乌鸦传媒

LONDON, Oct. 13 -- Some cases of age-related macular degeneration may arise from a combination of low plasma levels of antioxidants and exposure to blue light from the sun, a multinational European study suggested.

The combination more than tripled the risk of the eye disease among individuals with the lowest combined levels of antioxidants, Astrid E. Fletcher, Ph.D., of the London School of Hygiene and Tropical Medicine, and colleagues reported in the October issue of Archives of Ophthalmology.

"Lowering retinal exposure to blue light and ensuring that intake of key antioxidant nutrients is sufficient are the main recommendations from our study," the authors concluded. "Any benefit from reducing sun exposure must be set against the benefits of sunlight, in particular its role in vitamin D synthesis."

"We advise reducing ocular exposure when outdoors by wearing broad-brimmed hats and sunglasses, estimated to reduce ocular light exposure by approximately 40% and 70%, respectively."

Sun exposure poses a well-established risk to the eyes, but different wavelengths inflict damage on different eye structures. Whereas the cornea and lens absorb ultraviolet light, the retina is exposed to visible light, including blue light.

Antioxidants protect the retina against the harmful effects of blue light exposure, the authors said. Inconsistent data have come from studies of associations between sun exposure and age-related macular degeneration. Moreover, interactions between sunlight exposure and antioxidants have received scant attention.

To improve understanding of associations among sun exposure, antioxidants, and age-related macular degeneration, investigators in the European Eye Study (EUROEYE) evaluated populations throughout Europe.

EUROEYE involved 4,753 participants older than 65, who all provided blood samples, underwent fundus photography, and answered a dietary questionnaire. Sun exposure was estimated from participants' self-reported information about work, outdoor activities, use of hats, and eyewear (including contact lenses, glasses, and sunglasses).

Complete data were available for 101 participants with neovascular age-related macular degeneration, 2,182 participants with early-stage age-related macular degeneration, and 2,117 controls.

By itself, blue-light exposure had no associations with neovascular or early-stage age-related macular degeneration. However, analysis of blue-light exposure by antioxidant quartile revealed consistent and significant association with neovascular age-related macular degeneration among those in the lowest quartile of vitamin C, vitamin E, zeaxanthin, and dietary zinc (odds ratio of about 1.4 per standard unit deviation increase in blue-light exposure).

The odds ratios for neovascular age-related macular degeneration were further increased among those with the lowest combined antioxidant levels, particularly the combination of vitamin C, zeaxanthin, and vitamin E (OR 3.7, 95% CI 1.6 to 8.9). Similar associations were observed for early-stage age-related macular degeneration.

"In the absence of cost-effective screening methods to identify people in the population with early AMD, we suggest that recommendations on ocular protection and diet target the general population, especially middle-aged people," the authors said.

The study was supported by the European Commission Vth Framework, the Macular Disease Society, the Estonian Ministry of Education and Science, the Spanish Ministry of Health, Centro de Investigacion Biomedica en Red de Epidemiologia y Salud Publica, and by Generalitat Valenciana. Multiple co-authors disclosed financial relationships with commercial interests.

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