Aging, diabetes, oxidative damage and other challenges of life wield the potential to produce a host of debilitating ocular woes. However, supplementation with various antioxidant vitamins, minerals and carotenoids and botanicals may help prevent degenerative eye diseases such as age-related macular degeneration, cataracts, glaucoma and diabetic retinopathy.
Although taste, touch, smell and hearing contribute powerfully and uniquely to the richness of life, many would cite vision as the most prized of the five senses. Sight is the dominant means of perception among humans, with over 90 percent of data entering the brain through visual cues.1 Since perception is chiefly visual in nature, it is hardly surprising that Americans fear blindness more than other physical impairments.2
The human eye is an extraordinary organ. Its chief occupation is to focus light rays originating from a range of distances in a variety of lighting conditions. In the healthy eye, light is converted to impulses and transmitted to the brain where an image is perceived.
Much like the parts of a camera work to produce pictures, the structures comprising the eye play specialized roles in the process of sight. Similar to the aperture of a camera, the cornea bends rays of light through the pupil in the center of the colored iris. The light then enters the lens. Like the lens in a camera, the lens of the eye serves to focus light on the back of the eye. The retina—the membrane containing photoreceptor nerve cells at the back of the eye—functions like the film of a camera by converting the light rays into electrical impulses and sending them through the optic nerve to the brain where an image is perceived.
The center of the retina—the macula—is responsible for detailed, central vision, while the outer retina is responsible for peripheral vision. Excessive light reaching the retina can cause damage to the photoreceptor cells by overwhelming their metabolic systems.
As with a camera, if the film (i.e. the retina) is bad, the viewer will not obtain a good picture.
The prevalence of degenerative eye diseases is increasing in the United States and vision loss is becoming a major public health concern.3 Blindness or low vision affect 3.3 million Americans age 40 and over, or one in 28 individuals.4 By the year 2020, the number of Americans suffering from visual maladies is predicted to reach 5.5 million.5 Changing age demographics are to blame for this projected increase in vision loss. By age 65, 33 percent of Americans has some form of vision-impairing eye disease.6
Due to chronic symptoms including elevated blood sugar and pressure, diabetics are another group particularly prone to degenerative diseases of the eye. According to the American Academy of Ophthalmology, diabetics are 25 times more likely to lose vision than those who are non-diabetic.7
The chief degenerative maladies of the eye include age-related macular degeneration (AMD), cataracts, glaucoma and diabetic retinopathy. In general, oxidative damage is the primary cause of degenerative eye diseases. Like any other organ, the eye is susceptible to the effects of singlet oxygen and other free radical species.
AMD is a disease of the macula that causes blurriness, waviness or a blind spot in central vision. There are two types of AMD—wet and dry. In wet AMD, the more rare and serious of the two conditions, rogue blood vessels grow beneath the retina. These delicate capillaries rupture and leak, interfering with normal vision. In dry AMD—the more common form—the light-sensitive photoreceptor cells of the macula slowly degenerate, resulting in gradual loss of central vision.
Cataracts, which block the passage of light into the eye, are another byproduct of the aging process. These opaque obstructions—caused by the congealment of protein in the lens—appear as milky or yellowish areas in the pupil that cause the normally transparent lens to appear cloudy.
There are three types of cataracts: nuclear, cortical or subcapsular. A nuclear cataract develops in the center—or the nucleus—of the lens, while a cortical cataract begins to form around the border of the lens and converges in the nucleus as it grows. Cortical cataracts are especially prevalent among diabetics, and subcapsular cataracts develop at the back of the lens.
The progression of a cataract is difficult to detect as it may be inconspicuous at first. It may blur or cloud vision slightly, or uncomfortably intensify light from the sun, a lamp or oncoming headlights. Cataracts may also cause colors to appear duller than usual. Eventually, a lens adulterated by cataracts must be surgically replaced with an artificial substitute.
Glaucoma refers to a group of diseases that cause irreparable damage to the optic nerve. It occurs when the blood pressure in the eye increases beyond healthy limits, resulting in optic nerve damage and vision failure. Beginning with loss of peripheral vision, the symptoms of glaucoma advance so gradually that the patient often fails to realize the progression of deteriorating vision. Left untreated, glaucoma eventually leads to tunnel vision, followed by blindness.
Diabetic retinopathy occurs as a consequence of the elevated blood sugar of diabetes. It causes the blood vessels in the retina to weaken and leak blood, which leads to distorted or cloudy vision. As the damaged capillaries heal, scarring causes the retina to detach from the rear of the eye, leading to more serious vision loss or blindness. In proliferative retinopathy—the advanced stage of the ailment—new blood vessels form on the surface of the retina and bleed into the clear, jelly-like substance in the center of the eye (the vitreous).
