The alternate use of both eyes occurs in cases where both eyes have good vision and both eyes can focus on the target, so the two eyes can be used alternately. The following foods have a protective effect on the eyes The following foods have a protective effect on the eyes and are recommended for patients who use both eyes alternately. 1. colorful fruits and vegetables – vitamin A “The night has given me black eyes, but I use them to find light.” But if the body lacks vitamin A, “looking for light” is much harder. Night blindness, as it is known, is caused by a lack of vitamin A in the body. Colorful fruits and vegetables, such as carrots, sweet potatoes, mangoes and papayas, are rich in beta-carotene, which can be converted into vitamin A in the body. Animal offal and cheese, eggs, fish, milk and yogurt are also sources of vitamin A. Recommended dosage: The recommended daily intake is 0.8 mg of vitamin A. A medium-sized carrot provides 0.4 mg; a large sweet potato provides about 0.2 mg. In addition, zeaxanthin is the main pigment in the macular region of the human eye, and orange and red peppers are an important source of zeaxanthin. 2, green vegetables – lutein Green vegetables are rich in lutein, and lutein can absorb harmful blue light and ultraviolet light, the eye’s lens and retina to play a protective role. Of the various green vegetables, kale has the most lutein, with about 11.4 mg per 100 grams. Although oranges and eggs also contain lutein, it takes enough oranges or 71 eggs to equal the amount of lutein in 80 grams of kale. Spinach is another good source, containing 7.9 mg of lutein per 100 grams. Recommended dosage: 10 mg of lutein per day, which means that eating one kale is enough. 3, shellfish and melon seeds – zinc Zinc is an essential element for human health and can enhance the sensitivity of the visual nerve. Lean meats, cereals, oysters, crabs, seeds and sardines are all important sources of zinc, with oysters containing the highest amount of zinc. Recommended dosage: 10 mg daily. 120 grams of sardines contain 2.6 mg of zinc, and a whole grain breakfast provides about 0.7 grams. 4, blueberries and blackberries – to protect the retina The pigments in blueberries and blackberries can protect retinal cells from aging and light-induced damage. Studies have also shown that the pigments in them can slow age-related macular degeneration and cataracts, but more research is needed. Recommended dosage: About two handfuls of blueberries or four spoonfuls of blackberries a day will do. 5, oily fish – Omega-3 fatty acids are high in the retina and can maintain the normal function of photosensitive cells. In addition, it can also lower cholesterol and promote cardiovascular health. Recommended dosage: Eat salmon, tuna and other oily fish at least once a week.