It is now proven that there is a link between good nutrition and the maintenance of healthy eyes. Many reports have indicated that some age-related eye diseases may be slowed by vitamins and minerals consumed in fruits and vegetables or taken as supplements.1
As we age, the importance of good nutrition increases for a number of reasons. The human body needs more vitamins and nutrients to keep it working properly, and it has a harder time digesting and processing the vitamins that we eat in our regular diets. Since the eyes are probably the most important organ connected to the senses, certain vitamins and nutrients can help protect the eye from age-related diseases such as age-related macular degeneration (ARMD).1,2
Vision problems, eye diseases, and other conditions can affect the physical health of the eye, and if the eye is not properly taken care of, blindness can result. Therefore, early detection and treatment of eye diseases can prevent vision loss. Annual eye examinations and good nutrition are very important to keep the eyes healthy. 1
The National Eye Institute (NEI) has reported that more than 9.3 million Americans have ARMD, one of the leading causes of vision loss for people aged >60 years. More than 23 million people have cataracts, and about 2.1 million have glaucoma. Diabetic retinopathy affects the vision of more than half of the 25.8 million people aged >18 years who have diabetes. This institution has ranked vision loss ahead of memory and hearing loss as measured by the number of people affected.1,3
Many causes of blindness are preventable through timely examination, good nutrition, and early treatment. In this article, we will discuss the role of certain vitamins and nutrients in maintaining eye health and in early eye treatment.
EYE PROBLEMS
Eye Diseases
Cataracts: Cataracts, or clouded lenses, affect vision and are very common in older people. Cataracts affect over 40% of people between ages 50 and 65 years, over 60% of people > age 66, and up to 90% of people >90 years. Common symptoms of cataracts include blurry vision, colors that seem faded, glare, poor night vision, double vision, and frequent changes in prescriptions for eyeglasses.1,2
The chance of developing cataracts can be greatly reduced by taking certain vitamins before the cataracts start to appear. However, in most cases surgery is an option that involves removing a cloudy lens and replacing it with an artificial lens.3
Glaucoma: Glaucoma damages the eye’s optic nerve and is an age-related eye disease that affects about 1 in every 200 people. The optic nerve damage is the result of increased intraocular pressure in and around the eye.2 Glaucoma has no early symptoms and usually goes undetected until it is fairly advanced. Loss of at least some vision is almost guaranteed if preventive measures are not taken and comprehensive eye examinations not done. Glaucoma is a leading cause of blindness among African Americans and Hispanics. African Americans experience this eye disease at a rate three times that of whites.2
Age-related macular degeneration: This disease affects about 9 million people in the United States alone. It is a disease that destroys the sharp central vision needed to see objects clearly. It affects all daily activities including reading, driving, and watching television. ARMD is a disease in which certain deposits or blood vessels under the macula can damage the eye rods and cause cells in the macula to die. In some cases, ARMD advances so slowly that people do not notice major vision problems.3
Diabetic retinopathy: Diabetic retinopathy is the result of diabetes and is another major age-related eye disease affecting the retina, the light-sensitive tissue at the back of the eye; it causes most cases of blindness in U.S. adults and is treated with surgery or laser surgery. With adequate control of blood glucose, blood pressure, and cholesterol levels, and with regular follow-up care, blindness from diabetes can be prevented.2
Vision Focus
Nearsightedness (myopia): Nearsightedness results in blurred vision when the visual image is focused in front of the retina, rather than directly on it. It usually occurs when the cornea or lens is not evenly and smoothly curved. For this reason, in children with nearsightedness light rays are not refracted properly. Nearsightedness often develops in the rapidly growing school-aged child or teenager and progresses during the growth years, requiring frequent changes in glasses or contact lenses.2
Farsightedness (hyperopia): Farsightedness results when the visual image is focused behind the retina rather than directly on it. Hyperopia may occur if the eyeball is too small or the focusing power is too weak. Farsightedness is frequently present from birth, but children can often tolerate moderate degrees of it without difficulty and most outgrow the condition.1,3
Astigmatism: In astigmatism, the cornea is more oval than round. This prevents the eye from allow focusing clearly. This condition is accompanied by near- and farsightedness. Current treatments adjust the cornea’s uneven curvature through corrective lenses or refractive surgery.3
Computer Vision Syndrome
Computer vision syndrome, or digital eyestrain, describes a problem that results from prolonged computer, tablet, e-reader, and cell phone use. Many people experience eye discomfort and vision problems when viewing digital screens for long periods of time. The level of discomfort appears to increase with the amount of digital screen use.