One sign of diabetic retinopathy can be the appearance of floaters—specks or shadows in the field of vision. Another sign may be difficulty reading or seeing up close, which can indicate the presence of fluid in the macula, the most light-sensitive part of the retina. One more sign may be double vision, which occurs when the nerves controlling the eye muscles are affected.
A common trait of the major degenerative eye diseases is usually their painlessness. The absence of pain makes deterioration of the eye difficult to detect. By the time a patient realizes the need for treatment, it may be too late to undo the damage.
Some of the most pivotal research conducted on eye health is the Age-Related Eye Disease Study (AREDS), a series of scientific reports published in the Archives of Ophthalmology and funded by the National Eye Institute. In the eighth AREDS report, a randomized, placebo-controlled clinical trial conducted to determine what role micronutrients might play in the development and progression of cataracts and AMD, 3,640 men and women between the ages of 55 and 80 were administered various combinations of micronutrients and monitored for an average of 6.3 years. One of the conclusions drawn by the researchers was supplementation with vitamin C, vitamin E, zinc and beta-carotene might reduce the risk of degenerative diseases of the eye.8 These vitamin, mineral and carotenoid antioxidants may inhibit free radical formation, quench singlet oxygen and scavenge for free radical species, decreasing lipid peroxidation and preventing injury to the photoreceptor cells in the eye.
According to the eleventh AREDS report, if the 8 million Americans age 55 or older at high risk for developing AMD took supplements of antioxidants and zinc (a mineral antioxidant), an estimated 329,000 of them would avoid the disease, as well as any associated vision loss during the following five years.9 The researchers concluded if people at high risk of developing advanced AMD took the supplements as suggested by AREDS results, the potential impact on public health in the United States would be considerable between 2003 and 2008, and if no treatment were given to reduce their risk, an estimated 1.3 million people would develop advanced AMD.
Other compounds useful in the prevention of degenerative eye diseases are carotenoids— naturally occurring antioxidant compounds with the ability to selectively absorb light. Carotenoids are adept at quenching singlet molecular oxygen formed in photooxidative processes that may contribute to light-induced damage in the eyes.10
Lutein and zeaxanthin are the predominant carotenoids in the human macula. They form the yellow pigment of the retina and help process blue light, a harmful component of sunlight.
Several clinical trials suggest a positive correlation between supplemental lutein and reduction of AMD risk. “After 10 years of research and development, science has been able to establish a pretty good case that lutein may reduce risk of macular degeneration,” said Craig Maltby, communications manager with Des Moines, Iowa-based Kemin, which supplies FloraGLO®, a purified, GRAS (generally recognized as safe) extract derived from petals of marigold flowers containing zeaxanthin and crystalline lutein. “For people who either are at risk of AMD or who may have early or intermediate AMD symptoms, lutein in the diet appears to offer as good of a riskreduction agent as can be found,” he said.
According to a study conducted by researchers at Singapore Polytechnic, supplementation with lutein esters (as La Grange, Ill.-based Cognis Nutrition’s Xangold®; equivalent of 10 mg/day free lutein) increased macular pigment density and serum lutein levels in patients with early and late-stage AMD.
Another study, conducted at the Medical Center Eye Clinic, North Chicago, Ill., in which 90 patients with atrophic AMD received 10 mg lutein (as FloraGLO® from Des Moines, Iowa-based Kemin Foods); 10 mg of a broad spectrum antioxidants formula including lutein, vitamins and minerals; and a maltodextrin placebo over 12 months; found lutein or lutein together with a broad spectrum of antioxidants, vitamins, and minerals improved visual function in the treatment of AMD.11
In addition, a study published in the Journal of the Science of Food and Agriculture showed lutein ester supplements (also as FloraGLO) improved vision in patients with cataracts and AMD.12 Five patients with cataracts took lutein ester capsules three times weekly for 26 months, and five patients with AMD took lutein ester capsules three times weekly for 13 months.
Each capsule contained 15 mg lutein esters and 3.3 mg of vitamin E. Cataracts patients were monitored for visual acuity, glare sensitivity and contrast sensitivity, while AMD patients were tested for visual acuity.
Cataracts patients improved by 40 to 50 percent, and their ability to tolerate glare also improved. Meanwhile, the four patients with AMD who completed the study exhibited stabilized or improved vision. None of the patients experienced side effects, and all patients reported improved vision.
