Eye Health 27821

Eye Health

by Susan Colebank

As people age, they become more at risk for certain conditionsheart disease, cancer and bone ailments are just a few. The possibility of contracting any of these health problems strikes fear into Americans hearts. Results from a recent Harris Poll indicated cancer is still Americans greatest health concern. However, next on the list was not heart disease or bone issuesit was the fear of vision loss. Those most at risk for vision loss are the aging baby boomers (aged 40 and over), a group that was 119 million strong as of the 2000 U.S. Census.

Sight is both a simple and a complex process. Focusing the eye involves tears, the cornea, the pupil and the lens. Tears on the corneal surface are the first thing light touches when it greets the eye. The cornea, the main lens of the eye, focuses light; the corneal curvature determines the power of that focus. Light then passes through the pupil and meets up with the lens, where it goes through a clear jelly known as the vitreous. It is at the retina, a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface, that the art of seeing becomes a little more complicated.

Millions of photoreceptor cells cover the retina, absorbing light and turning it into nerve impulses. These nerve impulses travel the surface of the retina, meeting at the optic nerve. This nerve, which consists of approximately 1 million fibers, transmits information from the retina to the brain, which in turn gels the information into the image being seen.

The macula, a section of the retina, distinguishes fine detail and colors while the peripheral retina, which makes up the rest of the retina, distinguishes light from dark and gives a person peripheral vision.

It is not until sight is compromised that most people even notice the eyes workings. Loss of vision occurs in four prevalent ways: age-related macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma.

AMD is the most common cause of blindness and vision impairment for Americans aged 60 and older. Approximately 15 million Americans have AMD, according to The Macular Degeneration Partnership. This conditionwhich comes in dry and wet formsprimarily affects the region of the retina that oversees sharp central vision.

Dry AMD affects 90 percent of those with the disease; its cause is unknown. This condition begins when light sensitive cells in the macula break down. With less of the macula working, central vision may be lost in the affected eye. Dry AMD often occurs in just one eye at first. Wet AMD affects only 10 percent of AMD sufferers but accounts for 90 percent of all severe vision loss from AMD. It occurs when new blood vessels behind the retina start to grow toward the macula. Because these new blood vessels tend to be very fragile, they often leak blood and fluid. This causes rapid damage to the macula and can lead to the loss of central vision in a short period of time.

Cataract is another condition linked to vision loss, and this chronic disease has 20.5 million American sufferers aged 65 and older, according to the National Eye Institute (NEI). Cataract is characterized by a clouding of the eyes lens. As with most eye problems, increasing age contributes to cataract risk, but so do smoking, diabetes and excessive sunlight exposure.

Diabetic retinopathy impacts more than half of all diabetics, or approximately 5.3 million Americans aged 18 and over, due to both conditions affecting a persons vascular system. Retinal blood vessels break down, leak or become blocked, affecting and impairing vision over time. According to NEI, this condition is believed to be a leading cause of blindness in people ages 25 to 74.

Glaucoma, on the other hand, causes gradual damage to the optic nerve. When significant nerve damage is done, vision loss may occur. Approximately 2.2 million Americans 40 and older have been diagnosed with glaucoma, although another 2 million do not know they have it.

According to NEI, half of all cases of blindness can be prevented. Even Tommy G. Thompson, secretary of Health and Human Services, reported prevention is key in stymieing vision loss. Blindness and visual impairment from most eye diseases and disorders can be reduced with early detection and treatment, he said in a 2002 NEI release.

Is the American public receptive to this proactive thinking? The Natural Marketing Institute reported in its Health and Wellness Trends Database 46 percent of the general population would use supplements to treat vision problems, and 44 percent said they would use them to prevent vision problems.

Vitamins & Minerals

As with most of the nutrients making an impact on eye health, vitamins and minerals exert antioxidant effects that are the driving force behind their efficacy. Some of the most well-known research on antioxidants and eye health may be the Age-Related Eye Disease Study (AREDS), results of which were released in 2001.1 In the study on AMD, 3,600 participants were followed for 6.3 years, during which time a combination of vitamin C (500 mg/d), vitamin E (400 IU/d), beta-carotene (15 mg/d), zinc (80 mg/d) and copper (2 mg/d) was found to have a statistically better chance of stopping the progression of AMD compared to placebo. But even though the study showed promising results, Americans may not be taking the advice to heart. In a follow-up of AREDS, researchers polled 108 AMD sufferers from the study to see if they were still taking the supplements.2 Of the 79 percent still taking supplements, the mean doses of beta-carotene, zinc, and vitamins C and E were below AREDS recommendations.

