Chronic, age-related visual problems such as cataract, macular degeneration and glaucoma have one basic similarity. These are degenerative conditions caused by excessive oxidation (free radical damage). Remember that free radicals are toxic by-products of your everyday metabolism. With aging, the production of these free radicals increases, whereas your body defences against them (i.e. the production of natural antioxidants in an attempt to neutralise free radicals) becomes less effective. As a result, free radicals destroy proteins, enzymes and DNA causing chronic damage to your tissues.
So, this is oxidation in a nutshell. Apart from oxidation, another important process implicated in aging is that of glycation. This is when sugar and similar molecules attack your proteins and DNA, causing abnormal chemical bonds between individual molecules. Free radicals then make matters worse by facilitating this destruction of your tissues. In the end, there is an increased amount of abnormal, twisted and deformed proteins in your body, worsening the risk of developing age-related chronic conditions. In the case of the eye, these deformed proteins may cause visual impairment through cataract, macular degeneration or glaucoma.
Cataract
Cataract is a common age-related condition and affects one in four people over the age of 65. Basically, it is caused when the proteins inside the lens of the eye (called crystallins) become damaged. Glycation is the main culprit here, which causes the crystallins to bind to each other, clump together and become misshapen, forming opaque plaques in the lens of the eye.
As a result, light cannot pass through the lens and reach properly the inside of the eye, so vision is impaired. This progressive damage is made worse by free radical action on the already damaged crystallins. For more detailed information about cataract see my most recent book The Cataract Cure.
Age-Related Macular Degeneration (ARMD)
Another degenerative condition is ARMD. This happens when a particular part of the retina, called the macula, becomes damaged by free radicals that cause the arteries and cells of the retina to malfunction.
Environmental pollution, increased ultraviolet (UV) radiation or other toxic damage, cause and increased production of free radicals in the retina. So, a logical way of preventing or treating ARMD is by using antioxidants to reduce the concentration of free radicals in the eye (1). The use of antioxidants in preventing ARMD has been studied in a variety of scientific trials, usually with positive results. For example, it was recently reported from the Department of Ophthalmology, Biochemistry, and Medicine, Emory University, Atlanta, Georgia in the US, that antioxidants prevent oxidation of vital amino acids in patients with ARMD (2).
The role of oxidation as a cause of ARMD was explored further by a team of researchers from the Chemistry and Biochemistry Department, Northern Illinois University. The researchers suggested that one of the reasons why the macula is easily affected by free radicals is because, with aging, the melanin pigment of the retina loses its ability to withstand damage (3). It makes sense to suggest that, in order to prevent this deterioration of the melanin pigment, antioxidant therapy must be helpful.
Glaucoma
The third most common chronic eye condition is glaucoma. This is when the fluid inside different parts of the eye does not flow properly, causing increased pressure inside the eye with consequent loss of vision. The blockage is caused when free radicals damage the trabecular meshwork, a part of the eye that produces and then reabsorbs the fluid.
Italian scientists from the Department of Health Sciences, University of Genoa, have recently reported the following: “There is growing evidence that reactive oxygen species (free radicals) play a key role in the pathogenesis of glaucoma. The occurrence of oxidative DNA damage in the trabecular meshwork has been demonstrated by measuring the increase of 8-hydroxy-2′-deoxyguanosine, the most abundant DNA oxidative alteration, which is significantly increased in glaucoma-bearing subjects as compared to unaffected controls.”
They believe that there are several factors supporting the theory that free radicals play a fundamental role in glaucoma. Some of these reasons are:
The scientists concluded: “These considerations could bear relevance for glaucoma prevention and suggest that … the use of drugs or dietary measures attenuating the effects of free radicals could be useful tools contributing to the control of this disease.” (4)
In summary, these three chronic eye conditions develop on a background of both oxidation and glycation. It is logical to assume that in order to prevent or even reverse this damage is necessary to use a combination of chemicals which work both against oxidation (i.e. antioxidants) and against glycation.
