By Dr. Mercola
Color blindness is said to affect about one in 12 men and one in 200 women worldwide.1 However, most of these sufferers aren’t completely color blind, which is actually a condition called achromatopsia, and refers to people who can only see in black and white or shades of gray.
More common is “color vision deficiency,” which refers to the inability to distinguish between certain shades of color (usually shades of red and greens, but sometimes blues and yellows).
While people with normal vision can distinguish about 100 color hues, someone with color vision deficiency may only see 20.2 According to the American Optometric Association (AOA), “very few people are completely color blind.”3
How Do You See in Color?
Inside your eye’s retina are photoreceptors known as cones. The cones contain light-sensitive pigments that allow you to recognize color. Your eye’s cone recognizes red, green, and blue light based on light wavelengths. AOA continues:4
“Normally, the pigments inside the cones register differing colors and send that information through the optic nerve to the brain enabling you to distinguish countless shades of color.
But if the cones lack one or more light sensitive pigments, you will be unable to see one or more of the three primary colors thereby causing a deficiency in your color perception.
The most common form of color deficiency is red-green. This does not mean that people with this deficiency cannot see these colors at all; they simply have a harder time differentiating between them.
The difficulty they have in correctly identifying them depends on how dark or light the colors are.
Another form of color deficiency is blue-yellow. This is a rarer and more severe form of color vision loss than red-green since persons with blue-yellow deficiency frequently have red-green blindness too. In both cases, it is common for people with color vision deficiency to see neutral or gray areas where a particular color should appear.”
What Causes Color Vision Deficiency?
This condition is often inherited, passed from mother (who is typically a carrier of the gene but not color blind herself) to son, in which case it will occur in both eyes. Color vision deficiency caused by injury or illness, which is less common, may impact just one eye. Health conditions that may lead to color deficiency include:
Diabetes Glaucoma Macular degeneration Alzheimer’s disease Parkinson’s disease Multiple sclerosis Chronic alcoholism Leukemia Sickle cell anemia
Aging can also affect your ability to see colors vividly, as can certain medications, including those used to treat heart problems, high blood pressure, infections, nervous disorders, and psychological conditions.
Men Tend to Have a Harder Time Distinguishing Among Different Shades of Colors
It’s known that men and women tend to perceive colors differently, and one group of researchers suggested this could be due to the large number of testosterone receptors in the brain’s cerebral cortex.
Upon testing large groups of young adults with normal vision, they indeed found “marked sex differences in color vision.” Men, on average, were not as able as women to distinguish between shades of blues, greens, and yellows. They concluded:6
“We hypothesize that testosterone plays a major role, somehow leading to different connectivities for males and females: color appearance requires a re-combination and re-weighting of neuronal inputs from the LGN [thalamic neurons] to the cortex, which, as we show, depends on the sex of the participant.”
The Island of Color Blindness
The tiny Pacific island Pingelap is known as “Color Blind Island” because of its strikingly high number of people with the condition. In this case, many of the residents are truly color blind and able to see only in black and white. The condition affects about 10 percent of the island’s population.7
They describe challenges such as not being able to detect if food is “off.” Some of the inhabitants have other vision issues as well, such as having difficulty seeing in full sunlight (and seeing better at night). What caused color blindness to take over the island is related to a tsunami that occurred in 1780.
Only about 20 people were thought to have survived, including the king, who carried the genetic mutation for color blindness. Pingelap is a remote island with a relatively small gene pool, so the color-blindness gene has persisted for centuries.
Do You Have Color Vision Deficiency? Take This Test to Find Out
The Farnsworth-Munsell 100 hue test is one of the most well-known color blindness and color vision deficiency tests available. It involves sorting color plates by shade, which requires you to differentiate between colors and slight hue variations.
It consists of 88 color plates arranged in four batches of 22. They’re to be arranged so the colors appear to change gradually in steps. You can even take the test online.
If your color vision is normal, you’ll probably get a perfect score or make just a few errors. Those with color vision deficiency will have increasing numbers of errors depending on the severity of the deficiency.
It’s not a perfectly reliable way to diagnose color vision deficiency, especially given the variations that can occur due to computer monitor settings and ambient light conditions. However, it can give you an indication of where your color vision stands. If you have any doubts, visit an eye doctor to have your vision screened.
If You Have Color Vision Deficiency, Can It Be Cured?
While there is no known cure for this condition in its inherited form, color deficiency that’s the result of an underlying health condition may improve if the health condition improves. For those with inherited form color vision deficiency, tinted eyeglasses may be useful.
For instance, wearing glasses with a red tint may help you distinguish between different colors. Many people also learn to adapt around the deficiency by using labels (for clothing, for instance) and memorization.
For instance, to distinguish between the colors on a traffic light, people with color vision deficiency will memorize that the red light is on top, yellow in the middle, and green on the bottom.8
Want to Test the Quality of Your Eyesight?
Color vision is just one aspect of vision health. If you want to quickly test the quality of your eyesight, check out the video above. Researchers from the Massachusetts Institute of Technology (MIT) have created a hybrid image titled “Marilyn Einstein” to help you determine if you have good vision.