In another study reported in Investigative Ophthalmology & Visual Science, researchers used monkeys raised on a carotenoid-free diet and that showed no carotenoids in their plasma or the retina to demonstrate that supplementation with lutein and zeaxanthin (as Optisharp™, provided by Parsippany, N.J.-based DSM Nutritional Products) quickly increased plasma concentrations of lutein and zeaxanthin and macular pigment density.13 In addition, supplementation with lutein and zeaxanthin caused partial normalization of the distribution of the animals’ retinal pigment epithelium (RPE) cells.
Astaxanthin is another carotenoid thought to protect the human eye. The most abundant xanthophyll in the animal kingdom, it is the major pigment of crustaceans and used as a commercial colorant. According to Larry Line, vice president, international, with Cupertino, Calif.-based U.S. Nutra—which offers patented astaxanthin for the treatment of ocular and degenerative diseases (Zanthin™)—various studies have shown astaxanthin is as much as 1,000 times more effective than lutein or beta-carotene in protecting against UVA radiation. Astaxanthin is a powerful antioxidant that can measure between 50 and 550 times more potent than vitamin E; has dose-dependent ocular antiinflammatory effects through suppression of nitric oxide, prostaglandin E2 and tissue necrosis factor alpha; and readily crosses the blood-retinal brain barrier to concentrate in the retina of a mammal, Line said.
Line cited a study cited in U.S. Nutra’s Zanthin patent in which rats were subjected to a 12-hour cycle of light and darkness for 14 days, and administered 80 mg astaxanthin/kg/day delivered in soy bean oil or a placebo of isolated soy bean oil starting nine days prior to light exposure and continuing for 11 days. All of the rats were kept in the dark for a six-hour, six-day or 13-day recovery period, euthanized with an overdose of pentobarbital, and then examined for eye damage. Injury to photoreceptor cells was measured by the thickness of the outer nuclear layer of the retina. Levels of rhodopsin—a light-sensitive protein in the rods of the retina—were also measured, as a decrease in rhodopsin indicates damage to the retina. According to the results, rhodopsin levels in the control group fell for six days following photic injury then rose. In astaxanthin-treated rats, rhodopsin levels increased over six days then remained constant through the thirteenth day following photic injury. The researchers concluded astaxanthin not only protected the photoreceptor cells from photic injury but also ameliorated the effects of the photic injury since rhodopsin levels did not fall, but instead increased after photic injury.
Diets high in essential fatty acids (EFAs) are thought to be inversely associated with degenerative eye diseases. A Harvard Medical School study conducted on 349 individuals of 55 to 80 years of age with the advanced, neovascular stage of AMD examined the relationship between intake of total and specific types of fat and risk for advanced AMD. Scientists found higher intakes of omega-3 EFAs were associated with a lower risk for AMD among individuals consuming diets low in linoleic acid, an omega-6 EFA.14 Similarly, higher frequency of fish intake tended to reduce risk for AMD when the diet was low in linoleic acid. The researchers concluded diets high in omega-3 EFAs and fish were inversely associated with risk for AMD when intake of linoleic acid was low.
Several botanicals serve to protect the eye from oxidative injury, including Gingko biloba. In a study conducted at the L. V. Prasad Eye Institute, India, ginkgo biloba was found to be an excellent scavenger of reactive oxygen and nitrogen radicals and inhibitor of oxidative modifications that occur to proteins in vitro.15 The researchers found ginkgo biloba enters intact cells and protects them from stress and from DNA breaks. It also effectively inhibits chemically induced apoptosis. The scientists concluded ginkgo biloba’s inherent antioxidant, antiapoptotic and cytoprotective action and potential anti-cataract ability appear to be some of the factors responsible for its beneficial effects. A rat study at Kagawa University School of Medicine, Japan, found extract of gingko biloba reduced ganglion cell loss in eyes with chronic, moderately elevated intraocular pressure and concluded pretreatment and early post-treatment with gingko biloba extract is an effective neuroprotectant in a rat model of chronic glaucoma.16
The bilberry may inhibit age-related macular degeneration of the eye, according to a study at the Creighton University Medical Center, Omaha, Neb., that evaluated the antiangiogenic, antioxidant and anticarcinogenic potential of six different berry extracts.17 Another study, conducted at Columbia University, New York, found by quenching singlet oxygen, bilberry reduced epoxidation of A2E—a pigment that accumulates in retinal pigment epithelial cells with aging and in some retinal disorders and has been implicated in the etiology of macular degeneration.18 Through anecdotal evidence, bilberries are also thought to benefit eyes by improving night vision, according to Yousry Naguib, Ph.D., technical services/new product developer for Los Angeles-based Soft Gel Technologies Inc., which produces VmA25+, a 25 percent bilberry extract. The ophthalmological benefits of bilberries were first reported by World War II pilots who ate bilberry jam and experienced an improvement in visual acuity at night, faster adjustment to darkness and quicker restoration of visual acuity after exposure to glare, Naguib said.
