Something New Under the Sun . . . Eye Cancer
A new potential danger for sun worshipers--eye cancer--has been identified by medical researchers. And they urge people in southern climates who spend a great deal of time outdoors to wear hats, visors and good quality sunglasses that cut out at least 99% of ultraviolet rays.
While the cancer involved--called intraocular melanoma--is a rare type and the association with sun exposure not completely confirmed, several experts cautioned that the new findings underscore again how easy it may be to get too much of a good thing.
Although blindness from eye cancer is increasingly preventable, the risk of vision loss has not disappeared. Sunlamps, moreover, appear to be as much of a risk as natural sunlight. The new research findings are reported in today’s issue of the New England Journal of Medicine.
People with brown eyes seem to be accorded extra protection against intraocular melanoma, as well as blacks and other dark-skinned ethnic groups.
Blue-eyed people have greater risk. But there is disagreement among experts about whether people with fair complexions and light-colored hair have a greater chance of being affected.
Intraocular melanoma is a close relative of the skin cancer also called melanoma that has long been linked to excess sun exposure. In fact, a top Los Angeles expert noted that another unknown is whether intraocular melanoma is directly related to sunlight entering the eye or whether it is an offshoot of too much sun on the skin.
The scientists who did the new research--along with other experts--also called for a wider national study of the eye cancer situation. The new conclusions about eye cancer, however, appeared to be in concert with earlier research that established an apparent link between sun exposure and cataracts.
Fortunately, experts at three different centers in the United States and Canada noted, intraocular melanoma is far less common than melanoma of the skin. In the United States, about eight cases of eye melanoma occur each year for every million people, or about 2,000 cases. That is only about 10% the number who develop skin melanoma.
Within the last decade, moreover, treatment techniques for the eye variety have been greatly improved and five-year survival rates are now more than 80%--with the vision in the affected eye often preserved. Surgery is still used in many cases, but cancer experts have developed a technique recently in which a small piece of radioactive material is sewn temporarily on the eye surface nearest the tumor. The resulting radiation bombardment is often able to cure the tumor without destroying vision.
When intraocular melanoma spreads, it can affect the lungs, brain and liver. It is most treatable when it is detected very early in a routine eye exam because by the time the tumor has grown to a size where it affects sight, the disease is usually quite advanced.
The new findings about intraocular melanoma and sun exposure are being reported today in a study by scientists at the federal government’s National Cancer Institute in Bethesda, Md., and at the Wills Eye Hospital in Philadelphia, Pa. Their observations are based on a study of 444 people who contracted eye cancer and a similar number of others who did not have the disease but were undergoing treatment for other eye disorders.
Words of Caution
In an editorial in the journal, two Boston experts in skin melanoma urged caution in interpreting the new results. The two doctors said much remains to be discovered about the actions of ultraviolet light. However, the editorial agreed that sunlight and ultraviolet factor remains “an interesting possibility.”
Contradicting earlier findings by researchers in Vancouver, the NCI-Wills Eye team--led by Dr. Margaret Tucker, a government expert--found an association with eye melanoma risk and exposure to the sun in southern climates. In a telephone interview, Tucker said that while the new study focused on people living in the Southeast United States, the important determiner of risk appears to be the latitude at which people reside.
People with sun exposure were found to be twice as likely to have eye cancer as those who avoided the sun. Living at a southern latitude upped the risk factor to 2.7 times normal.
The “southern” factor would apply, Tucker said, to anyone living below a line stretching from Mendocino County all the way to Philadelphia. The risk zone includes most of California starting about 100 miles north of San Francisco and such places as Denver, Las Vegas, Wichita, St. Louis and Cincinnati, as well as all of Arizona, New Mexico, Texas, Oklahoma and all of the states below the Mason-Dixon line.
Eye melanoma usually manifests itself in people 60 or over, Tucker said, underscoring the potential importance of minimizing one’s sun exposure in youth. Especially because there is still some controversy over the precise role of sunlight in eye cancer, Tucker said it would be prudent for anyone who spends a great deal of time in the sun to wear effective eye protection.
Tucker noted that National Cancer Institute researchers in recent years have uniformly started protecting themselves with sun block on their skin because of the risk of skin melanoma. She urged prudence in attention to the eyes, too.
Dr. Bradley Straatsma, director of UCLA’s Jules Stein Eye Institute, said that controversy remains over the role of sun exposure in eye melanoma, with other studies attributing most of the risk to hair color, blue eyes and other cosmetic attributes of Northern European ancestry.
Though Straatsma had not yet seen the new research report, he said studies before the new one had established that “as far as sunlight (goes), the evidence so far has not been as convincing and conclusive as one might expect--because one would expect predisposition.” While Straatsma acknowledged the controversy over sun and eye cancer, he said it is still prudent for everyone to take care to avoid unnecessarily intense sunlight entering the eye. He said that most ultraviolet light rays are unrelated to clarity of vision and introduce enormous amounts of energy into the eye without adding to acuity.
Unfortunately, he said, there is no common grading system for sunglasses so consumers can make informed decisions about effectiveness. However, Straatsma said, many brands come with pamphlets that disclose some details of their ultraviolet filtration. He said glasses should be worn that bar entry to the eye of at least 99% of ultraviolet rays of wavelengths below 400 nanometers--the conventional measuring scale for such light.
In Vancouver, Dr. Richard Gallagher of the Cancer Control Agency of British Columbia, observed that the new American findings directly contradict some conclusions about eye melanoma reached by the Western Canada Melanoma Study, which published its results earlier this year. The Canadian study confirmed the link of eye cancer risk to eye and hair color but found sun exposure apparently unrelated.
A Special Risk
In a telephone interview, however, Gallagher noted that, since all of the research subjects in the Vancouver research were Canadians, the research did not involve anyone living in latitudes the American researchers now think may pose a special risk. He also noted that Canada lacks the ethnic diversity of the United States and that Western Canada’s primarily fair-skinned, fair-haired population may have influenced the findings there.
Gallagher also said that because the incidence of eye melanoma--and hence the risk of contracting it--is quite small, the Canadian research, which involved only 65 subjects in four provinces, may simply have missed the sun link.