Uncorrected vision problems —farsightedness and astigmatism or eye-coordination difficulties—and aging can all contribute to the development of visual symptoms when using a computer or digital screen device. High visual demands of computer and digital screen viewing make many individuals susceptible to the development of vision-related symptoms.4
Solutions to digital screen–related vision problems are varied. In some cases, individuals who do not require the use of eyeglasses for other daily activities may benefit from lenses prescribed specifically for computer use. In addition, persons already wearing glasses may find their current prescription does not provide optimal vision for viewing a computer.
Many computer users experience problems with eye focusing or eye coordination that cannot be properly corrected with eyeglasses or contact lenses. A program of vision training may be needed to treat these specific problems. This program trains the eyes and brain to work together more effectively. These eye exercises help eye movement, eye focusing, and eye teaming and reinforce the eye-brain connection.4
Dry-Eye Syndrome
Dry-eye syndrome, also known as keratoconjunctivitis sicca, is an eye condition in which tear film evaporation is high or tear production is low. This will cause the eyes to dry out and become inflamed.5
The eyes are producing tears all the time, not just when people weep or have an emotional experience. Healthy eyes are covered with a liquid tear film, which is designed to remain stable between each blink. This tear film prevents the eyes from becoming dry and keeps them clear and comfortable. If the tear glands produce a lower quantity of tears, the tear film can become destabilized. It can break down quickly, creating dry spots on the surface of the eyes. Dry-eye syndrome is more common with older age, when the individual produces fewer tears, but it can occur at any age. In some parts of the world, where malnutrition results in vitamin A deficiency, dry-eye syndrome is much more common.
Symptoms of dry eye include stinging and burning sensations in the eyes, a feeling of dryness in the eyes, eye sensitivity to smoke, eye fatigue even after reading for a relatively short period, sensitivity to light, blurred vision, and sticking together of the eyelids upon waking up. Other complications are eye redness, painful eyes, and eyesight deterioration.
Artificial tears may be a simple, effective treatment for mild dry eyes. Eyedrops without preservatives can be used as many times a day as desired. Those with preservatives usually have a maximum safe dosage of four times a day. It may be a good idea to apply eyedrops before activities that may exacerbate dry eye symptoms. Ointments are generally better for nighttime use because they may blur vision. Eyedrops for removing redness should not be used.5
THE EYE AND NUTRITION
According to the CDC, fruits and vegetables of various colors help to promote optimal health. The National Eye Institute has reported that a combination of three antioxidant vitamins (C, E, and beta-carotene) and the minerals zinc and copper have reduced the advancement of ARMD by 25% and the risk of moderate vision loss by 19%. The results of a follow-up study indicated that adults who ate kale, mustard greens, collard greens, raw or cooked spinach (vegetables high in the pigments lutein and zeaxantine, called xanthophylls), and two antioxidants from beta (the carotene family) were at considerably less risk of developing advanced ARMD than those who did not eat them. Adults consuming more sources of the omega-3 fatty acids DHA and EPA were also at lower risk of this disease.1,6
Mechanism of Action
The yellow color of the macular region of the retina is due to the presence of macular pigment, composed of the two dietary compounds lutein and zeaxanthin, and a third, called meso-zeaxanthin. This compound is presumably formed from either lutein or zeaxanthin in the retina. The macular pigments absorb the blue light and protect the underlying photoreceptor cell layer from light damage. There is ample epidemiologic evidence that the amount of macular pigment is inversely associated with the incidence of ARMD, an irreversible process that is the major cause of blindness in the elderly. Either increasing the intake of foods that are rich in lutein and zeaxanthin or supplementing with lutein or zeaxanthin can increase the macular pigment in the retina. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of ARMD, more studies are needed to demonstrate this.1,7
Vitamin A
As mentioned, vitamin A has been known to have a beneficial effect in the eye as well as in the rest of the body. Vitamin A was the first vitamin studied in detail for its effects on the eye. The precursor beta-carotene (found in carrots and yellow or orange vegetables) is converted into forms of vitamin A called retinols. Retinols have numerous functions in the body, including assisting the bioelectrical process of vision (preventing loss of night vision), eliminating damaged cells from the body, and helping to prevent dry macular degeneration. Vitamin A palmitate (or retinyl palmitate, 5,000 IU) helps with day-to-day vision.8
