Kenneth Blomme, a 27-year-old mushroom farmer in Surrey, B.C., used ultra-thin contact lenses for five years and found them so convenient that he was often unaware that he was wearing them. He routinely left the Extended Wear Lenses (EWLS) in his eyes for up to two
weeks at a time before removing them for disinfection. But last February Blomme began to experience problems: his eyes became red and sore and easily hurt by light, and he noticed that his vision was deteriorating. Finally, after a week of pain, he made an appointment with an optometrist who
swiftly discovered that there was a serious infection, scar tissue and excess blood vessel growth in Blomme’s right eye—and irritated tissue in the left. Blomme’s problems are shared by many of Canada’s estimated 500,000 EWL users. Declared his optometrist, Dr. John Jantzi: “What we should be concerned about is what your eyes are going to look like 20 or 30 years from now. We don’t know what long-term damage is being done.”
Indeed, many ophthalmologists (surgeons who treat eye disorders) now doubt the stated advantage of EWLs: in contrast to regular contact lenses, which must be removed each night, EWLS offer weeks of carefree, uninterrupted wear. When EWLs first became available in Canada in 1977, manufacturers announced that they had created a lens so thin and porous that the eye could absorb enough oxygen through it to allow insertion for up to 30 days. In fact, giant Toronto-based Bausch & Lomb Canada Inc. advertised a “Thirty-day Lens.” Although manufacturers’ tests have proven that the lenses allow an ample flow of oxygen to the eye, the amount may be insufficient in some wearers to allow the eye to “breathe” if the lenses are worn for long periods. The length of time a patient may leave EWLs in varies from person to person and is virtually impossible to predict, necessitating regular medical monitoring. As a result, some eye doctors recommend that certain wearers take the lenses out when they go to bed. Still others prescribe removing them every week or so for a thorough cleaning. Said Dr. Murchison Callender, associate professor at the department of optometry at Ontario’s University of Waterloo: “Would you leave your socks on for 30 days?”
Still, EWLs contain many more pores than the popular “soft” plastic contact lenses first introduced in the early 1970s. Those lenses in turn adapt to the shape of the eye more comfortably than their forerunners, the hard plastic lenses of the 1950s. And since CooperVision Inc. of Markham, Ont., introduced its Permalens nine years ago, the federal ministry of health and welfare has issued 22 other licences to manufacturers for similar types of lenses—which cost up to $500 a pair. However, one Toronto ophthalmologist, requesting anonymity, declared: “I just won’t fit them. Why leave something in your eye overnight when it takes you a few minutes to take it out?”
Most problems associated with EWLS occur in the cornea, a clear lens which refracts light and allows the organ to form images at the back of the eye. Neovascularization, the growth of tiny blood vessels which can cloud the vi-
sion, is a serious problem associated with prolonged periods of contact-lens wear. It occurs when an eye, covered by a contact lens for weeks at a time, can no longer obtain enough energy from airborne oxygen. As a result, the eye seeks alternate energy sources, breaking down carbohydrates in its own tissue. That process stimulates the growth of capillaries.
But those newly formed blood vessels stop growing when a wearer removes a lens—an action which allows the blood to drain from the area and usually restores clear vision. But if the condition continues unchecked and spreads to the pupil, it may threaten the user’s sight. And although ophthalmologists have detected neovascularization in wearers of soft contact lenses, they say that it is far more likely to afflict EWL users because those lenses provide fewer chances for the cornea to return to normal.
Similarly, EWLs increase swelling of the cornea at night—a normal process which occurs because the eyelids cut in half the flow of oxygen which the sleeping wearer’s eye receives during the day. As well, the eye’s natural secretions of moisture have no chance to dissipate under EWLs and form pockets of fluid called microcysts. And protein deposits on lenses and lack of oxygen foster the development of tiny cracks in the surface of the cornea, which become breeding grounds for bacteria. The result may be ulcers, which can quickly cause a permanent loss of vision.
Although ophthalmologists stress that routine checkups are the only way to detect problems, even regular examinations are unlikely to detect polymegathism, a swelling which affects the pumping action of vital cells needed to remove excess water from the cornea. Those cells lose some of their efficiency as the eye ages, but researchers suspect that long periods of contact lens wear may accelerate the process. In Canada, only specialized university clinics have the advanced equipment needed to measure polymegathism. Declared Halifax ophthalmologist Dr. John Quigley: “We may see a lot of people 15 years down the road who need corneal transplants because of potential EWL damage.”
As concern grows over careless use of EWLs, the U.S. Food and Drug Administration is preparing an EWL survey—but the findings will not be available before 1987. At the same time, manufacturers are conducting tests on a hard EWL made of a special gas-permeable plastic which would increase the flow of oxygen to the eye. But in the meantime, EWL wearers should temper convenience with caution.
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