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Lens treatments can serve as prophylaxis against eye disease
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A known correlation between ultraviolet (UV) radiation and various ocular anomalies exists — while published studies have shown some discrepancies in this area, a strong link between UV radiation and cataract formation is generally acknowledged. Practitioners are now recommending UV-blocking lens treatments to help prevent ocular diseases.
UV and short-wavelength exposure
While a strong correlation has been established between UV rays and cataract formation, less evidence exists to suggest such a correlation between UV and age-related macular degeneration (AMD), according to Jan P. Bergmanson, OD, PhD, a researcher and educator at the Texas Eye Research and Technology Center in Houston.
“When it comes to UV radiation and AMD, there is no association, or at best a very weak one,” he told Primary Care Optometry News. “Some discrepancies exist among published studies, but it boils down to the fact that only 1% or less of the UV radiation on the eye is actually reaching the retina. So it is a very small quantity.”
But short-wavelength radiation has been found to cause retinal damage, Dr. Bergmanson said. “So if the intensity is strong enough from the short-wavelength blue light, it can cause damage,” he said.
However, this association does not necessarily translate into a link between short-wavelength radiation and AMD, Dr. Bergmanson added. “That has not yet been established,” he said. “I know of one study that claimed some association between AMD and exposure to short-wavelength light, but that is not firmly established.”
Dr. Bergmanson added that he is aware of no link between short-wavelength radiation and cataract formation.
Phototoxicity study
A recent study conducted by Marc Alexandre, OD, examined the long-term ocular damage of low-wavelength light. Dr. Alexandre is the international medical and professional relations general manager for Essilor. “For a long time, the effects of low-wavelength rays of light concerned me,” he said. “I read a lot of articles on the subject, and none were very clear about the long-term damages on the different parts of the eye.”
In choosing a specific population for the study, Dr. Alexandre was careful to choose a group that would yield relevant results. “I didn’t want an exotic population, as we might be criticized that the study was not relevant to European populations,” he said. “With Prof. Christian Corbé, MD, an ophthalmologist who was involved in selecting astronauts for space missions, I decided to study high mountaineering guides from the foot of Mont Blanc in Chamonix, France.”
With the help of local occupational health doctors and local ophthalmologists, Dr. Alexandre and his colleagues selected 40 guides. “These men spend most of their lives 7,000 feet above the rest of us,” Dr. Alexandre said. “Most of them are skiing instructors during the winter and spring seasons.”
The researchers also chose 40 men of the same age group who lived in the area to use as a control group. Although there were no female mountaineering guides in 1993, today, there are three women in the mountaineering group, Dr. Alexandre noted.
“To make sure we had two distinct groups, the control group not only matched the ages of the guides, but they were not amateurs regarding outdoor activities,” Dr. Alexandre said.
The researchers followed the two groups from December 1993 until December 2001. In December 2002, Dr. Alexandre presented his study results at the American Academy of Optometry meeting in San Diego.
“The study determined that ultraviolet rays create long-term damage to the retina, which relates to macular degeneration,” Dr. Alexandre said. “In summary, the eyes of the guides have aged much more quickly than the eyes of the control group,” he said. “Some retinal alterations have been noticed, which is probably the novelty of this study. A study with a much larger population will be needed to confirm our findings.”
Dr. Alexandre and his colleagues plan to follow the two groups until 2009.
Recommendations for protection
As a result of the study, the researchers determined that spectacles with lenses blocking UV light and the lower part of the spectrum are essential.
“As 15% to 20% of light reaches the eyes, spectacles with large lenses that wrap around the complete eye area of the face are best,” Dr. Alexandre said. “For high altitudes, especially glacier and snow surfaces, a ‘Glacier frame’ with side protection is absolutely needed. And because the reflection of UV light on white surfaces is 80%, the lenses must totally block UV light and visible light with brown and orange tints in order to cut off blue or even green rays of sunlight.”
Dr. Bergmanson said he finds UV filtering in spectacle lenses to be beneficial in the prophylaxis of cataracts and AMD.
“The UV400 type of lens — polycarbonate material — is good,” he said. “It is a good, safe material; it doesn’t splinter.”
According to William L. Park, OD, FAAO, of Lions Vision Research in Baltimore, UV-filtering lenses are essential to prevent ocular damage. “We used to work with the Corning CPF,” he said. “We worked with the yellow filter, the glare cutter 450x and the 500 series, which was a brown amber.”
Dr. Park said he recently tried a new lens by Bayz Sunwear based in Havre De Grace, Md., that he also found to be quite effective.
“I actually saw the president of the company at a show, and he presented lenses that were developed for the Chesapeake Bay fishermen,” he said. “And so I called him and told him I thought my patients would benefit from these lenses. He sent me a pair, which I wore for about 3 weeks. And that’s what I wear now.”
Dr. Park said he would especially recommend these lenses for patients with macular degeneration or any sort of visual impairment.
Another means of protecting the eye against damage from UV radiation is the use of UV-blocking contact lenses. “The contact lens needs to have a filter formulated into the plastic,” Dr. Bergmanson said. “The lenses that have a built-in UV filter do a good job in bringing dangerous radiation down to safe levels.”
Filters for enhanced reading
Lens filters may also show benefits in terms of enhanced reading, according to practitioners.
“A yellow filter usually gives you greater contrast, in terms of the print in the background,” Dr. Park said. “It enhances contrast and helps control glare indoors.”
Dr. Bergmanson said he has no recommendations for a filter to enhance reading, but offered advice on lighting. “I recommend that you have a good light source and that the light source be placed behind you, so that it shines onto what you are trying to read,” he said. “If you have reasonably good contrast, you are not likely to have any problems.”
For Your Information:
- Jan P. Bergmanson, OD, PhD, is an educator at the College of Optometry, University of Houston. He can be reached at 505 J. Davis Armistead Bldg., Houston, TX 77204-2020; (713) 743-1950; fax: (713) 743-2053. Dr. Bergmanson has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for the companies mentioned.
- Marc Alexandre, OD, is international medical and professional relations general manager for Essilor International. He can be reached at 13515 North Stemmons Freeway, Dallas, TX 75234; (800) ESSILOR; fax: (972) 241-8601. Dr. Alexandre is a director of Essilor International.
- William L. Park, OD, FAAO, practices at Lions Vision Research in Baltimore. He can be reached at 600 N. Wolfe Street, B1-70, Baltimore, MD 21287; (410) 955-0580; fax: (410) 817-9504; e-mail: wpark@jhmi.edu. Dr. Park has no financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.