N-acetylcarnosine
The most recent development in the prevention of age-related eye diseases is the nutrient N-acetyl-carnosine. This is a natural chemical closely related to carnosine, which itself is a combination of two amino acids (alanine and histidine). Carnosine has been investigated extensively and there are over 1000 scientific reports discussing its biological actions. It is active in almost all body tissues and works both as an antioxidant and as an anti-glycator.
N-acetylcarnosine (NAC) works the same way as carnosine, namely preventing free radical damage and reducing the risk of glycation. But NAC is particularly useful within the eye, because it remains biologically active for longer. Once inside the eye tissues NAC transforms into pure carnosine and prevents free radicals from further destroying eye tissues such as the crystallins. It also reverses glycation, in other words, it may be useful in curing already existing eye damage. N-acetylcarnosine is a very important discovery because it shows that cataract may be cured without the need to resort to an operation (5).
Commercially available N-acetylcarnosine: The beneficial actions of NAC against cataract and other eye conditions have been recognised by a variety of commercial companies who are now offering NAC in eye drop form. However, it is important to realise that NAC is very sensitive both during the manufacturing and during the application stages, so it is necessary to use only a reputable supplier. Also, some commercial eye drops contain chemicals which may not be beneficial when applied directly in the eye. For example, although vitamins given by mouth may help prevent age related eye conditions as will be discussed below, if these vitamins are given directly into the eye, they may cause damage to the eye tissues. In addition, the Russian scientists who developed the original NAC drops (Can-C) claim that the combination of stabilising agents and other chemical factors needs to be taken into account when using NAC and this makes their Can-C drops the best available choice at present.
Apart from carnosine, other good anti-glycators are the agents metformin and aminoguanidine. Both work to reduce the risk of glycation of proteins within the lens of the eye and thus prevent the harm caused to the proteins of the lens. By helping to improve microcirculation of the blood in the eye these can be useful both in macular degeneration and glaucoma.
By-products of glycation (called AGEs –Advance Glycation End-products) are frequently found in several parts of the eye, including the retina (6). It has now been proven that there are special receptors for these AGEs within the retina and this means that the blueprint for the slow and chronic destruction of the retina has already been put in place by nature. (7) However, antiglycators such as carnosine, metformin and aminoguanidine can fool nature by reducing AGEs before these have the chance to combine with the receptors and affect the eye.
It may not be enough to only use one remedy in order to prevent or even reverse chronic eye conditions. Taking additional supplements will ensure that you are getting the extra insurance necessary to keep free radical action at low levels and reduce the risk of further harm to the eyes. The following are some relevant nutritional factors that have a role to play in improving vision. Current research supporting their actions is highlighted for each supplement.
Ginkgo Biloba Extract
Ginkgo is the extract of the maidenhair tree, used in order to improve memory and blood circulation problems. It is also a very good antioxidant, particularly if used correctly. Many people buy the ‘raw leaf’ preparation of ginkgo which may not contain a standard amount of the active ingredients. It is best to use the standardised extract at a dose of 120 mg once or twice a day.
Scientists from the Department of Ophthalmology, Tang Du Hospital, Shanxi in China have studied the effects of ginkgo extracts on the retina. They first injected glutamate (a known brain chemical which is toxic in high amounts) into the retinas of one group of rabbits. This caused an increased production of free radicals which, in turn, caused the retinal cells to wither and die. They then injected ginkgo biloba extracts into another group of rabbits before injecting them with glutamate. What they found was that ginkgo protected these retinas from any harm caused by free radicals. (8) This confirms that ginkgo may be able to protect the retina against age-related oxidation, and that gingko may thus be useful against all chronic eye conditions including macular degeneration.
Although this particular experiment was performed on laboratory animals, newer research has confirmed that ginkgo can also be useful in human eye problems. In a clinical trial performed by Polish researchers from the Department of Clinical Ophthalmology, Medical Academy of Poland, gingko was given to a group of 15 patients who had an increased risk of retinal damage (in this case through diabetes). They found that ginkgo improved these patients’ colour vision test results, concluding that: “Ginkgo seems to be good adjuvant in patients with long lasting diabetes mellitus” (which can cause retinal damage). (9)
Finally, ginkgo can protect not only against macular degeneration, but also against cataract, by reducing the injury caused by oxidation on the lens of the eye. It turns out that ginkgo increases the antioxidant enzymes superoxide dismutase and glutathione peroxidase in the eye. This makes it less likely that free radicals caused by radiation, (such as UV for example) can damage the lens (10).
