The plant world offers a medley of prevention and treatment for healthy eyes.
Q. Are there herbs that can help support healthy eyes?
A. Sight is one of our most cherished senses. We read, appreciate art, observe nature and connect with loved ones by gazing into these “windows of the soul.” We spend good money on cosmetics to enhance the eyes’ natural beauty, and it just makes sense to promote our eyes’ health as well.
Easy steps include wearing sunglasses and hats outdoors, eating well, maintaining a healthy weight, managing stress and avoiding cigarette smoke. Some medicinal plants also might be worth incorporating into the routine.
Eyebright (Euphrasia officinalis) has long been a folk remedy for the eyes. Most natural food stores contain teas, tinctures and homeopathic eyedrops made from this herb. A South African study found that eyebright eyedrops hastened recovery from conjunctivitis (redness and discharge caused by irritation of the outside lining of the eye). Extracts lower blood sugar in diabetic rats. Whether the same effect holds for humans isn’t yet known. (Diabetes raises the risk for several eye diseases—see our sidebar "For Eye Health, Control Blood Sugar.")
Ginkgo (Ginkgo biloba) improves blood flow to the retina (the light-sensitive tissue at the back of the eye). Preliminary research suggests extracts improve vision in people with glaucoma. It is also antioxidant and protects nerve cells, including those in the eye.
Coleus (Coleus forskohlii) contains forskolin. Forskolin eyedrops have been shown to reduce the production of fluid within the eye, thereby reducing pressure. Therefore, it may have relevance in the treatment of glaucoma.
Cannabis (Cannabis sativa) contains cannabinoids, which, among many actions, reduce pressure within the eye in people with glaucoma. The first studies were done in people who smoked marijuana and showed that the pressure reduction lasted three to four hours. Subsequent studies have tried different methods to deliver cannabinoids (intravenously, oral or inhaled). The downsides are side effects (dry, pink eyes; reduced blood pressure; alterations in mental state and behavior) and legality (unless you live in a state that has legalized medical cannabis). However, the identification of receptors for cannabinoids in the eye has raised interest in the development of eyedrops.
Green tea (Camellia sinensis) contains antioxidants, which mop up free radicals—substances that create the so-called oxidative damage underlying many chronic diseases, including glaucoma, macular degeneration and cataracts. Furthermore, lab studies show that treating retinal cells with green tea’s polyphenols protects them from damage from ultraviolet light. (Such damage raises the risk for macular degeneration. UV light also contributes to cataracts.)
Bilberry (Vaccinium myrtillus) contains potent antioxidant flavonoids called anthocyanins. Its American botanical cousins blueberry and cranberry also contain such chemicals. During World War II, Royal Air Force pilots reported that eating bilberry jam improved their night vision. While initial studies supported such claims, more recent trials have not shown that bilberry benefits include a significant improvement in night vision. Most studies have used healthy volunteers with normal or above-average eyesight. Whether or not bilberry extracts might benefit elders with deteriorating night vision remains to be seen. One recent study did find that anthocyanins from another berry—black currant (Ribes nigrum)—hastened adaptation to the dark and also reduced eye fatigue.
Preliminary studies in humans from the 1980s suggested promise for managing cataracts, glaucoma and diabetic retinopathy. Studies in laboratory rats show extracts may defend against cataracts and glaucoma. In other studies, extracts protect nerve cells in the retina, strengthen blood vessels, improve circulation, and block the formation of new blood vessels, a process involved in diseases of the retina such as diabetic retinopathy and macular degeneration. Leaf and berry extracts also have an antidiabetic effect—a relevant action, given the high risk of eye diseases among diabetics.
Many herbs, fruits and vegetables have antioxidant power. Garlic (Allium sativum) is one. Preliminary lab research suggests it may help prevent cataracts. Turmeric (Curcuma longa) contains the potent antioxidant curcumin, which has been shown to protect against cataract formation in rats, both alone and in combination with vitamin E.
It’s important to note that most of the eye conditions discussed here come on so slowly that people may not develop noticeable symptoms until the disease has become severe. The best strategy is regular eye examinations. Early detection and prompt treatment can prevent significant visual loss.
Cataracts are so named because opacities in the eyes’ lens create the effect of looking through a waterfall (aka cataract). Risk factors include advancing age, diabetes, smoking, exposure to sunlight, excessive use of alcohol, poor nutrition, chronic stress and long-term use of corticosteroids.
In glaucoma, an imbalance in the production and drainage of the fluid within the eye builds pressure, compressing the optic nerve and causing tunnel vision and, eventually, blindness.
Macular degeneration affects a specialized part of the retina. Activities such as reading become steadily more difficult. Genetics play a role, but there are other risk factors, including advancing age, smoking, high blood pressure, obesity, inadequate nutrition and exposure to sunlight.
Diabetic retinopathy is a disease in which chronically elevated blood glucose levels damage the tiny blood vessels in the retina. Blood vessels may swell and leak. Also, new blood vessels can form. Both processes interfere with visual perception. High blood pressure also produces the disease.
Antioxidants quench free radicals, which cause oxidative damage throughout the body, including the eyes. Low levels of antioxidants correlate with an increased risk of cataracts, macular degeneration and possibly glaucoma; higher dietary intakes seem to protect against such age-associated eye diseases.
A large trial called the Age-Related Eye Disease Study found that supplementation with vitamins C (500 mg) and E (400 IU), beta-carotene (15 mg) and zinc (80 mg) for an average of six years significantly reduced the risk of progression to advanced macular degeneration.
Lutein and zeaxanthin are carotenoids that form the pigment for the macula, an area at the back of the eye key to visual acuity. Antioxidant and anti-inflammatory, they help filter out damaging blue light and ultraviolet light. Higher dietary intakes of lutein and zeaxanthin correlate with a reduced risk of cataracts and macular degeneration, and may also slow progression of the latter. Food sources include dark green leafy vegetables, guava, peas, broccoli, squash, carrots, yellow potatoes, corn, oranges and egg yolks. Nettles, dandelion, calendula, chrysanthemum and lamb’s quarters are herb sources.
Omega-3 fatty acids are anti-inflammatory, help maintain the fluidity of cell membranes and protect the retina from oxidative damage. Higher intakes of fish and fish oil (EPA and DHA) reduce the risk of macular degeneration and may even slow its course. Omega-3s may help reduce dry eye syndrome.
Elevated levels of glucose (sugar) damage proteins, generate free radicals and accelerate aging. Diabetes is the leading cause of blindness in the United States. People with this disease carry an increased risk of cataracts, macular degeneration, glaucoma and diabetic retinopathy. Even in people without diabetes, high-glycemic diets (those rich in simple carbohydrates, which rapidly increase blood glucose) have been linked to a heightened risk of macular degeneration and cataracts.
Linda B. White, M.D., co-author of The Herbal Drugstore, is visiting assistant professor in the Integrative Therapies Program at Metropolitan State College in Denver, where she teaches herbal medicine. The list of sources for this article is extensive. To receive a copy, please e-mail firstname.lastname@example.org, or write The Herb Companion, 1503 SW 42nd St., Topeka, KS 66609.
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