Healthy Eyes: The Basics
You can take several steps to protect healthy vision:
- Stop smoking. Smoking can increase one’s risk of developing cataracts, macular degeneration, and many other diseases by increasing oxidative stress, narrowing blood vessels, and reducing blood flow to the eye (Thornton 2005; Lindblad 2005).
- Wear a hat and sunglasses with ultraviolet (UV) protection whenever you are outdoors. The sun’s UV rays can increase the risk of developing skin cancer, cataracts, and macular degeneration (Xhauflaire 2005).
- Get regular, comprehensive eye examinations. Many eye diseases have no symptoms until late in the disease. Thus, many eye diseases are not apparent until diagnosed during a comprehensive eye examination. The American Academy of Ophthalmology currently recommends the schedule below for comprehensive medical eye examinations in healthy people with no family history, personal history, or risk factors for eye disease. Since everyone is different, consult your doctor as to how often you should get a comprehensive eye examination (American Academy of Ophthalmology 2000).
Age 20–29: at least once
Age 30–39: at least twice
Age 40–64: every 2–4 years
Age 65 or older: every 1–2 years
- Maintain a healthy diet and adequate nutritional intake. Your eyes rely on the nutrients you consume. This may be especially important in light of research implicating oxidative stress in major eye diseases. It is very important that all aging people maintain adequate antioxidant supplies to protect their eyes.
Some of the nutrients that benefit healthy vision work by directly supporting eye function, while others enhance blood flow to the eye by supporting the cardiovascular system. It is important that people with heart disease, such as coronary artery disease, visit their ophthalmologist and carefully follow their dietary program.
Omega-3 fatty acids. One group of dietary supplements that affects both the eye and the cardiovascular system is omega-3 fatty acids. These essential fatty acids help prevent hardening of the arteries in both the heart and the eye by reducing inflammation. Arteriosclerosis is a pervasive and quiet enemy of the eye. The result of arteriosclerosis is a decrease in nutrients to the eye and a reduction in the removal of waste products. An added benefit of omega-3 fatty acids is an apparent lower risk of dry eye syndrome, particularly in women (Miljanovic 2005).
Lipoic acid. Lipoic acid is a very powerful antioxidant that prevents free radical damage, thus reducing oxidative stress and possibly reducing the risk of degenerative eye disease. It has shown promise as a nutrient to protect rabbits’ eyes from ultraviolet damage (Demir 2005).
N-acetyl-L-carnosine. When administered topically, N-acetyl-L-carnosine can move easily into both the water-soluble and lipid-containing parts of the eye. Once there, it helps prevent DNA strand breaks induced by UV radiation and enhances DNA repair (Lou 2000). In the lipid areas of the eye, N-acetyl-L-carnosine partially breaks down and becomes L-carnosine. In a 1999 study of 96 patients aged 60 years or older with cataracts, one to two drops of a carnosine-containing solution was administered three to four times daily for three to six months. At the end of the study, the level of eyesight improved, and the lens became more transparent. For primary senile cataracts, the effective rate was 100 percent; for mature senile cataracts, the effective rate was 80 percent (Wang 2000).
Vitamin C. Intraocular pressure can be lowered by high doses of vitamin C. The osmotic changes are thought to impact either the outflow or secretion mechanism to reduce the pressure. Vitamin C may slow the progression of glaucoma (Head 2001; Bartlett 2004).
B vitamins. A decrease in B vitamins has been linked to heart disease. Because B vitamins are poorly stored by the human body, they must be ingested on a regular basis. Low levels of B vitamins, including vitamin B12, folic acid, and niacin, have been seen in glaucoma, diabetic retinopathy, and age-related macular degeneration (Head 2001).
While diabetes threatens whole-body health, the eyes are particularly vulnerable to damage. Damage to small blood vessels caused by diabetes can result in retinopathy (a disease of the eye’s retina, which collects visual information) and even blindness.
Scientists in Germany discovered that administration of benfotiamine (a fat-soluble form of vitamin B1) helped prevent retinopathy in test subjects with diabetes. Study subjects who received benfotiamine for 36 weeks demonstrated completely normalized levels of damaging advanced glycation end products (AGEs) in the retina, leading the research team to conclude that benfotiamine may help prevent or delay the onset and progression of diabetic retinopathy (Hammes 2003).
An exciting development in prevention of macular degeneration came from Harvard researchers (Christen 2009).
Using 5,205 women (40 years or older) known to have pre-existing cardiovascular disease or 3 or more cardiovascular risk factors (but who did not have macular degeneration at the start of the study), researchers conducted a large, randomized, placebo-controlled trial. Subjects were randomly assigned to receive either a combination of folic acid, pyridoxine (vitamin B6), and vitamin B12, or a placebo, and they were followed over an extended time period.
