Environmental Factor, September 2011, National Institute of Environmental Health Sciences
NIEHS investigator links UV exposure and aging to cataracts and macular degeneration
Presently a professor in the Department of Chemistry at Fordham University, Roberts earned her Ph.D. in organic chemistry from St. John's University in New York, before completing a postdoctoral fellowship in pharmacology at the Albert Einstein College of Medicine. (Photo courtesy of Steve McCaw)
Genetics, ethnicity, and gender have long since been established as key contributors to ocular disease in adults. However, during a July discussion surrounding her latest work on the effects of light on the human eye, NIEHS researcher Joan Roberts, Ph.D., suggests that the aging process itself, in conjunction with excessive UV exposure, plays a major role in the onset of cataracts and macular degeneration.
“While light itself is not necessarily dangerous to the eye, under the right circumstances it most certainly can be,” explains Roberts(http://faculty.fordham.edu/jroberts/) , a volunteer investigator with the Laboratory of Toxicology and Pharmacology and an expert on ocular disease. “It all depends on the light's intensity, wavelength, mechanism, and the age of the person receiving it.”
Chromophores - the eye's energy filters
The backbone for Roberts' claim is the progression of ocular changes that occur in many adults age 40 and above, particularly those involving light-absorbing chemicals called chromophores.
“During childhood and young adulthood, chromophores function as energy filters for many of light's harmful effects,” Roberts notes. “However, as we get older, the eye encounters a noticeable buildup of phototoxic chromophores such as xanthurenic acid and lipofuscin that, when irradiated, can cause significant damage. Furthermore, this is happening at a time when the body's natural defenses to these agents are in a state of decline, due to a gradual loss of protective antioxidants and enzymes.”
Moderating the ravages of aging
In the end, Roberts and her colleagues admit that, while various diseases such as cataracts and macular degeneration may ultimately be inevitable with age, steps can be taken to minimize their effects, if not avoid them altogether.
Conventional thinking has offered a variety of suggestions regarding ocular protection and cataract prevention. Be it wraparound sunglasses with specific UV protective lenses or a steady diet of antioxidant-rich fruits and vegetables, Roberts believes all are good ideas, though she firmly insists that the key to prevention lies in a strictly balanced approach.
“It's important to remember that different antioxidants prevent ocular disease in different ways,” she emphasizes. “Omega-3s prevent inflammatory response, while lutein is great for singlet oxygen prevention. Both are wonderful ideas, but only when consumed in the proper amounts. When antioxidants are taken incorrectly, you're actually adding a pro-oxidant, which could conceivably damage the very tissue you're trying to protect.”
“One out of every three people will develop macular degeneration by the time they're 85, so effective prevention is all about starting now,” she concludes. “Particularly with younger children whose retinas aren't yet fully protected, let's shut out the lights when we don't need them and eat a little more spinach at dinner. When we're out on the beach or the snow, let's wear the right eyewear to protect us from reflective light. The fact is, most people will develop cataracts by the time they're 70, but, by taking the right precautions, we can at least stave off their effects as long as possible.”
Citations for recent research:
Ehrenshaft M, Zhao B, Andley UP, Mason RP, Roberts JE(http://www.ncbi.nlm.nih.gov/pubmed/21770952). 2011. Immunological Detection of N-formylkynurenine in Porphyrin-Mediated Photooxided Lens α-crystallin. Photochem Photobiol; doi: 10.1111/j.1751-1097.2011.00979.x. [Online 19 July 2011].
Roberts JE(http://www.ncbi.nlm.nih.gov/pubmed/21617534). 2011. Ultraviolet radiation as a risk factor for cataract and macular degeneration. Eye Contact Lens 37(4):246-249.
Wielgus AR, Chignell CF, Ceger P, Roberts JE(http://www.ncbi.nlm.nih.gov/pubmed/20497365). 2010. Comparison of A2E cytotoxicity and phototoxicity with all-trans-retinal in human retinal pigment epithelial cells. Photochem Photobiol 86(4):781-791.
Wielgus AR, Collier RJ, Martin E, Lih FB, Tomer KB, Chignell CF, Roberts JE(http://www.ncbi.nlm.nih.gov/pubmed/20922251). 2010. Blue light induced A2E oxidation in rat eyes - experimental animal model of dry AMD. Photochem Photobiol 9(11):1505-1512.
(Ian Thomas is a public affairs specialist in the NIEHS Office of Communications and Public Liaison.)
Roberts suggests that the following antioxidants may help prevent ocular disease.
- Lutein - 6mg
- Vitamin C - 500mg
- Vitamin E - 400IU
- Zinc - 15mg
- Copper - 2mg
- Omega-3 Fatty Acid - 500mg