. When seen, the patient is asked to press of four keys that correspond to the orientation.
- The HRR Psuedoisochromatic Color Test is another red-green blindness test that uses color plates to test for blindness
- The Farnsworth-Munsell 100 Hue Test uses blocks that are shades of the same color. The patient is asked to arrange them in the order of shade or hue. It tests the ability to recognize subtle color changes.
- The Anomaloscope tests two light sources coming from a circle. The top half of the circle is a yellow light and the bottom half is a combinations of red and green lights. The patient is asked to use a knob to adjust the brightness of the top half and the color of the lower half. The purpose is to make both halves the same brightness and color.
Is There Treatment for Color Blindness?
There is currently no cure for color blindness and it usually does not cause a significant disability. People with certain types of color blindness can use special lenses to help them identify color, but the lenses can only be used outdoors in bright lighting. Visual aids, such as phone apps, have also been developed to help people with color blindness. For example, users can snap a photo and the app will help them identify the colors in the photo.
If you have any additional questions on color blindness or want to discuss options, please contact Compton Eye Associates.