After an average of 7.3 years, researchers identified 55 cases of macular degeneration in the treatment group and 82 in the placebo group—this came out to a risk reduction of 34% in the vitamin supplemented group. That protection level rose to 41% for macular degeneration that was causing visual problems.
This was a truly stunning result, particularly since all subjects already had evidence of cardiovascular disease or increased risk, and the levels of supplementation were fairly modest—2.5 mg (2,500 mcg) daily of folate, 50 mg daily of B6, and 1 mg (1,000 mcg) daily of B12. Based on the study results, the author noted that “daily supplementation with folic acid, pyridoxine, and cyanocobalamin may reduce the risk of age-related macular degeneration.”
While further studies are needed to determine if B vitamins protect other populations against macular degeneration, this study provides hope that B vitamins may offer an accessible and low-cost preventive strategy against a leading cause of blindness in older adults.
Bilberry. Studies have shown the herb bilberry to be effective in vascular disorders. Bilberry contains flavonoids and antioxidants that increase microcirculation and support retinal function. This nutrient may be especially beneficial for individuals with macular degeneration, cataracts, diabetic retinopathy, and night blindness (Fursova 2005).
Many studies have demonstrated the superior and efficient antioxidant and free radical-scavenging activity of bilberry and other related berry fruits, along with genetic signaling abilities that favor their use in health promotion and disease prevention (Zafra-Stone 2007). Bilberry has also shown its strength in bolstering defense systems against harmful oxidative stress. In research involving tissue from the pigmented layer of the retina, bilberry proved a potent influence on beneficial gene pathways involved in the antioxidant response effort (Milbury 2007). In addition to a huge body of research showing bilberry’s benefits in vascular models of disease and atherosclerosis (Mauray 2010), bilberry has also shown its protective effects in other models of inflammatory eye diseases such as uveitis, with greater protection afforded by increasing extract dosage, or the so-called dose-response (Yao 2010).
French Maritime Bark extract. French maritime pine bark is a powerful antioxidant rich in proanthocyanidins, which are known for their ability to scavenge and neutralize harmful free radicals. The biologic effects of French maritime pine bark also extend to the natural agent’s abilities to help regulate the cell’s antioxidant network and associated genes, as well as dampen gene expression related to nuclear factor-kappaB (NF-kB)-dependent pathways inside cells, which have been shown to result in anti-inflammatory effects (Rohdewald 2002; Peng 2000).
Human studies have also shown the ability of French maritime pine bark to improve vascular endothelial function (Nishioka 2007), which involves the delicate layer of critical lining cells inside blood vessels that possess wide-ranging effects on vessel tone, integrity, inflammation, antioxidant protection, and repair. Disorders of endothelial function have also been cited as contributing factors to the development or progression of glaucoma (Resch 2009), which lends further support to the use of French maritime pine bark.
Interest in the benefits of French maritime pine bark grew with our understanding of the damage caused by free radicals. Mitochondrial-associated oxidative damage affects the eyes’ drainage system, whose tissue integrity is essential to maintaining normal eye fluid outflow and pressure (Izzotti 2010). This understanding of the role played by faulty mitochondrial function in the development of glaucoma pointed investigators toward possible dietary solutions.
Cyanidin-3-glucoside. Anthocyanins are pigmentary compounds that lend fruits like grapes, blueberries, and black currants their dark color.
Scientists are increasingly focusing on the benefits of one anthocyanin in particular: cyanidin-3-glucoside or C3G (Beckman 1998). Scores of studies in the past two years have established its potent combination of antioxidant, anti-inflammatory, DNA-protective, and gene-regulating effects.
C3G plays a unique role in protecting retinal tissue from damage. It works by multiple mechanisms at several sites in the retina. Most importantly, C3G stimulates regeneration of the retinal pigment rhodopsin (Matsumoto 2003). Rhodopsin is vital to vision in dim light. When depleted, rhodopsin takes longer to return to its normal, light-sensitive state. C3G increases restoration of rhodopsin levels (Tirupula 2009; Yanamala 2009).
C3G also serves to protect retinal cells against the harmful oxidation triggered by light (Jang 2005). It accomplishes this by reducing the accumulation of a fluorescent pigment called A2E that amasses with age and interferes with normal retinal function. C3G’s ability to quench oxygen free radicals is credited with this effect (Jang 2005).
Retinal cells are nerve cells capable of transmitting electrical signals. C3G and other cyanidin components of berries have neuroprotective effects on retinal cells (Matsunaga 2009).
- Beta-carotene. This carotenoid functions as an antioxidant by disabling free radicals. Low intake of beta-carotene is associated with increased free radical damage, which increases the risk of cataracts and macular degeneration (Mayne 1996).
- Zeaxanthin and lutein. Carotenoids are found in vegetables (red, yellow, green, and orange) and fruits. Carotenoids like zeaxanthin and lutein have highly antioxidative characteristics and help prevent destructive vascular changes in the macula, decreasing the risk of age-related macular degeneration. Studies indicate that high levels of lutein may decrease the incidence of posterior subcapsular cataracts, diminish complaints of glare, and provide better color vision and more critical acuity (Bone 2001).
