Macular Degeneration

Introduction

What should I know about Macular Degeneration?

Macular degeneration is a major cause of gradual, painless, central vision loss in the elderly. (1) Previously known as "senile macular degeneration," the name has been changed to age-related macular degeneration, (ARMD), due to the unflattering reference to advanced age. The average age at onset of visual loss is about 75 years. After the age of 50 years, the incidence steadily increases; over one-third of people in their ninth decade of life are affected. (2) The actual incidence of the disease depends upon how it is defined. The Framingham Eye Study revealed that ARMD affects about 2% of Americans aged 52-64 years: 11% aged 65-74 years; and 28% aged 75 years and older. (3)

Despite its prevalence there is a lot about macular degeneration that remains unclear. Researchers have implied that certain conditions may contribute to the disorder. Some of these are arteriosclerosis, oxidative damage, photic damage, inflammation, diet, vitamin and rare element deficiencies, and genetics. The genetic factors that are suspected in being involved are hard to quantify due to the fact that parents and siblings may not be alive, and children may be too young to display any symptoms that could be traced leading to the disease. A recent study has suggested that depression may contribute to ARMD as well. (4)

As with most diseases, however, it has been determined that there are some apparent risk factors that are associated. Two of these are hypertension and cigarette smoking. Other suggested risk factors include far-sightedness and the normal risk factors associated with cardiovascular disease. Years ago, scientists thought there was a relationship between light and the development of ARMD. However, more recent studies found no correlation to either visible light nor a light iris color and increased risk. More recently, the role of ocular blood flow in ARMD has been studied to see if there is a relationship between blood flow and the disease itself. (5)

Statistic

World Health Organization, 2004.

  • Age-related macular degeneration (AMD) ranks third on the global scale.
  • However, in developed countries, AMD is the leading cause of blindness

New Zealand Medical Association, 2001.

  • 4984 New Zealanders registered blind have AMD in the 55 year and over age group.

Macular Degeneration Foundation, 1999.

    1 in 3 Americans are affected. Macular Degeneration is the leading cause of central vision loss and blindness in the Western World. Over 15 million victims have this disease.

American Academy of Ophthalmology, 1999.

    90% of cases are "Dry" form. 10% of cases are "Wet" form.

The Schepens Eye Research Institute, 1999.

    "Wet" form accounts for 90% of all cases of legal blindness.

Signs and Symptoms

[span class=alert]The following list does not insure the presence of this health condition. Please see the text and your healthcare professional for more information.[/span]

Ophthalmologists can detect the presence of macular degeneration during a complete examination by observing the changes in and behind the retina. Small yellow clusters of deposits occur that can only be seen through an ophthalmoscope. Age related macular degeneration occurs in both eyes, is occasionally treatable, not preventable, and generally worsens over time. While some patients may have no symptoms, the symptoms most commonly seen include blurred central vision, decreased reading ability, especially in dim light, distortion in central vision, and trouble adapting to darkness. Macular degeneration occurs most often in patients over 50 years old.

General

  • Increasingly blurred central vision
  • Decreased reading ability, especially in dim light
  • Distortion in central vision
  • Trouble adapting to darkness
  • Occurs most frequently in both eyes
  • Occurs most often in patients over 50 years old

Treatment Options

Conventional

So far, successful treatment to stop the visual loss has been difficult for researchers to find. While vitamin supplementation (especially antioxidants) and zinc supplementation have been proposed, their benefits are still a question that the scientific community has yet to prove conclusively (6) and the actual results of supplementation have not been approved as safe and effective. (7)

One specific type of ARMD responds well to a therapy called laser photocoagulation. The goal of this treatment is to decrease the risk of additional vision loss. Restoring the vision that has been lost is rare.

Nutritional Suplementation


Zinc

Studies have reported lower serum zinc levels in individuals with macular degeneration. (8) , (9) The Age Related Eye Disease Study (AREDS) Report # 11 found that if individuals at risk for ARMD took antioxidant supplements with zinc, their risk would be lessened and over a 5 year period of time the impact on public health would be significant. (10) However, other authors report finding either no association, or elevated serum zinc levels in patients with macular degeneration, so there is some uncertainty surrounding this issue. (11) , (12)


Lutein, Zeaxanthin

These are the primary carotenoids comprising the macular pigment of the eyes. In addition to acting as optical filters, evidence suggests that they also function as antioxidants in the human retina. (13)

Inverse relationships have been reported between the incidence of age-related macular degeneration (ARMD) and the combined levels of lutein and zeaxanthin intake in the diet, and also their concentration in the blood serum. The results of a study that evaluated these associations supported the hypothesis that low concentrations of lutein and zeaxanthin in the macular pigment may be associated with an increased risk of age-related macular degeneration. (14) However, this issue is not completely settled because the authors of another study reported finding no association between the serum levels of lutein and zeaxanthin and age-related macular degeneration (15) which has been further supported by data collected from the third National Health and Nutrition Examination Survey (NHANES). (16)

Foods with high lutein and zeaxanthin content include green leafy vegetables, egg yolk, corn, orange peppers, kiwi fruit, grapes, spinach, orange juice, zucchini, and different kinds of squash. (17)


Lycopene

Lycopene is a very abundant carotenoid. One study reported that individuals with very low levels of lycopene were twice as likely to have age-related macular degeneration as those with higher levels. Surprisingly, this study also reported finding that serum levels of the carotenoids that predominate in the macular pigment (lutein and zeaxanthin) were unrelated to ARMD. (18)


Vitamin E

Much of the research on the etiology of age-related macular degeneration and other eye diseases has focused on the role of nutritional antioxidants. Evidence from epidemiological studies suggests that nutritional antioxidants, such as vitamin E, may play a role in delaying the onset of these age-related vision disorders. (19) It is now known that vitamin E is distributed within retinal tissues. (20) Some research results indicate that patients with age-related macular degeneration have lower serum vitamin E levels compared to age-matched controls. (21)


Vitamin C

Again, the verdict is out on whether or not vitamin C can play a role in ARMD. Some studies say yes, (22) and other studies report finding that vitamin C levels are not associated with a reduced risk at all. (23) , (24)

Herbal Suplementation


Bilberry

Bilberry is one of the most popular herbs on the market today. During World War II when British air pilots ate bilberries, they reported an improved ability to adjust to glare, an increase in their visual acuity, and nighttime vision. (25) Bilberry extracts show promise in the areas of diabetic retinopathy, macular degeneration, cataracts, glaucoma, and varicose veins. (26) Bilberry is an excellent antioxidant. (27) With age, oxidative stress due to free radicals increases in some people more than in others. This damage to ocular tissues may lead to various eye pathologies. If it improves the oxygenation of tissue, bilberry may show promise in the areas of prevention for diabetic retinopathy, minimizing the advance of macular degeneration, and arresting cataract progression. (28) , (29) , (30)


Grape Seed Extract

Proanthocyanidins (PCO's), the active constituent in grape seed, is a flavonoid-rich compound which is being heavily touted as one of the most potent free radical scavengers. It has been reported to enhance the absorption of and work synergistically with vitamin C. (31) If oxidation is a risk factor in ARMD, it would stand to reason that grape seed would be a promising free radical scavenger to use.


Green Tea

Again, this theory rests on the research that supports the role of antioxidants in ARMD. Green tea reportedly has antioxidant properties (32) and the ability to protect against oxidative damage of red blood cells. (33) Antioxidants protect cells and tissues of many biological systems including the eyes against oxidative damage and injury. (34) It is important to note that the addition of milk to any tea may significantly lower the antioxidant potential. (35)

References

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