The picture combines a low spatial frequency (i.e. blurry) image of Marilyn Monroe with a high spatial frequency (i.e. clear) image of Albert Einstein. If your eyesight is working as it should, you should be able to see a detailed picture of Einstein when viewing the picture close up. As the image gets further away and/or smaller (or if you squint your eyes), the image of Monroe will appear.
It’s interesting to note that your perceptions of how well you’ll see Einstein may impact the way you actually see it. According to research by Harvard University psychologist Ellen Langer and colleagues, when people were primed to believe they had excellent eyesight, their vision improved.9
This could be an example of a placebo effect, but it could also be a manifestation of what happens when people relax and, as the researchers noted, adopt a mindset that vision will improve. This is actually the foundation of The Bates Method, which teaches you how to retrain your eyes to relax, thereby allowing you to see more clearly.
Are You Giving Your Eyes the Right Nutrients?
Your vision is precious, and while changes in diet won’t necessarily improve your color vision, especially if you struggle with inherited color vision deficiency, they will affect your eyesight overall (for good or for bad). For instance, high insulin levels from excess carbohydrates can disturb the delicate choreography that normally coordinates eyeball lengthening and lens growth. And if your eyeball grows too long, the lens can no longer flatten itself enough to focus a sharp image on your retina.
This theory is also consistent with observations that you’re more likely to develop myopia if you are overweight or have adult-onset diabetes, both of which involve elevated insulin levels. Following my nutrition plan will automatically reduce, or eliminate, excess sugar and grain intake from your diet while helping you optimize your insulin levels. Certain nutrients and foods, however, are also especially important for vision health. These include:
Dark Leafy Greens
The carotenoids lutein and zeaxanthin are primarily found in green leafy vegetables, with kale and spinach topping the list of lutein-rich foods. Lutein and zeaxanthin are both important nutrients for eye health,10 as both of them are found in high concentrations in your macula — the small central part of your retina responsible for detailed central vision. More specifically, lutein is also found in your macular pigment – known for helping to protect your central vision and aid in blue light absorption — and zeaxanthin is found in your retina.
According to one 1998 study in the British Journal of Ophthalmology orange pepper had the highest amount of zeaxanthin of the 33 fruits and vegetables tested.11 Zeaxanthin cannot be made by your body, so you must get it from your diet.
Organic Pastured Egg Yolks
Egg yolk is a source of both lutein and zeaxanthin along with healthy fat and protein, and while the total amount of carotenoids is lower than many vegetables, they’re in a highly absorbable, nearly ideal form. According to recent research,12 adding a couple of eggs to your salad can also increase the carotenoid absorption from the whole meal as much as ninefold. Keep in mind that once you heat egg yolks (or spinach) the lutein and zeaxanthin become damaged, and will not perform as well in protecting your vision; so cook your eggs as little as possible, such as poached, soft-boiled, or raw.
Wild-Caught Alaskan Salmon
Rich in omega-3s, the omega-3 fat DHA is concentrated in your eye's retina. It provides structural support to cell membranes that boost eye health and protect retinal function, and research suggests eating more foods rich in these fats may slow macular degeneration. In fact, those with the highest intake of animal-based omega-3 fats have a 60 percent lower risk of advanced macular degeneration compared to those who consume the least.13
A 2009 study also found that those with the highest consumption of omega-3 fats were 30 percent less likely to progress to the advanced form of the disease over a 12-year period,14 and a second study published in 2009 also found that those with diets high in omega-3 fats along with vitamin C, vitamin E, zinc, lutein, and zeaxanthin had a lower risk of macular degeneration.15
Wild-caught Alaskan salmon is a good source of astaxanthin, but you may not be able to eat enough of it to reap optimal clinical results. Astaxanthin is produced only by the microalgae Haematococcus pluvialis when its water supply dries up, forcing it to protect itself from ultraviolet radiation. Compelling evidence suggests this potent antioxidant may be among the most important nutrients for the prevention of blindness. It's a much more powerful antioxidant than both lutein and zeaxanthin and has been found to have protective benefits against a number of eye-related problems, including:
Cataracts Age-related macular degeneration (ARMD) Cystoid macular edema Diabetic retinopathy Glaucoma Inflammatory eye diseases (i.e., retinitis, iritis, keratitis, and scleritis) Retinal arterial occlusion Venous occlusion
Dr. Mark Tso,16 now of the Wilmer Eye Institute at Johns Hopkins University, but who was my boss when I worked at the University of Illinois Eye Bank in the1970s, has demonstrated that astaxanthin easily crosses into the tissues of your eye and exerts its effects safely and with more potency than any of the other carotenoids, without adverse reactions.
Depending on your individual situation, you may want to take an astaxanthin supplement. I recommend starting with 4 milligrams (mg) per day. Krill oil also contains high quality animal-based omega-3 fat in combination with naturally occurring astaxanthin, albeit at lower levels than what you’ll get from an astaxanthin supplement.
A diet rich in whole foods will be best for your vision health, while avoiding processed foods will help you avoid many risks to your eyesight. For instance, a diet high in trans fat appears to contribute to macular degeneration by interfering with omega-3 fats in your body. Even though its health risks are well known, trans fat is still found in many processed foods and baked goods, including margarine, shortening, fried foods like French fries, fried chicken, doughnuts, cookies, pastries, and crackers. You’ll also want to avoid artificial sweeteners, as vision problems are one of the many potential acute symptoms of aspartame poisoning.