Grape Seed Extract
It is well known that both grapes and their seeds contain antioxidants such as flavonoids (catechin, epicatechin, procyanidins and gallic acid). These are strong natural chemicals with antioxidant power up to 20 times more than vitamin E, and 50 times more than vitamin C. Flavonoids from grape seeds help to protect the eyes from UV radiation and to improve overall vision. In addition, these compounds can help improve blood circulation particularly in the small arteries of organs including the eye. (11)
In a landmark experiment preformed by researchers from the Research and Development Division, Kikkoman Corporation, Japan, it was confirmed that grape seed extracts prevent the progression of cataract formation. The researchers investigated the anti-cataract activity of grape seed extracts (containing 38.5% procyanidins) on laboratory rats with cataract. The rats were divided into two groups. The first group was fed a standard diet containing no grape seed extracts. The second was given 0.213% grape seed extract in addition to the standard diet, for 27 days. As a result, the clarity of the lens was significantly better in the treatment group compared with the control group. The scientists concluded that: “these extracts significantly prevented and postponed development of cataract formation in the active group” (12).
Vinpocetine
Although vinpocetine is a well known nootropic (brain booster), it has also a role to play in preventing chronic eye conditions, particularly if used in combinations with other supplements.
Some years ago, scientists working at the Romanian University of Medicine and Pharmacy, have reported that diseases in other parts of the body, such as liver disease, can have an adverse impact upon the retina. Nutritional supplements such as vinpocetine can prevent this kind of damage by improving blood circulation both in the liver and in the arteries of the eye. In this way, the likelihood of visual problems associated with systemic diseases can be reduced. (13)
More recently, Russian scientists found that vinpocetine can improve optic nerve atrophy caused by head injury. It improved the sensitivity of the retina and protected the optic nerve which transmits visual signals from the eye to the brain. Finally, it improved blood flow within the arteries of the eye, which means that more nutrients could reach vital eye tissues. (14)
Lutein and zeaxanthin
The two most well known supplements for eye protection are the carotenoids lutein and zeaxanthin. There is quite a lot of scientific evidence confirming that consumption of these two chemicals reduces the risk of age-related cataract. Lutein and zeaxanthin are the only two carotenoids present in the lens, and their role is to protect the lens against free radicals caused by UV radiation from the sun.
In an experiment performed at the Ohio State University in the USA, scientists compared these two chemicals and vitamin E used against free radical action in lenses obtained from human eyes. They first applied the different chemicals (such as lutein, zeaxanthin, vitamin E, and astaxanthin – see below) on the lenses, and then they irradiated these lenses with UV radiation. They found that all these chemical protect the lens against free radical damage. Specifically, there was an inhibition of ‘cell stress signalling’, meaning that the irradiated cells did not produce any toxic chemicals following the irradiation. Lutein and zeaxanthin was more powerful than vitamin E in this respect. (15)
Astaxanthin
This is a carotenoid chemical similar to lutein and zeaxanthin. Common sources of natural astaxanthin are the green algae Haematococcus pluvialis, the red yeast, Phaffia rhodozyma and some shellfish. It is usually used to provide the pink colour of salmon and lobsters grown commercially. Astaxanthin, in association with lutein and zeaxanthin, is a very effective antioxidant within the eye. (16) Scientific interest in astaxanthin has only recently begun to spread, and there are reports that it can be useful in a variety of conditions including bowel, brain and heart problems.
Others
Apart from vitamins and nutrients, it is also necessary to protect your eyes in other ways. For example, avoid strong sunlight which facilitates free radical reactions within the eye. Instead wear good quality sunglasses, particularly if you live in a place where sunshine is strong. Wearing a hat is also a good idea, as it cuts down some of the harmful UV radiation reaching your eyes. Frequent eye tests will pick up any early signs of eye disease and will give you the chance of starting or modifying your prevention nutritional programme. If you have diabetes, are a smoker or have a family history of chronic eye disease, then prevention therapy becomes even more important.
