Sun, Low Antioxidants Linked to Blindness

The combination contributes to age-related macular degeneration, study finds.

A new study published in the October issue of Archives of Ophthalmology has found that older people with low levels of certain antioxidants present in many fruits and vegetables, and who are exposed to short-wavelength blue light from the sun, are more likely to develop certain types of age-related macular degeneration (AMD). But the damage can begin decades before the average age of 60, when AMD starts to affect most.

AMD is the leading cause of blindness in adults over the age of 60, according to the U.S. National Eye Institute. The progressively worsening disease affects the macula portion of the eye, located in the center of the retina, which enables detailed vision.

The study, led by Astrid Fletcher, Ph.D., of the London School of Hygiene & Tropical Medicine, is the first to report in humans an adverse association between sunlight exposure and AMD in people with low levels of antioxidants.

The eye is particularly vulnerable to the damaging effects of sunlight. Ultraviolet radiation is absorbed by the lens, but visible or ‘blue’ light penetrates the retina allowing us to see. Protection against the harmful effects of blue light is provided by the antioxidant vitamins C and E, the carotenoids (lutein and zeaxanthin) which filter blue light, and zinc.

Animal and laboratory studies have previously shown that blue light may be a factor in the pathogenesis of AMD, but results have been inconsistent in the few studies that have investigated associations between sunlight exposure and AMD.

Study Results

The study 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.)

By itself, blue-light exposure had no associations with neovascular or early AMD. However, analysis of blue-light exposure by antioxidant quartile revealed consistent and significant association with neovascular AMD among those in the lowest quartile of vitamin C, vitamin E, zeaxanthin, and dietary zinc.

“We recommend that people use eye protection, including sunglasses and wide-brimmed hats, if going outside and especially in bright sunlight,” and during the middle of the day, said Fletcher.

“Our advice on nutrition,” she added, “is that people should ensure that they follow the five-a-day recommendations. In particular, they should see that their diet includes leafy green vegetables, citrus fruits, vegetable oils and nuts, as these are good sources of the antioxidant vitamins of relevance to the retina.”

“This is the first time they’ve looked at this in so many patients, but it makes sense from a physiological standpoint,” said Dr. David M Kleinman, an assistant professor of ophthalmology at the University of Rochester Eye Institute. “In addition to there being some things we can’t control, like genetic predisposition, really taking care of ourselves in a certain way will really help reduce vision loss from AMD.”

That includes exercising and controlling blood pressure and cholesterol, added Kleinman, a retina specialist who studies macular degeneration.