Eye protection & antioxidants, keys to prevent AMD

Research highlights the need for effective screening tools and education campaigns similar to those created for skin cancer

Vicious cycle in early AMD initiated by blue light
Source: Albert Augustin, M.D.

Do the medical community and governments around the world need to launch public education and prevention campaigns for age-related macular degeneration (AMD), similar to efforts to prevent skin cancer? Physicians say recent research supports such an approach.
Research published in the October 2008 issue of the Archives of Ophthalmology by Paulus T. V. M. de Jong, M.D., Ph.D., Department of Ophthalmogenetics, Institute for Neuroscience, Amsterdam, Netherlands, and colleagues examined the association of sunlight exposure and antioxidant levels with AMD.
They found that although it is not possible to establish causality between sunlight exposure and neovascular AMD, their results suggested that people in the general population should use ocular protection and follow dietary recommendations for “key antioxidant nutrients.”
“Ocular protection and avoiding sunlight in the middle of the day is particularly important in people whose intraocular lenses have no yellow filter,” wrote Dr. de Jong and colleagues.
That is good advice, said Jie Jin Wang M.Med., Ph.D., epidemiologist, Department of Ophthalmology, Westmead Millennium Institute, University of Sydney, Sydney, Australia, who, with Paul Mitchell, M.D., Ph.D., has extensively studied risk factors for AMD in the Blue Mountains Eye Study in Australia.
“I think that the authors’ recommendations to the general population are appropriate and should benefit the public not only in regards to AMD prevention, which needs confirmation, but also regarding skin cancer prevention and an overall healthy lifestyle and healthy aging,” she said.
The study involved 4,753 participants aged 65 years or older in the European Eye Study, who underwent fundus photography, were interviewed for adult lifetime sunlight exposure, and gave blood for antioxidant analysis. Blue light exposure was estimated by combining meteorologic and questionnaire data.
The authors’ support for prevention measures was based in part on a lack of cost-effective screening methods for people in the population with early AMD. Albert Augustin, M.D., professor of ophthalmology and director, department of ophthalmology, Augenklinik, Karlsruhe, Germany, said that the findings indicate that there is a need for establishing such screening methods.
“Until these methods are available, dietary recommendations should be followed,” Dr. Augustin said.
The dietary recommendations of the study’s authors stemmed from their finding significant associations between blue light exposure and neovascular AMD in individuals in the lowest quartile of antioxidant levels, including for vitamin C, zeaxanthin, vitamin E, and dietary zinc. The study participants were found to have higher odds ratios for neovascular AMD and early stage AMD if exposed to blue light combined with low antioxidant levels, especially vitamin C, zeaxanthin, and vitamin E.
Dr. Wang said it was important that the study found that the combination of blue light exposure and low plasma concentrations of antioxidants was associated with the early stages of AMD.
“Compared to late stage AMD, the neovascular form and geographic atrophy, we know less about risk factors for early AMD,” she said. “In order to be able to have primary prevention of AMD—preventing onset of early AMD—this knowledge is highly important. Early AMD is by far the most significant risk factor for late AMD, a leading cause of irreversible visual impairment in older persons”

Age-related susceptibility?

The researchers also hypothesized that blue light may be more damaging in middle-age adults than in younger adults because low plasma concentrations of antioxidants are common in the older population.
Dr. Augustin cautioned that the issue is more complex. For example, in middle age the fatty acid composition of the photoreceptor outer segments of the retina changes to make the retina more susceptible to light damage. But it remains unclear whether such changes make blue light more damaging than it is for younger eyes.
Dr. Augustin agreed with the authors that it is unlikely that their results could be explained solely by genetic susceptibility to the effects of blue light.
“Currently there is no proof, not even a sign, that there is genetic susceptibility to the effects of blue light,” he said. “I am convinced that environmental medicine will prove this in the near future.”
The impact of the recent research on Dr. Augustin’s practice may be limited because he already recommends eye protection and a similar diet to his middle-aged patients.
“This study was further support of my way to treat those patients,” he said.
The findings from this study showing the combined effect from low antioxidant levels and blue light exposure adds to the knowledge of how multiple factors interplay to render an individual susceptible to AMD, Dr. Wang said. As those factors and their interplay patterns become clearer, their impact on physicians providing individualized medicine will become stronger.
Future research may consider community-based primary prevention trials. Previous intervention trials on AMD were exclusively clinic-based secondary prevention—the prevention of late AMD in patients with early AMD.
Other areas of AMD that require further examination are the possible roles of in-house light sources, and the impact of blue light-filtering lenses also should be studied in more detail, Dr. Augustin said.

Editors’ note: Drs. Wang and Augustin have no financial interests related to their comments.

Contact information

Augustin: +49 172 252 1726, albertjaugustin@googlemail.com
Wang: +61 2 9845 5006, jiejin_wang@wmi.usyd.edu.au