More than half of all Americans will have or have had a cataract by the time they are 80 years old. Surgery is the only treatment when new glasses or brighter lighting no longer help you see better. But increasing your intake of vitamin C may help you to delay that surgery, or possibly avoid it completely.

Cataracts form when proteins in the eye begin to rearrange and clump together causing a small area of the lens of the eye to become cloudy. Over time, it becomes harder to see. Surgery removes the cloudy lens and replaces it with an artificial one.

Those people whose diets had plenty of vitamin C had a 20 percent lower risk for cataracts. Ten years later, those whose diets included more vitamin-C rich foods experienced a 33 percent lower risk of cataract progression.

Genetics is a risk factor for cataracts and many believed their development was inevitable. A new study suggests, however, that diet may trump genetics: you may be able to delay the development and slow the progression of cataracts with the food choices you make.

Researchers at King’s College, London, studied whether specific nutrients, either from food or supplements, could prevent the progression of cataracts once they formed, and how much environmental factors, like diet, mattered versus family history.

The research team collected information on the eating habits of 1,000 pairs of female twins to determine the women’s intake of vitamins A, B, C, D, E and the minerals copper, manganese and zinc. When the women were around the age of 60, digital imaging was used to determine the opacity of their lenses and measure the progression of cataracts. Ten years later, a follow-up measurement was performed on 324 pairs of twins.

At the baseline measurement, women whose diets were rich in vitamin C had a 20 percent lower risk for cataracts. Ten years later, those whose diets included more vitamin-C rich foods experienced a 33 percent lower risk of cataract progression.

The researchers found that 35 percent of the difference in cataract progression was attributable to genetic factors, while 65 percent was due to environmental factors, such as diet, making this the first study to suggest that genetic factors may not be as important in cataract progression as previously believed.

Vitamin C is a powerful antioxidant. High levels of vitamin C in fluid inside the eye help prevent the oxidation that causes the lens to cloud. Higher intakes of dietary vitamin C may increase the amount in the eye and provide extra protection against cataracts. Of note is the fact that the researchers’ findings apply only to dietary vitamin C, not vitamin C supplements.

Women need 75 milligrams of vitamin C a day, while men require 90 milligrams. People who smoke need an extra 35 milligrams per day.

Fruits and vegetables are the best way to get your vitamin C. Red and green peppers, oranges and orange juice, grapefruit and grapefruit juice, kiwi, broccoli, strawberries and Brussels sprouts are some of the best sources.

Five half-cup servings of fruits and vegetables a day should get you to your recommended intake — and perhaps put that eye surgery off for as long as possible.

The study is published in Ophthalmology.