Vitamin A also supports the function of the cornea, which is the protective outer layer of the eye. A person who is deficient in vitamin A may find that their eyes produce too little moisture to stay lubricated.

Beta carotene is the primary source of vitamin A in the human diet. Beta carotene is a type of plant pigment called a carotenoid that exists in many colorful fruits and vegetables. When a person consumes carotenoids, their body converts the pigments into vitamin A.

People can add vitamin A into their diet by eating the following foods:

Antioxidants help fight free radicals, which damage tissues throughout the body. Sometimes, free radicals may damage proteins within the eye. This damage can result in the development of cloudy areas — cataracts — on the lens of the eye.

A 2015 meta-analyses concluded that a high intake of vitamin E, whether through the diet or supplementation, may reduce the risk of developing cataracts.

Foods high in vitamin E include:

Vitamin C plays an important role in the eye itself, protecting against UV light damage. While the concentration of vitamin C in the eyes lessens with age, diet and supplementation can counteract this.

Vitamin C also helps protect against oxidative damage. Oxidative damage is a key factor in two of the most common age-related cataracts: cortical and nuclear cataracts. Cortical cataracts develop on the edges of the lens, while nuclear cataracts occur deep in their center.

A 10-year longitudinal study investigated different factors that may help prevent nuclear cataract development. The study involved more than 1,000 pairs of female twins. At the end of the study period, participants who consumed more vitamin C showed a 33% reduction in the risk of cataract progression. They also had clearer lenses overall.

However, a 2020 review concluded that more research is necessaryto fully identify the role of vitamin C as an anticataract therapy.

The following foods contain high levels of vitamin C:

A 2015 review found that people with tend to have lower blood B12 levels. However, researchers noted insufficient evidence to confirm a direct link.

However, this particular study only included women. Further research is, therefore, necessary to support the use of B-vitamins in preventing AMD in both males and females.

The following foods contain high levels of various B vitamins:

People who do not consume animal products can easily consume enough vitamin B12 through supplements and fortified foodstuffs.

Research suggests that the following nutrients are also beneficial for the eyes.

Lutein and zeaxanthin are carotenoids that exist in high quantities in green leafy vegetables. They are also present in the lens and retina of the eye.

As antioxidants, lutein and zeaxanthin may help reduce oxidative damage in the retina. Research in 2017 suggests that taking approximately 6 milligrams (mg) per day of lutein and zeaxanthin may lower a person’s risk of developing AMD. An intake of 0.5–1 mg per day may also lower the risk of glaucoma.

Sources of lutein and zeaxanthin include:

Zinc is a mineral that helps maintain the health of the retina, cell membranes, and protein structure of the eye.

Zinc allows vitamin A to travel from the liver to the retina to produce melanin. Melanin is a pigment that protects the eyes from UV light.

Zinc supplementation may help people who have AMD or are at risk of developing the condition. According to the American Optometric Association, taking 40–80 mg of zinc each day, alongside certain antioxidants, could slow the progression of advanced AMD by 25%. It could also reduce visual acuity loss by 19%.

Sources of zinc include:

The retina of the eye contains a high concentration of omega-3 fatty acids. These fatty acids help protect the retina from damage and degeneration. Small animal studies have found that omega-3 supplementation can slow age-related retina degradation. However, further human studies are necessary to fully assess the link.

Many doctors recommend omega-3 fatty acids for the treatment of dry eye syndrome. A person with dry eye syndrome does not produce enough tears to keep the eyes lubricated. However, a large randomized control study found no significant improvement in dry eye symptoms when compared to a placebo.

Foods rich in omega-3 fatty acids include:

However, some people may require additional supplementation to reach certain nutritional targets if their diet cannot provide this.

In some cases, taking supplements may lead to side effects, so it is important for people to speak with a doctor before making large dietary changes. For example, high dosages of zinc can affect how the body absorbs copper.