Lutein is a carotenoid that is now thought to have more preventive properties than vitamin A at a dosage of 5 mg daily.2
Bilberry
As early as the 1940s, World War II pilots claimed that bilberries significantly increased their night vision when conducting night missions. Bilberries are smaller and of a darker blue color than blueberries. They are also softer and juicier than blueberries, making them difficult to transport. Because of these factors, bilberries are only available fresh in markets and are also more expensive. They are easily distinguished from blueberries because of the way they stain the hands, teeth, and tongue deep blue or purple. Bilberries contain natural antioxidants called anthocyanosides, which, among other properties, strengthen blood cells, significantly reducing hemorrhaging in the eye that can lead to both macular degeneration and diabetic retinopathy. Bilberries are also a good source of chromium, which helps control blood sugar levels and preserves the strength of smaller blood vessels—particularly important for patients with diabetes who are at risk for diabetic retinopathy.9
In addition, bilberries contain both vitamin A and vitamin C, which are vital to eye health. Recent studies have shown that bilberries also aid in stabilizing and preventing the deterioration of the collagen in eye tissue, thereby helping to prevent intraocular pressure issues such as occur in glaucoma. In Scandinavian countries, bilberries are collected from forests. They are eaten fresh or can be made into different jams, pies, and other dishes.9
Omega-3s and Other Vitamins
Omega-3s play an important role in eye health. DHA is naturally concentrated in the retina of the eye and is thought to promote healthy retinal function. It has been reported that eating larger amounts of fish or omega-3 may help promote macular health and reduce dry-eye syndrome.10
Both omega-3 and omega-6 essential fatty acids (EFAs) are the precursors of eicosanoids, locally acting hormones involved in mediating inflammatory processes. Recent studies have shown significant improvement in ocular irritation symptoms by the fatty acids linolenic and gammalinolenic acid administered orally. Evidence suggests that supplementation with omega-3 EFA may be beneficial in the treatment and prevention of dry-eye syndrome.11
Vitamin B2 (riboflavin) has also been used for years in helping to strengthen the cornea through a process called collagen cross-linking. Riboflavin has been shown to stop the onset of the eye disorder keratoconus.8 While vitamins can be obtained by taking supplements, it is best to get as many of these nutrients as possible through diet. A diet high in fruits and vegetables and low in trans fats and sugar not only helps with eye health but also contributes to overall health.
Although increasing the intake of antioxidants will probably not restore vision that is already lost, it may slow the progress of disease. Patients with eye problems should consult with their physicians about including more foods rich in antioxidants in their diet and/or taking vitamin supplements. Some people have other health considerations that could be affected by these dietary changes.
Nutrition and health are lifelong concerns, and people should not wait until they develop an eye problem or other health concern to make changes in their diet.
REFERENCES
1. Saljoughian M. Poor vision is not part of aging. US Pharm. 2012;37(9):HS-21-HS-24.
2. Demming-Adams B, Rixham CS, Adams WW III. McGraw-Hill Encyclopedia of Science and Technology. 11th ed. New York, NY: McGraw-Hill; 2012:549-555.
3. National Eye Institute www.nei.nih.gov. Accessed April 1, 2015.
4. American Optometric Association. Computer vision syndrome. www.aoa.org/patients-and-public/caring-for-your-vision/protecting-your-vision/computer-vision-syndrome. Accessed April 1, 2015.
5. Lemp MA. Management of dry eye. Am J Managed Care. 2008;14(4):S88-S101.
6. Bartlett H, Eperjesi F. A randomised controlled trial investigating the effect of lutein and antioxidant dietary supplementation on visual function in healthy eyes. Clin Nutr. 2008;27:218-227.
7. Krinsky NI, Landrum JT, Bones RA. Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye. Ann Rev Nutr. 2003;23:171-201.
8. Christen WG, Liu S, Glynn RJ, et al. Dietary carotenoids, vitamins C and E, and risk of cataract in women: a prospective study. Arch Ophthalmol. 2008;126:102-109.
9. Muth ER, Laurent JM, Jasper P. The effect of bilberry nutritional supplementation on night visual acuity and contrast sensitivity. Altern Med Rev. 2000;5(2):164-173.
10. Jang YP, Zhou J, Nakanishi K, et al. Anthocyanins protect against A2E photooxidation and membrane permeabilization in retinal pigment epithelial cells. Photochem Photobiol. 2005;81(3):529-536.
11. Seo T, Blaner WS, Deckebaum RJ. Omega-3 fatty acids: molecular approaches to optimal biological outcomes. Curr Opin Lipidol. 2005;16:11-18.
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