References
1. Gakhramanov FS. Effect of natural antioxidants on antioxidant activity and lipid peroxidation in eye tissue of rabbits with chemical burns. Bull Exp Biol Med. 2005;140(3):289-91.
2. Moriarty-Craige SE, Adkison J, Lynn M, Gensler G, Bressler S, Jones DP, Sternberg P Jr. Antioxidant supplements prevent oxidation of cysteine/cystine redox in patients with age-related macular degeneration. Am J Ophthalmol. 2005;140(6):1020-6.
3. Wang Z, Dillon J, Gaillard ER. Antioxidant properties of melanin in retinal pigment epithelial cells. Photochem Photobiol. 2006;82(2):474-9.
4. Izzotti A, Di Marco B, De Flora S, Sacca S. Open angle glaucoma: epidemiology, pathogenesis and prevention. Recenti Prog Med. 2006;97(1):37-45.
5. Babizhayev M, Deyev A, Yermakova V, Brickman I, Bours J. Lipid peroxidation and cataracts: N-acetylcarnosine as the therapeutic tool to manage age-related cataracts in human and canine eyes. Drugs R D. 2004;5(3):125-139.
6. Kaji Y, Usui T, Oshika T, et al. Advanced glycation end products in diabetic corneas. Invest Ophthalmol Vis Sci. 2000;41(2):362-8.
7. Yamada Y, Ishibashi K, Bhutto IA, Tian J, Lutty GA, Handa JT. The expression of advanced glycation endproduct receptors in rpe cells associated with basal deposits in human maculas. Exp Eye Res. 2006;82(5):840-8.
8. Li YJ, Yang XG, Gao MR.Effects of extracts of ginkgo biloba (EGB) on levels of nitric oxide and apoptosis in the retina induced by glutamate in adult rabbits. Zhongguo Zhong Yao Za Zhi. 2003;28(10):961-4.
9. Bernardczyk-Meller J, Siwiec-Proscinska J, Stankiewicz W, Fichna P, Pecold K. Influence of Eqb 761 on the function of the retina in children and adolescent with long lasting diabetes mellitus–preliminary report. Klin Oczna. 2004;106(4-5):569-71.
10. Ertekin MV, Kocer I, Karslioglu I, Taysi S, Gepdiremen A, Sezen O, Balci E, Bakan N. Effects of oral Ginkgo biloba supplementation on cataract formation and oxidative stress occurring in lenses of rats exposed to total cranium radiotherapy. Jpn J Ophthalmol. 2004;48(5):499-502.
11. Shi J, Yu J, Pohorly JE, Kakuda Y. Polyphenolics in grape seeds-biochemistry and functionality. J Med Food. 2003;6(4):291-9.
12. Yamakoshi J, Saito M, Kataoka S, Tokutake S. Procyanidin-rich extract from grape seeds prevents cataract formation in hereditary cataractous (ICR/f) rats. J Agric Food Chem. 2002;50(17):4983-8.
13. Cusnir V, Slepova O, Dumbrava V, Zaiteva N, Cusnir R, Midrigan I. Ocular manifestations of hepatitis B. Oftalmologia. 1997;41(2):25-7.
14. Aznabaev MT, Khalikov VA, Zagidullina ASh. Use of instenon in complex treatment of patients with optic nerve atrophy caused by craniocerebral trauma. Vestn Oftalmol. 2003;119(6):12-4.
15. Chitchumroonchokchai C, Bomser JA, Glamm JE, Failla ML Xanthophylls and alpha-tocopherol decrease UVB-induced lipid peroxidation and stress signalling in human lens epithelial cells. J Nutr. 2004;134(12):3225-32.
16. Waagbo R, Hamre K, Bjerkas E, Berge R, Wathne E, Lie O, Torstensen B. Cataract formation in Atlantic salmon, Salmo salar L., smolt relative to dietary pro- and antioxidants and lipid level. J Fish Dis. 2003;26(4):213-29.