Green tea is another herb that has shown promise in the prevention of degenerative eye diseases. An in vitro study held at the Sun Yat-sen University of Medical Sciences, Guangzhou, China, found a constituent of green tea—(-)-Epigallocatechin-3-gallate—could inhibit the proliferation of cultured rabbit lens epithelial cells by inducing apoptosis, which suggests green tea may prevent lens opacity.19 Another study conducted at All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, found green tea reduced the incidence of cataract induced by subcutaneous injection of selenite in rats primarily by preserving the antioxidant defense system.20
Extract of French maritime pine bark is another beneficial botanical with applications in eye health. One of the ways pine bark promotes eye health is possibly by treating and preventing diabetic retinopathy. A review in International Ophthalmology written by researchers at Westfalische Wilhelms Universitat Munster, Germany, stated standardized extract of the bark of the French maritime pine (as Pycnogenol®, provided by Geneva-based Horphag Research) was tested for treatment and prevention of retinopathy in five clinical trials with a total number of 1,289 patients since the late 1960s, and in all of these trials was unequivocally shown to inhibit the progression of retinopathy and partly recover visual acuity.21 In these studies, Pycnogenol also was shown to improve capillary resistance and reduce leakages into the retina.
Two additional botanicals conducive to good eye health are grapeseed extract and black currant. In a rat study conducted in the Research and Development Division of Kikkoman Corp., Noda City, Japan, researchers found procyanidin-rich extract from grape seeds prevents cataract formation in hereditary cataractous rats.22 They concluded this was due to the extract’s procyanidins and their antioxidative metabolites by their antioxidative action. In a study produced at the University of Tsukuba, Tokyo, the effects of a black currant anthocyanosides (BCA) concentrate on factors including dark adaptation and visual fatigue were examined in a double blind, placebo-controlled, crossover study with healthy human subjects.23 Intake of BCA at three dose levels appeared to produce dosedependent lowering of the dark adaptation threshold, and significant improvement in visual fatigue.
Retailers should familiarize themselves with what their customers seek in an eye health product in order to retail effectively, according to Danna Pratte, president of Phoenix-based Nutritional Healing Labs. “The majority of customers are looking for an eye product that can provide preventive benefits as well as general eye health maintenance,” she said.
According to Robbert Bailey, marketing specialist for eye health with La Grange, Ill.- based Cognis Nutrition and Health, retailers can best serve their customers’ eye health needs by keeping abreast of the latest scientific research. “Retailers who keep apprised of important scientific studies that support their products will best serve their customers,” Bailey said. “They can keep informed by scanning credible Web sites such as those sponsored by the National Institutes of Health. Cognis provides educational materials at www.verisonline.org, including fact sheets and research summaries.”
Maltby agreed knowledge is the key to successful retailing of eye health products. “Retailers should ensure their staff have a good working understanding of nutritional agents such as lutein or other vitamins and minerals that can impact eye health so they can talk intelligently with customers, give good direction and separate fact from myth,” he said.
Fred Bomeny, chief executive officer of Boca Raton, Fla.-based Lifexpand, agreed that retailers should familiarize themselves with the benefits of basic eye health supplements, including vitamins C and E, carotenoids and zinc, in order to guide customers intelligently.
According to Line and Maltby, retailers should inform customers that their best defense against eye disease is regular eye exams, particularly as the majority of degenerative eye diseases progress unnoticed. Line, Maltby and Bailey agreed retailers should also remind customers to wear sunglasses to protect against light-induced damage to the photoreceptor cells of the retina.
Bailey pointed out retailers should ensure their customers seek out products with adequate amounts of active ingredients. “Retailers should be savvy label readers and be able to differentiate those products that contain enough key ingredients to be beneficial,” he said.
Retailers should use a holistic approach when helping their customers address their eye health needs, according to Paige Pistone, retail communications manager with Hauppauge, N.Y.-based Twinlab. “They should help customers focus on achieving optimal ‘health outcomes,’” Pistone said. “It’s not just about selling pills in a bottle; it’s about prevention and total health and wellness practices. Retailers can best serve customers by increasing their awareness of leading eye health issues, providing knowledge and education, and preventive tactics and measures to help reduce advanced risks.” Preventive tactics include a well-balanced diet, supplementation, regular exercise and avoiding tobacco smoke, Pistone added.
