Eyesight

Do carrots improve your eyesight?

Carrots contain beta-carotene, which the body converts to vitamin A and needs for normal vision. If someone is severely vitamin-A deficient, correcting the deficiency can help. For a well-nourished person, eating piles of carrots does not create sharper vision or superhuman night sight.

The carrot story became famous during World War II, when Britain publicized the idea that carrots helped Royal Air Force pilots see at night. It was useful cover for the RAF’s improving airborne radar. Green leafy vegetables and other yellow, orange, or red vegetables also supply carotenoids.

The Blue Mountains Eye Study in Australia found that some people began eating more carrots after noticing night-vision trouble, so the diet change followed the symptom rather than preventing it. Later analyses produced mixed findings on antioxidants and age-related eye disease; cataracts and other age-related changes were more plausible explanations for the reported night blindness.

What do 20/40 and 20/200 mean?

Eye doctors established a standard for what a person with typical visual acuity can identify on an eye chart from 20 feet away. If you have 20/20 vision, you can read at 20 feet what the reference observer can read at 20 feet. In metric countries, the equivalent is 6/6 vision.

With 20/40 vision, you must stand 20 feet away to see detail that the reference observer can resolve at 40 feet. With 20/100 vision, you see at 20 feet what that observer sees at 100. In the United States, 20/200 is one part of the legal-blindness definition after best correction.

Vision can also be better than 20/20. A person with 20/10 vision sees at 20 feet what the reference observer sees at 10. The fractions describe distance acuity, not peripheral vision, color perception, depth perception, eye health, or every other part of seeing.

Hawks, owls, and other birds of prey pack a dense concentration of light-sensing cells into the retina. Some can resolve detail several times better than humans; a playful human-chart comparison puts a hawk at something like 20/2 vision.

Beta-carotene is not only in carrots

The Australian eye study noted that many participants who increased beta-carotene ate a narrow, carrot-heavy diet. Spinach and other dark leafy greens, sweet potatoes, pumpkin, squash, peppers, and many yellow, orange, or red vegetables provide carotenoids too.

A varied diet supports eye health, but age-related night-vision problems deserve an eye examination. Cataracts, retinal disease, glaucoma, medication effects, and uncorrected refractive errors cannot be fixed by treating carrots as medicine.