Do You Have Color Blindness?

One test that is often performed during the preliminary part of an eye examination is color vision assessment. This often is done by asking a patient to distinguish a number from a background of colored dots.

Color vision deficits are usually acquired genetically and are there for life, but sometimes they can be acquired later in life from other conditions. This article will introduce some of the types of color vision deficiencies.

What Causes Color Blindness?

At the back of the eye, the retina, there are special cells called rods and cones that absorb light and transmit signals to the brain.

Rods are great for detecting faint lights and peripheral motion, especially in the dark. Cones are responsible for detail and color vision and there are three different types for different colors: red, green, and blue.

The varying degrees that these different cones respond to light determine what color is perceived. For example, red is perceived if the red cone responds alone and orange is perceived if the red cone responds along with slight response from the green cone.

The relative responses of these cones depend on the wavelength of the light rays contacting the retina and being absorbed.

In color vision deficits, the complete lack of a type of cone or the decrease in numbers or response of a cone type will affect the color perceived.

A single cone type can be missing or reduced or, rarely, all cones can be missing due to a genetic defect, leading to very poor vision with no color detection whatsoever. This is the only instance where one is actually color “blind.”

With all other color vision issues, it is a problem with telling colors apart, not complete blindness to color.

Red Green Color Blind Defects

Patients with red-green color deficiencies often confuse reds with greens. This results from completely missing the cone for red colors (called protanopia) or green colors (deuteranopia), or by having all cone types with one of these cones having an altered spectrum of light that it responds to (protanomalous or deuteranomalous color vision).

This can manifest in varying degrees from having slight difficulty telling these colors apart to being completely unable to differentiate them.

This type of color vision deficiency is usually genetic and the individual will be born with it. Because of how the genetics work, it is often males that are affected while females are unaffected carriers of the responsible gene.

Certain diseases can also cause an altered perception of these colors such as swelling of the optic nerve at the back of the eye.

Blue Yellow Color Blindness Defects

This type of color vision defect is most often acquired later on in life due to chronic use of certain medications, cataracts, glaucoma, etc.

Although it can also be genetic, it is much rarer than red-green color deficiency. These patients experience difficulty discerning blues from yellows. Similar to red-green color deficiency, the degree of difficulty can vary.

Often, a color vision defect may not be a concern. Depending on the degree of the color deficiency, many people are not even aware of it until they are tested for it, though they may suspect it based on family history.

There are certain occupations that require one to be tested for color vision deficits, such as pilots, police officers, military, etc., because colored warning, signal, button lights need to be distinguished apart.

A color vision deficit may also affect career performance in areas where fine color discrimination is important, such as visual arts or interior design. However, there are many areas where color vision will not impact any part of job performance.

There are, for example, many eye doctors out there with varying levels of color vision deficiencies.