Poor color vision

DEFINITION

Poor color vision is a reduced ability to distinguish between certain colors. Although many people use the term “colorblind” to refer to the reduced ability to discriminate between colors, true colorblindness is a total lack of color vision, which is rare.

Poor color vision is usually inherited. Men are more likely to be born with poor color vision. Most people with poor color vision can’t distinguish between certain shades of red and green. Less commonly, people with poor color vision can’t distinguish between shades of blue and yellow.

Certain eye diseases and some medications also can cause poor color vision.

CAUSES

Seeing colors across the light spectrum begins with your eyes’ ability to distinguish the primary colors red, blue and green.

Light enters your eye through the cornea and passes through the lens and transparent, jelly-like tissue in your eye (vitreous body) to color-sensitive cells (cones) at the back of your eye in the retina. Chemicals in the cones distinguish colors and send that information through your optic nerve to your brain.

If your eyes are normal, you can distinguish different colors, but if your cones lack one or more light-sensitive chemicals, you may see only two of the primary colors.

Poor color vision has several causes:

• Inherited disorder. Inherited poor color vision is much more common in males than in females. The most common color deficiency is red-green, with blue-yellow deficiency being much less common.

  You can inherit a mild, moderate or severe degree of the disorder. Inherited poor color vision usually affects both eyes, and the severity doesn’t change over your lifetime.

• Diseases. Some conditions that can cause color deficits are diabetes, glaucoma, macular degeneration, Alzheimer’s disease, Parkinson’s disease, chronic alcoholism, leukemia and sickle cell anemia. One eye may be more affected than the other, and the color deficit may get better if the underlying disease can be treated.
• Certain medications. Some medications can alter color vision, such as some drugs that treat heart problems, high blood pressure, erectile dysfunction, infections, nervous disorders and psychological problems.
• Aging. Your ability to see colors deteriorates slowly as you age.
• Chemicals. Exposure to some chemicals in the workplace, such as carbon disulfide and fertilizers, may cause loss of color vision.

SYMPTOMS

You may have poor color vision and not know it. Some people figure out that they or their child has the condition when it causes confusion — such as when there are problems differentiating the colors in a traffic light or interpreting color-coded learning materials.

People affected by poor color vision may not be able to distinguish:

• Different shades of red and green
• Different shades of blue and yellow
• Any colors

The most common color deficiency is an inability to see some shades of red and green. Often, a person who is red-green or blue-yellow deficient isn’t completely insensitive to both colors. Defects can be mild, moderate or severe.

When to see a doctor

If you suspect you have problems distinguishing certain colors, see an eye doctor for testing. It’s important that children get comprehensive eye exams, including color vision testing, before starting school.

There’s no cure for inherited poor color vision, but if illness or eye injury is the cause, treatment may improve color vision.