When you hear that someone is color blind, you may think it means a person can’t see colors at all, but it often means that someone can’t distinguish between certain colors. Color blindness occurs when you are unable to see colors in a normal way.

What is exactly is color blindness and what causes it?

In your eye’s retina (a thin layer of tissue that lines the back of your eye) there are two types of cells that detect light: rods and cones. Rods detect only light and dark and are very sensitive to low light levels. Cones detect color and are located near the center of your vision. There are three types of cones that see color: green, red and blue. Your brain uses input from cone cells to determine colors.

According to the American Academy of Ophthalmology, color blindness can happen when one or more of the color cone cells are absent, not working, or detect a different color than normal. Severe color blindness occurs when all three cone cells are absent. Mild color blindness happens when all three cone cells are present, but only one cone cell isn’t functioning correctly.

There are different degrees of color blindness. Some people with mild color deficiencies can see colors normally in good light, but have difficulty in dim, or low light. Others can’t distinguish certain colors in any light. The most severe and rare form of color blindness is referred to as achromatopsia, a condition in which everything is seen in shades of gray. Color blindness typically affects both eyes and is usually something that you have from birth, but it can also develop later in life.

What are the signs of color blindness?

Signs and symptoms of color blindness can vary. Many people have such mild symptoms that they are unaware they have a color deficiency. Parents may only notice a problem with a child when he or she is learning colors. Symptoms include trouble seeing colors and the brightness of colors in the usual way and the inability to tell the difference between shades of the same colors. This happens most often with red and green or blue and yellow. There are four types of red-green color blindness:

• Deuteranomaly is the most common type of red-green color blindness. It makes green look more red. This type is mild and doesn’t usually get in the way of normal activities.
• Protanomaly makes red look more green. This type is also mild and usually doesn’t get in the way of normal activities.
• Protanopia and deuteranopia both make you unable to tell the difference between red and green at all.

Blue-yellow color blindness is less-common and makes it hard to tell the difference between blue and green, and between yellow and red. There are two types of blue-yellow color blindness:

• Tritanomaly makes it hard to tell the difference between blue and green, and between yellow and red.
• Tritanopia makes you unable to tell the difference between blue and green, purple and red and yellow and pink. It also makes colors look less bright.

Am I at risk for color blindness?

The most common kinds of color blindness are genetic, meaning they’re passed down from parents. If your color blindness is genetic, your color vision will not get any better or worse over time. Men have a much higher risk than women for color blindness with 1 in 10 men having some form of color deficiency. You can also get color blindness later in life if you have a disease or injury that affects your eyes or brain including:

• Trauma
• Effects from drug use
• Metabolic disease
• Vascular disease
• Eye conditions such as glaucoma or macular degeneration

There’s no cure for color blindness that’s passed down in families, but most people find ways to live with it. Keep in mind that most of the time, color blindness doesn’t cause serious problems. If your color blindness is happening because of another health problem, your doctor will treat the condition that’s causing the problem. If you’re taking a medicine that causes color blindness, your doctor may adjust how much you take or suggest you switch to a different medicine. If color blindness is causing problems with everyday tasks, there are special contact lenses and glasses that may help people tell the difference between colors.

Your ophthalmologist can use a simple test, called a color plate test, to tell you if you’re color blind. During the test, your doctor will show you a circle made of many different colored dots. The circle has a shape inside it that’s made out of dots — like a number or letter. This shape is easy to see if you don’t have color blindness, but people who are color blind have a hard time seeing it.

It’s important to visit your optometrist or ophthalmologist for regular eye exams. Your doctor can help create a plan tailored to your condition or needs.