Whether in combination or by themselves, antioxidants pack quite a punch in keeping eye diseases at bay. In a study of 500 non-diabetic women with cataracts, vitamin C was found to have a significant inverse relationship with nuclear opacitiesa cataract factor.3 Researchers under the U.S. Department of Agriculture (USDA) reported vitamin C, vitamin E or a multivitamin decreased the prevalence of nuclear opacities, and the prevalence was even lower in women who had taken vitamin C for 10 years or more. Vitamin C has also been seen to aid in glaucoma treatment by lowering intraocular pressure, a symptom in some glaucoma patients.4

Cataract formation is contingent on the eyes exposure to light, ultraviolet (UV) radiation in particular. In a lab animal experiment, rats deficient in vitamin E and zinc were exposed to UV-A and UV-B radiation; in the researchers investigation, they found the deficiencies enhanced UV radiation damage done to the cornea and lens of the deficient rats.5

An ingredient such as copper-zinc superoxide dismutase (CuZn-SOD) may also be of benefit in cataract health. In an in vitro model, CuZn-SOD scavenged free radicals in the lens and showed a possible protective role against cataract formation, according to Swedish researchers.6

Results from Italian research indicated short-term antioxidant therapy in the form of nutrients such as 20 mg/d of vitamin E and 18 mg/d of nicotinamide (a form of vitamin B3) may influence macular function in early age-related maculopathy (ARM), another macular degenerative disease.7 Then again, Australian researchers from the Blue Mountains Study reported early-onset ARM was not prevented with antioxidant or zinc intake during a five-year incidence follow-up.8

Vitamin E by itself may not reduce AMD risk.9 In research out of Australia and as part of the Vitamin E, Cataract and Age-related Maculopathy Trial (VECAT), 1,200 healthy volunteers, aged 55 to 80, were assigned to either 500 IU/d of vitamin E or placebo for four years. The incidence of early AMD was not significantly different: 8.6 percent in the vitamin E group versus 8.1 percent in the placebo group.

On a more promising note, vitamins C and E, in addition to selenium and alpha lipoic acid (ALA), a vitamin-like coenzyme, increase the bodys store of the antioxidant glutathione, deficient levels of which contribute to a poorly working antioxidant defense system in the eyes lens.10 ALA has been shown to exert antioxidant properties and regenerate other antioxidants in the lens cells.11

Oxidative stress seems to be a contributing factor in diabetic retinal alterations; therefore, it has been suggested that antioxidants may be beneficial in reducing diabetic retinal changes, researchers from Rome wrote.12 They studied the effects of vitamin E (200 IU/d or 500 IU/d) and selenium (8 mg/kg/d) on biochemical retinal changes induced by diabetes at different stages of the disease. They found four months of the combo reduced biochemical retinal alterations in diabetic rats with poor metabolic control.

More may be better in terms of antioxidants and reducing retinopathy risk. In diabetic rats, one of two regimens was given: vitamins C and E, or a mixture of vitamins C and E, beta-carotene, N-acetyl cysteine and selenium.13 Diabetic rats consuming the vitamins-only regimen experienced a 50-percent reduction in vascular lesions, and the ones on the antioxidant cocktail had an even more significant inhibition (55 percent to 65 percent). Thus, long-term administration of antioxidants can inhibit the development of the early stages of diabetic retinopathy, the Wayne State University authors wrote.

In a previous study conducted by the same researchers, the antioxidant cocktail appeared to help with reducing oxidative stress and nitric oxide, both of which may be inter-related with diabetes and diabetic retinopathy.14 Antioxidants such as vitamins C (1,000 mg/d) and E (400 IU/d) have also been seen to reduce oxidative damage created by nitric oxide in diabetics eyes.15

For overall eye health, combining vitamin A with zinc seems to be a winner. Researchers from Japan reported that based on a rat model, a synergistic interaction exists between vitamin A and zinc for maintaining corneal health.16 The vitamins precursorbetacarotene has shown dubious benefits for eyesight and was not shown to be good for smokers eyesight, in particular.17 It was found 50 mg every other day did not reduce cataract prevalence in 1,000 men in the treatment group, and smokers taking the vitamin had a higher risk of contracting cataracts.

Botanicals and Fats

One of the most well-known botanicals used for eye healthbut available through a prescription in a limited number of statesis marijuana. According to the National Academies, research since the 1970s has indicated the herb relieves intraocular pressure associated with glaucoma.

On the non-prescriptive, legal front, there are many other botanicals that help with various eye conditions. Researchers out of Japan reported grapeseed extract (GSE) may help with cataracts.18 Rats with hereditary cataracts were fed a standard diet containing 0-percent to .21-percent GSE (up to .08-percent procyanidins per day) for 27 days. GSE significantly prevented and postponed development of cataract formation by evaluation of slit lamp observations of the rats eyes. These results suggested that procyanidins and their antioxidative metabolites prevented the progression of cataract formation by their antioxidative metabolites, the studys authors wrote. The larger molecular procyanidins in the GSE might contribute this anticataract activity.

