Are You Color Blind? How to Test for this Vision Deficiency
The retina of the eye has two types of light-sensitive cells called rods and cones, both found in a layer at the back of your eye that processes images. Rods work in low light conditions to help night visions while cones work in daylight to help color discrimination.
There are three types of cone cells and each type has a different sensitivity to light wavelengths. One perceives blue light, another perceives green and the third perceives red. Light enters your eye and stimulates the cone cells when you look at an object. Your brain interprets the signals from the cone cells to help you determine the color of the object. The red, green, and blue cones work together to create the color spectrum. For example, when the red and blue cones are stimulated in a certain way, you will see the color purple.
People with normal color vision have all three types of cone cells working correctly. On the other hand, color blindness occurs when one or more of the cone types are faulty. For example, if the green cone is faulty you won’t be able to see colors containing blue clearly.
What Causes Color Blindness?
Color blindness affects 1 in 12 men and 1 in 200 women in the world. Although this condition is primarily genetic, color blindness can result from other diseases such as diabetes and multiple sclerosis.
Red/green and blue color blindness is typically hereditary. The gene which is responsible for the condition is carried on the X chromosome, and is the primary reason why a much larger number of men are affected than women.
The effects of color vision deficiency can be mild, moderate or severe depending upon the defect.
What are the Types of Color Blindness?
There are several types of inherited color blindness. Here is an overview.
Trichromacy is normal color vision, which uses all three types of light cones correctly.
Anomalous Trichromacy uses all three cone types to perceive color, but one type of cone perceives light slightly out of alignment. As a result, different types of effects are produced depending on which cone type is faulty.
Protoanomaly reduces sensitivity to red light, deuteranomaly reduces sensitivity to green light, and tritanmaly reduces sensitivity to blue light and is extremely rare. The effects can range from almost normal range of color perception to almost total absence of perception of the faulty color.
Dicrhomacy has only two types of cones that are able to perceive color, with one completely faulty cone present. People suffering from protanopia are unable to perceive red light, those with deuteranopia are unable to perceive green light, and those with tritanopia are unable to perceive blue light.
Monochromacy, also known as achromatopsia, is the inability to see color at all. People with monochromatic vision perceive the world in different shades of grey, ranging from black to white. Achromatopsia is extremely rare.
How to Test for Color Blindness
Color blindness can be difficult to detect, particularly in children with inherited color vision deficiency. During a routine eye exam, your optometrist should test your color vision.
There are many tests available to measure color vision defects but the most common is the Ishihara Plate test. This tests for red/green color blindness, but not blue color blindness, and contains 38 plates of circles created by irregular colored dots in two or more colors. During the test, the plates will be placed in front of you and you will be asked what number you can see on the plate. Some plates may contain information which people with normal color vision can see while others may contain information that only people with color blindness can see. Your score will determine the diagnosis with color blindness.
For young children who are not old enough to identify numbers, a special plate test will be administered to test for color blindness.
More sophisticated tests are also available to diagnose whether someone with color vision deficiency would be suitable for certain occupations. A Lantern test is one such test, which is used to identify people not suitable to work as a train driver or in the marine and aviation industry where the responsibilities require the ability to accurately read colors of lights for safety reasons.
Regardless of the vision disorder you may be suffering from, we can help with a diagnosis and response plan to make managing your condition easier. Contact the team at Advanced Eye Medical today.