To Your Health: Many shades of color blindness

By Dr. Dan Coden, Scripps Health

Imagine being unable to tell the difference between a red car and a green one. Or hearing people rave about a “green flash” at sunset and seeing only brown.

People who have color blindness may be familiar with these scenarios. Color blindness is the inability to see certain colors the way everybody else sees them. It is caused by a problem with the color-sensing granules, known as pigments, found in the cones in the eye. The cones are nerve cells in the retina, which is the tissue that lines the back of the eye. The retina acts like a camera, converting the images that come through the eye into electric signals and sending them to the brain.

Most people have three types of cone cells; each type senses red, green or blue light. The amount of each color your cones sense determine what colors you will “see.” Depending on which cones they may be missing or how the cones are affected, people with color blindness may have difficulty seeing one of the three basic colors; for example, they can see blue and yellow but can’t distinguish between red and green. Others may see all three but be unable to tell the difference between shades of one color, or between similar colors such as light green and gray. Even if they can see many colors, people with color blindness may see them differently than most people. Often, the differences are so subtle that they may not even know they have the condition.

This type of color blindness is usually inherited and is much more common in men than women; about one in 10 men have some difficulty seeing color. In some cases, color blindness is caused by other factors not related to genetics, including aging, injuries to the eye, and eye problems such as cataracts or glaucoma. Some medications may also cause color blindness.

In rare cases, people see no color at all — only black, white, and gray. This is known as achromatopsia and may be associated with other conditions such as severe light sensitivity and very poor vision.

An ophthalmologist or optometrist can diagnose color blindness through several tests that measure your ability to recognize and distinguish between different colors. One such test determines how well you can see a pattern, such as a letter, number or shape, against a background of multi-colored dots. Depending on which patterns you can or cannot see, your doctor can diagnose your color perception abilities. Another test may ask you to arrange colored chips in similar groups.

It is important to diagnose color blindness as early as possible, since the inability to see some colors can interfere with activities such as driving, shopping or reading a computer screen. Certain careers that require acute color vision, such as a graphic designer, may not be options for people with color blindness. Children, especially, may have difficulty in school if their teachers are not aware of the problem; for instance, they may not be able to see certain shades of chalk or marker, or have trouble identifying colors. A professional vision screening is recommended for all children before entering school, ideally between the ages of 3 and 4.

Color blindness that is caused by medications or eye problems such as cataracts may be treatable in some cases; there is no treatment available for inherited color blindness. However, glasses that block glare often help color-blind people distinguish colors better, and colored contact lenses may help in some cases. Most people are easily able to compensate by using other visual cues such as where an object is located or what colors surround it.