In research out of India, Ginkgo biloba was reported to help combat cataract formation via its antioxidant abilities.19 A standardized extract (EGb761) was used on rats in which cataract had been induced. Ginkgo was found to readily scavenge reactive oxygen and nitrogen radicals, inhibiting oxidative modifications that occur to proteins. It also entered intact cells and protected them against stress, and it prevented nuclear DNA from single strand breaks. In particular, the extract significantly retarded the progress of lens opacification in vivo.

In a human study conducted by German researchers, EGb761 also helped with AMD.20 Patients with impaired vision due to senile, dry macular degeneration were given either 240 mg/d or 60 mg/d of EGb761 for six months; after four weeks of treatment, all study participants vision was improved, with more pronounced improvements in the higher dose group.

In a paper out of Thomas Jefferson University, Philadelphia, researchers reported ginkgo and other Chinese herbal remedies that work on a vascular level may aid glaucoma sufferers.21 While ginkgo may not reduce intraocular pressure, research indicates it may improve blood flow to the optic nerve. Some glaucoma patients have normal intraocular pressure but poor circulation, resulting in damage to the optic nerve.22 Other glaucoma indicators ginkgo may be able to work on? Reduction of vasospasm, reduction of serum viscosity, platelet activating factor inhibitory activity and inhibition of apoptosis.23 Ginkgo may also have attributes that help sufferers of retinopathyresearchers in Argentina reported the herb worked as well as the anti-blood clot drug dipyridamole in benefiting retinal and vitreous tissues in retinopathy.24

Bilberry

(Vaccinium myrtillus), a botanical long-associated with improving night vision in pilots, may have a hand in reducing AMD risk. Researchers from Columbia University reported bilberry, along with vitamin E, quenched singlet oxygen responsible for factors leading to AMD.25 According to Milan-based Indena S.p.A., patients suffering from various diseases of the eye such as glaucoma and diabetic retinopathy benefited from the plants anthocyanosides effects on the retinal photoreceptors. In a study using Indenas Mirtoselect, a standardized bilberry fruit extract containing 36-percent anthocyanosides, the extract helped recover reduced visual function caused by overuse of the eyes, improving subjective symptoms such as vision with sparks, dimming of eyesight, and ocular fatigue in computer operators, office workers and students compared with patients treated with a placebo.26

According to research done for InterHealth USA in Benecia, Calif., makers of OptiBerry (a mixture of bilberry, blueberry, strawberry, cranberry, elderberry and raspberry extracts), berries, which are rich in anthocyanins, possess potent antioxidant, anti-aging and anti-diabetic properties. Anthocyanins also protect DNA integrity, provide cardiovascular protection, improved brain function and mental clarity, healthy vision, urinary tract health and dermal health, the studys authors wrote. Thus, the broad spectrum of current research supports the hypothesis that edible berries rich in anthocyanins provide a wide range of health benefits.27

Other botanicals have shown promise for cataract- and retinopathy-specific problems. For cataract health, green tea polyphenols may be the ticket.28 In a rat model, green tea was found to reduce the incidence of selenite cataract in vivo. And French maritime pine bark extract (as Hillside N.J.-based Natural Health Sciences Pycnogenol) may aid in diabetic retinopathy. Twenty patients with diabetes, atherosclerosis and other vascular diseases were given 150 mg/d for two months.29 Researchers found the extract benefited these patients, possibly by binding to blood vessel wall proteins and mucopolysaccharides and producing a capillary sealing effect, leading to a reduction in capillary permeability and edema formation. A research review out of Germany reported the same findings after investigating 1,300 cases in which Pycnogenol was used for retinopathy.30 They concluded the extract worked just as well as calcium dobesilate, a prescription drug used in retinopathy.

And whether sourced from plants or fish, essential fatty acids (EFAs) may also benefit eye health. In a study that included 350 patients aged 55 to 80, high intake of omega-3s was associated with a lower risk of AMD, as long as consumption of omega-6s (i.e., linoleic acid) was low.31 EFAs may be on par to vitamin E for enhancing phytodynamic therapy for AMD, too.32 In patients receiving either 200 mg/d of vitamin E or 1,000 mg/d of polyunsaturated fatty acids, visual acuity recovery time was significantly shorter in the two treatment groups after 20 days of supplementation compared to photodynamic therapy alone. The Italian researchers concluded retinal metabolic function improves with antioxidant therapy that includes vitamin E or fatty acids. And, the prevalence of late ARM increased in those aged 49 and older with the lowest intake of omega-3s.33

Daily Use of Eye Health Supplements
Source:The Health & Wellness Trends Database
The National marketing Institute, 2003

Carotenoids

Carotenoids may play a very important role in preventing blinding disorders such as AMD and cataract, according to researchers at the University of Maryland, College Park.34 Among 25 dietary carotenoids and nine metabolites routinely found in human serum, mainly lutein, zeaxanthin, lycopene and their metabolites were detected in ocular tissues, the studys authors wrote.