- Meso-zeaxanthin. Meso-zeaxanthin, a nutritional cousin of lutein and zeaxanthin, is attracting attention for its application in eye health (Altern Med Rev 2005; Bone 2003; Bone 1993). Although not present in the typical diet, meso-zeaxanthin is produced from lutein in the retina (Altern Med Rev 2005; Bone 1993). Together with lutein and zeaxanthin, meso-zeaxanthin helps comprise macular pigment, the region of the eye’s retina that is crucial to detailed vision (Altern Med Rev 2005). Like many other biochemical processes, however, the conversion of lutein to meso-zeaxanthin is reduced by aging. A deficiency in meso-zeaxanthin can therefore result in a reduction in macular pigment density. Furthermore, a lack of ingested lutein or difficulty in synthesizing meso-zeaxanthin from lutein can further reduce levels.
A study showed that when individuals were supplemented with meso-zeaxanthin, their macular pigment density increased (Bone 2003). Since optimal macular pigment density is crucial to visual health, this suggests that supplementing with meso-zeaxanthin—in addition to consuming abundant lutein and zeaxanthin—may help fend off the onset of macular degeneration (Altern Med Rev 2005).
- Astaxanthin. Astaxanthin is a carotenoid xanthophyll, found naturally in the alga H. pluvialis, which gives lobster and other marine life consuming it a reddish hue.
In a double-blind study of 26 VDT workers (work requiring individuals to stare at a visual display terminal) randomly assigned to receive 5 mg astaxanthin or placebo daily for one month, those who received astaxanthin had a 54% reduction of eye fatigue complaints and objective improvements in accommodation ability (Nagaki 2002).
Only the astaxanthin group showed significant reduction of subjective symptoms. After four weeks of treatment with astaxanthin, the power of accommodation was significantly improved. On the other hand, placebo did not show any significant difference.
Research into the activity of astaxanthin has shown that its antioxidant mechanism may be complementary to that of vitamin E, which is also important in eye health and may help protect against age-related macular degeneration (Fletcher 2008). Free radical damage by UV light or other types of injury involves spreading of subatomic, negatively charged particles known as electrons. Astaxanthin is a chemical compound that can accept electrons easily, absorbing free radicals and stopping the chain reaction of tissue damage (Martinez 2008).
- Selenium. Selenium is an essential trace mineral with antioxidant properties that works in partnership with vitamin E to protect cellular integrity and cell membranes. It protects the cell membranes from free radical damage, decreasing the risk of macular degeneration, cataracts, and glaucoma. Numerous plants, including grains and garlic, contain selenium, but the concentration is highly dependent on soil content (Brown 1998).
- Taurine. High concentrations of taurine are needed within the eye to maintain optimal function and structure. It has been found to protect the lens against free radical damage (Mitton 1999; Killic 1999). In a series of studies performed by researchers at the University of Maryland (Mitton 1999), rat lenses were cultured with a potent oxidant called menadione. The addition of physiological amounts of taurine-enough to create a concentration roughly equivalent to that which would exist in healthy lenses-attenuated the harmful effects of the oxidant. Another study found that the lenses of diabetic rats were protected against cataract by physiological levels of taurine (Devamanoharan 1998).
- Coenyzme Q10. This nutrient has been studied in the context of age-related macular degeneration. In a randomized, double-blind, placebo-controlled trial examining the effects of coenzyme Q10 (CoQ10) combined with acetyl-L-carnitine and omega-3 fatty acids, researchers found that the nutrient mix improved and stabilized visual functions in patients with early age-related macular degeneration (Feher 2005). In an animal study, CoQ10 and vitamin E, applied topically, were found to help reduce the risk of complications after laser cornea surgery (Brancato 2002).
- Vitamin A. Vitamin A, retinol, and retinyl palmitate are multifunctional and essential in virtually all tissues. Vitamin A is required by the photoreceptors of the retina for proper function. Vitamin A, as an antioxidant, has been shown to decrease lipid levels in coronary heart disease; therefore, it may protect the ocular vascular system (Singhal 2001; Brown 1998).
- Zinc. This mineral is required to maintain the integrity of the immune system and of carbohydrate and protein metabolism. The retina has the highest concentration of zinc of any organ system (Grahn 2001). Previous studies suggest zinc may play a role in reducing the risk of age-related macular degeneration. However, other studies have presented a complex picture. At lower doses, zinc does have a protective effect against macular degeneration by supporting epithelial cells in the retina. However, at higher doses, zinc has the opposite effect (Wood 2003). Fortunately, this dangerous effect of zinc is attenuated by antioxidants, such as vitamin E, taken at the same time as zinc. Therefore, for anyone consuming zinc to help prevent age-related macular degeneration, antioxidants are recommended (Wood 2003).