En español | It’s one of the most memorable scenes in movie history. In The Wizard of Oz, pigtailed farm girl Dorothy opens up the door to her farmhouse — which has come plummeting down to Oz, after a doozy of a tornado — and goes from a world of muted sepia tones to one of vibrant, glorious Technicolor. This legendary piece of Hollywood magic makes one thing clear: Color is a powerful thing.
People who are color-blind can’t appreciate the rainbow of hues that so many of us take for granted. But not being able to see all colors properly goes beyond mere aesthetics. It can make simple everyday tasks a challenge — from traveling (say, differentiating the colors in a traffic light or reading a subway map) to eating (being able to tell if a banana you’re about to peel is ripe) to getting dressed (color-coordinating can be a nightmare).
Color blindness is often misunderstood. One common misconception is that people who are color-blind live in a world devoid of color. “In fact, the vast majority of people who have color blindness can see colors, but certain colors — red and green, in particular — appear washed out and muddy,” says ophthalmologist Jane Edmond, director of the Mitchel & Shannon Wong Eye Institute and a professor in the Department of Ophthalmology at Dell Medical School, at the University of Texas at Austin. “This can make distinguishing between certain colors a challenge.”
In fact, says Edmond, “color deficiency” is a more accurate way to describe the condition.
Color blindness can range from mild (some people only have trouble distinguishing colors in dim light, for example) to more severe, but the degree of severity doesn’t change and usually doesn’t affect the sharpness of vision. Trouble seeing the difference between red and green (or red-green color blindness) is the most common form of the condition. Both colors may take on a kind of brownish murky-greenish tone, which can make for some confusion. “One of my patients, who is red-green color deficient, would pick wild strawberries as a young child,” says Edmond. “He would always come back with a basket of leaves, because he had a hard time distinguishing between red and green.”
An inability to distinguish between blue and yellow is much less common. Being completely color-blind (read: seeing things in black, white or shades of gray) is a severe form of the condition, called achromatopsia. It’s extremely rare and accompanied by bad overall vision.
How it happens
The retina is covered with two types of light-sensitive photoreceptors, called rods and cones. Rods detect light and dark. Cones are responsible for color vision. There are three types of cones: One perceives longer (or red) wavelengths, another medium (green) wavelengths, and another short (or blue) wavelengths. Together, these cones allow us to see an entire spectrum of colors. If just one type of cone is faulty, the eye may have trouble seeing certain hues. Reasons for that include:
Genetics. In most cases, people are born color-blind — men far more frequently, because the X chromosome, passed on from mother to son, carries the genetic information for color vision. (According to the American Optometric Association, nearly 8 percent of males and 0.5 percent of females are born with color deficiency.) Males, who have an X chromosome and a Y chromosome (XY), only need an abnormal X chromosome to become color-blind. A color-blind woman has two abnormal X chromosomes (XX), one each from her mother and father.
Age. Color vision can also worsen with age. This is known as acquired color blindness. Cataracts, in particular, can throw things out of whack. “As we age, our lens can turn cloudy, which decreases the amount of light getting to the retina,” explains Edmond. “Over time, the aging lens can turn a yellow or brown color, which leads to altered color perception — sort of like looking through glasses with yellow- or brown-tinted lenses.”
People with advanced lens discoloration may not be able to identify blues and purples properly, she notes. (Removing a cloudy natural lens and replacing it with an artificial lens can restore color vision.)
Injury or disease. Damage to the optic nerve, or to parts of the brain that process color, or diseases such as diabetes, multiple sclerosis, Parkinson’s disease, Alzheimer’s and stroke can cause color blindness. Unlike congenital color blindness, these types of color vision problems affect men and women equally, and one eye may be affected more than the other.
Medications. Certain drugs can play havoc with your ability to see hues as well. Possible culprits include antibiotics and drugs used to treat high blood pressure, heart conditions, erectile dysfunction and psychological disorders. If you’re downing an Rx, let your physician know about any color vision changes you may be experiencing.
How to know if you are color deficient
One of the most widely used tests, to detect red-green color deficiency, is the Ishihara Test. It’s composed of a series of plates, each containing a circle of hundreds of similarly colored dots (say, dark and light orange) in different sizes. Inside each circle of dots is the image of a number, which is made up of dots in a contrasting color (for example, light and dark green). In some cases, a person with normal color vision should be able to find the number in the circle of dots, while those who are color vision deficient cannot — or will see an entirely different number. And some plates are designed so the color-blind person sees a number that is hidden to those with normal color vision.
Another test for color vision loss: the Farnsworth D-15 (D15). The goal is to arrange the 15 colored discs, in a subset of colors (ranging from brown, green, blue, to purple), in a particular order, creating a row of graduated colors.
For a quick at-home screening, you can try either test online. But keep in mind that you may not be getting the most accurate reading. “The light source is important,” says Chris Johnson, a professor in the Department of Ophthalmology and Visual Sciences at the University of Iowa Institute of Vision Research. “Sometimes people will use normal room light or a desk lamp when taking a test and get a false response. For the most accurate reading, have it done by an ophthalmologist.”
Living with color deficiency
For those who do have a problem, there are some crafty ways to coexist with the condition — for example, labeling clothes to avoid unfortunate clashes of color or simply committing things to memory (such as that the red light is at the top in a traffic light).
Or you can turn to technology. Colored filters, available in contact lens or eyeglass lens form, can help, says Johnson, but “they don’t correct overall color vision, they just change it. It’s more about improving contrast, making it easier to distinguish between colors, and improving brightness so you can see colors more vividly.”
And these slip-ons don’t come cheap: EnChroma glasses, one of the most popular brands, will set you back a few hundred dollars. A less expensive way to work around the condition is to tap on an app. Touch a specific point in a picture and Color Blind Pal will offer the color name (say, teal blue). Visolve is a tool that uses filters to make specific colors in a camera photo or on a computer display lighter, darker or more vivid.