Lycopene

, for example, has been seen to help with diabetes-induced cataract, which is caused by osmotic stress coupled with a weakening in antioxidant defense mechanisms.35 Researchers in India reported lycopene increased glutathione and antioxidant enzymes in diabetic eyes.

However, the powerhouse carotenoids in eye health are the xanthophylls lutein and zeaxanthin. In its book Vision and Eye Health, the Mayo Clinic stated lutein and zeaxanthin are powerful combatants against the free radicals that cause eye problems. Researchers from Brown University hypothesized these carotenoids may improve visual function by reducing the effects of chromatic aberration, or by preferentially absorbing blue haze, a short-wave light that produces veiling luminance when viewing objects from a distance.36

Researchers out of The Netherlands reported lutein and zeaxanthin may have an inverse relationship with lens optical density and macular pigment optical density, suggesting the ingredients may retard lens aging.37 Increased risk of AMD may result from low levels of lutein and zeaxanthin in the diet, serum or retina, and excessive exposure to blue light, wrote researchers from Florida International University, Miami.38

However, zeaxanthin and lutein are not stored indefinitely in the body. Biochemical research has demonstrated that lutein and zeaxanthin, the two macular carotenoids, are bleachable pigments, wrote researchers from the University of New Hampshire, Durham.39 Further, evidence suggests that exposure to UV light can degrade plasma carotenoid levels in vivo.

According to Harvard researchers, retinal carotenoids such as lutein and zeaxanthin prevent photoreceptor cell death.40 From studies based on Japanese quail with retinal carotenoids that had been experimentally depleted through diet, the first evidence [was found] that retinal zeaxanthin protects photoreceptors from light-induced death, a factor in AMD. In further research by the same researchers, it was found that retinal zeaxanthin dose-dependently reduced light-induced photoreceptor apoptosis, even though increased serum levels did not, in another quail model.41

Lutein alone has been shown to improve visual performance, such as in cataract sufferers.42 Researchers gave 17 cataract patients-divided into three groups 15 mg of lutein (as 12 mg of all-trans-lutein and 3 mg of 13/15- cis-lutein present as mixed lutein esters, prepared as capsules by Quest International, a division of Unilever), 100 mg of vitamin E or placebo three times per week for up to two years. Serum levels of lutein and vitamin E increased, although statistical differences in improved visual acuity and glare sensitivity compared to baseline levels were only seen in the lutein group. Lutein supplementation may lead to a higher macular pigment density that could reduce the effects of chromatic aberration and increase glare sensitivity, the studys authors wrote. The improvement in visual performance of these patients with lutein supplementation may be related to acute and chronic effects in the retina and to the maintenance of the health and functional integrity of the retina and lens.

Luteins ability to improve macular pigment optical density is often credited for its effects. One study showed AMD patients taking a lutein supplement (as Des Moines, Iowa-based Kemin Foods FloraGLO Lutein) for 12 months at 10 mg/d, plus an antioxidant mixture, exhibited improved glare recovery, contrast sensitivity and visual acuity, in addition to improved macular pigment density compared to placebo.43

In research out of the University of Manchester, England, researchers compared the effects of lutein supplementation on macular pigment optical density in a group of ARM patients to controls.44 To begin with, ARM patients had lower macular pigment densities than controls, and 12 weeks of lutein supplementation (as La Grange, Ill.- based Cognis Xangold 15% Natural Lutein Esters) led to greater density in controls than ARM patients. However, affected ARM patients eyes respond equally to a lutein supplement, suggesting that, at least in the early state of ARM, the disease does not impede the deposition of lutein in the retina.

On the AMD front, astaxanthin also works as an antioxidant, preventing damage to the eye, according to Timothy Maher, Ph.D., who has received grants from Eustis, Fla.-based U.S. Nutra, the makers of astaZANTHIN. In research reported at Experimental Biology 2002, Maher and colleagues reported rats receiving astaZANTHIN experienced an attenuation in opacity formation, which indicated the supplement had potent antioxidant actions in the eyes lens.45

Supplementing the diet with various nutritional compounds may hold more promise than just good nutritionsupplementation may also lead to better eyesight at age 90 and beyond. Nutrition has a major influence on health, wrote Robert Abel Jr., M.D., in The Eye Care Revolution (Kensington Books, 1999). The American diet is generally unbalancedlow in many nutrients but high in saturated fats and simple sugars. The high level of saturated animal fats and refined carbohydrates has been implicated in the rise of chronic, non-infectious diseases. ... We dont go from well to ill in an instant, nor do we develop glaucoma, ulcers or heart failure overnight. Ill health usually results from a gradual deterioration. Such deterioration can often be reversedif we detect it early enough.

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