Regarding marketing ideas for retailers of eye health products, Bailey recommended the use of marketing materials provided by companies like Cognis. “Cognis has recently created a marketing tool designed to be shown at the retail level that is getting excellent results,” Bailey said. “A new video/DVD features the overall health benefits of Betatene® natural mixed carotenoids. Brand marketers can tailor the footage to include their products, helping to educate consumers in their purchasing decisions. Cognis also works with brand marketers to create POP displays and materials to help educate consumers.”
Pistone recommended eye health displays, educational seminars with a participating medical doctor, in-store coupons or literature offered in conjunction with local eye health doctors, and fliers for direct mail or bag stuffers to alert consumers of new eye health concerns or research.
“When it comes to nutrients that may support eye health, there are so many options that leave customers confused,” Pistone said. “They need help understanding which products are effective and for what and which are formulated based on credible, strong-supporting science.”
Eye Health References
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9. Bressler NM et al. “Potential public health impact of Age-Related Eye Disease Study results: AREDS report no. 11.’ Arch Ophthalmol. 121, 11:1621-4, 2003. http://archopht.ama-assn.org.
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11. Richer S et al. “Double-masked, placebo-controlled, randomized trial of lutein and antioxidant supplementation in the intervention of atrophic age-related macular degeneration: the Veterans LAST study (Lutein Antioxidant Supplementation Trial).” Optometry. 75, 4:216-30, 2004.
12. B Olmedilla et al. “Lutein in patients with cataracts and age-related macular degeneration: a long-term supplementation study.” Journal of the Science of Food and Agriculture. 81, 9:904-9, 2001. www3.interscience.wiley.com/cgi-bin/jhome/1294
13. Neuringer et al. “Nutritional Manipulation of Primate Retinas, I: Effects of Lutein or Zeaxanthin Supplements on Serum and Macular Pigment in Xanthophyll-Free Rhesus Monkeys.” Investigative Ophthalmology & Visual Science. 45, 9: 3234-3243, 2004. http://www.iovs.org.
14. Seddon JM et al. “Dietary fat and risk for advanced age-related macular degeneration.” Arch Ophthalmol. 119, 8:1191-9, 2001. http://archopht.ama-assn.org
15. Thiagarajan G et al. “Molecular and cellular assessment of ginkgo biloba extract as a possible ophthalmic drug.” Exp Eye Res. 75, 4:421-30, 2002. www.sciencedirect.com/science/journal/00144835
16. Hirooka K et al. “The Ginkgo biloba extract (EGb 761) provides a neuroprotective effect on retinal ganglion cells in a rat model of chronic glaucoma.” Curr Eye Res. 28, 3:153-7, 2004. www.szp.swets.nl/szp/journals/ce.htm
17. Bagchi D et al. “Anti-angiogenic, antioxidant, and anti-carcinogenic properties of a novel anthocyanin-rich berry extract formula.” Biochemistry (Mosc). 69, 1:75-80, 2004. http://www.protein.bio.msu.su/biokhimiya
18. Sparrow JR et al. “A2E-epoxides damage DNA in retinal pigment epithelial cells. Vitamin E and other antioxidants inhibit A2E-epoxide formation.” J Biol Chem. 278, 20:18207-13, 2003. www3.interscience.wiley.com/cgi-bin/jtoc?ID=29830
19. Huang W et al. “Growth inhibition, induction of apoptosis by green tea constituent (-)-epigallocatechin-3-gallate in cultured rabbit lens epithelial cells.” Yan Ke Xue Bao. Sep;16, 3:194-8, 2000.
20. Gupta SK et al. “Green tea (Camellia sinensis) protects against selenite-induced oxidative stress in experimental cataractogenesis.” Ophthalmic Res. 34, 4:258-63, 2002. http://content.karger.com/ProdukteDB/produkte.asp?Aktion=JournalHome&ProduktNr=223858
21. Schonlau F et al. “Pycnogenol for diabetic retinopathy. A review.” Int Ophthalmol. 24, 3:161-71, 2001. www.kluweronline.com/issn/0165-5701/contents
22. Yamakoshi J et al. “Procyanidin-rich extract from grape seeds prevents cataract formation in hereditary cataractous (ICR/f) rats.” J Agric Food Chem. 50, 17:4983-8, 2002. http://pubs.acs.org/journals/jafcau/
23. Nakaishi H et al. “Effects of black current anthocyanoside intake on dark adaptation and VDT work-induced transient refractive alteration in healthy humans.” Altern Med Rev. 5, 6:553-62, 2000. www.thorne.com/alternative/alter_main.html