Macular Degeneration

P>Description

Macular degeneration is a disorder in which the central portion of the retina becomes damaged due to hardening and obstruction of the retinal arteries.

Cause

Research suggests that long term exposure to light, particularly blue and ultraviolet light, damages the retina and contributes to the development of macular degeneration.

Types

Dry Form: Involves a deterioration of the retinal pigment epithelial cells of the macula; these cells support and nourish the retina. As the cells degenerate the cones of the macula are no longer supported and they gradually die. This process occurs very slowly, over several years, and is limited to the central part of vision. This form accounts for about 85% of macular degeneration cases.
Wet Form: Involves the growth of abnormal blood vessels behind the retina which may rupture and leak blood or fluid, causing the retina to lift or separate from the eye. Visual loss occurs rapidly as the blood vessels grow into the area of central vision. This form is less common and potentially more damaging. It can be treated in its early stages with laser surgery.
Pigment epithelium detachment: Involves the formation of a blister underneath the retina, causing blurring and distorted vision. It may develop in eyes with dry or wet macular degeneration or it may occur alone.

At Risk

Low levels of antioxidant vitamins and minerals have been associated with a higher incidence of macular degeneration. Other risk factors include heredity, light eye pigmentation, (i.e. blue eyes) cigarette smoking, and gender. Women appear to be at higher risk than men.

Prevention and Management

General:

There is at present no surgical or medical cure for the dry form of macular degeneration. The wet from is treated with laser surgery.
Research suggests that sunglasses which block ultraviolet and blue light helps to slow the progression.

Nutritional Influences:

Antioxidant vitamins^1,2 A^3,4, C^5,6, E^7,8, and the minerals selenium^9,10 and zinc^11,12 appear to be beneficial in reducing the rate of progression, and may improve vision in some individuals.
A small, controlled study found that ginkgo biloba extract had a beneficial effect on the vision of patients with macular degeneration.¹³

Abstracts

Snodderly DM. Evidence for protection against age-related macular degeneration by carotenoids and antioxidant vitamins. Am J Clin Nutr 1995 Dec; 62(6 Suppl):1448S-1461S. Epidemiologic data indicate that individuals with low plasma concentrations of carotenoids and antioxidant vitamins and those who smoke cigarettes are at increased risk for age-related macular degeneration (AMD). Laboratory data show that carotenoids and antioxidant vitamins help to protect the retina from oxidative damage initiated in part by absorption of light. Primate retinas accumulate two carotenoids, lutein and zeaxanthin, as the macular pigment, which is most dense at the center of the fovea and declines rapidly in more peripheral regions. The retina also distributes alpha-tocopherol (vitamin E) in a nonuniform spatial pattern. The region of monkey retinas where carotenoids and vitamin E are both low corresponds with a locus where early signs of AMD often appear in humans. The combination of evidence suggests that carotenoids and antioxidant vitamins may help to retard some of the destructive processes in the retina and the retinal pigment epithelium that lead to age-related degeneration of the macula.

Richer S. Multicenter ophthalmic and nutritional age-related macular degeneration study--part 2: antioxidant intervention and conclusions. J Am Optom Assoc 1996 Jan; 67(1):30-49. BACKGROUND: The experimental design, subjects, procedures and baseline data for the prospective double blind dry ARMD-antioxidant intervention study have been described in Part 1. METHODS: At eight DVA medical centers, 32 patients (group one) were assigned a placebo and 39 patients (group two) a "broad spectrum" antioxidant capsule. Data was collected in five areas: demographic; ophthalmic; dietary analysis of daily food intake; serum analysis; and adverse gastrointestinal symptoms. Data was serially acquired at baseline, 6 months, 12 months and 18 months, and was analyzed by univariate repeated factors ANOVA, p = 0.05. RESULTS: Group two (antioxidant po BID) maintained their distance LogMAR visual acuity (p = 0.03), while there was a trend toward both stabilized near M print (p = 0.07) and 6 cycle/degree contrast sensitivity (p approximately 0.10), in left eyes. However, group two (antioxidant) also had increased cortical opacification of the right lens (p = 0.04), compared to group one (placebo). Self perceived stabilization of vision was reported by subjects in group two and supported the objective data (Pearson chi square; p = 0.05). CONCLUSIONS: A specific 14 component antioxidant capsule taken twice daily stabilized but did not improve dry ARMD over the study period of 1.5 years. The ARMD stabilized eyes had less advanced disease functionally but not by fundus appearance. Decreased intake of cardioprotective nutrients (vitamin E, zinc, magnesium, B6 and folate) in ARMD patients remained constant over the course of the trial.

References

¹ Lebuisson DA, Leroy L, Rigal G. Traitement des degen-erescences "Maculaires seniles" par lextrait de Ginkgo biloba. Presse Med 1986; 15:1556-8.
² Newsome D et al. The trace element and antioxidant economy of the human macula: can dietary supplementation influence the course of macular degeneration? J Am Coll Nutr 10(5):536, 1991.
³ Underwood EJ. Trace Elements in Human and Animal Nutrition. 4th ed. London:Academic press;1977. p 198.
⁴ Crary EJ. Smyrna, Georgia, USA- quoted in Zarrow S. Keep your eyes young and sharp. Prevention 1985 March; p 74-80.
⁵ Todd GP. Nutrition, Health & Disease. Norfolk (VA):The Donning Company;1988
⁶ Robinson WG Jr et al. Vitamin E deficiency and the retina: photoreceptor and pigment epithelial changes. Invest Ophthalmol Vis Sci 1979;18(7):683-90.
⁷ Robinson WG Jr et al. Vitamin E deficiency and the retina: photoreceptor and pigment epithelial changes. Invest Ophthalmol Vis Sci 1979;18(7):683-90.
⁸ Organisciak DT et al. The protective effect of ascorbate in retinal light damage of rats. Invest Ophthalmol Vis Sci 1985;26 (11):1580-8.
⁹ Li ZY et al. Amelioration of photic injury in rat retina by ascorbic acid: a histopathologic study. Invest Ophthalmol Vis Sci 1985;26(11):1589-98.
¹⁰ Hayes KC. Retinal degeneration in monkeys induced by deficiencies of vitamin E or A. Invest Ophthalmol 1991;13(7):499-510.

¹¹ Goldberg J et al. Factors associated with age-related macular degeneration. An analysis of data from the first National Examination Survey. Am J Epidemiol 1988;128(4): 700-10.
¹² Eye Disease Case-Control Study Group. Antioxidant status and neovascular age-related macular degeneration. Arch Ophthalmol 1993;111:104 -9.
¹³ Seddon J. Dietary carotenoids, vitamins A,C,and E, and advanced age-related macular degeneration. JAMA 1994;272(18):1413-20.