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by Dixie Farley
| At a Glance
| Ophthalmologists (M.D. or D.O.) are eye surgeons
who study and treat eye diseases and can also perform the duties of
| Optometrists (O.D.) examine eyes, diagnose and
treat vision problems, and prescribe eyeglasses and contact lenses. In
most states, they also can prescribe medicine.
| Opticians grind and dispense eyeglasses and in
some states dispense contact lenses.
Imagine wearing your contact lenses for a few hours and then, after you pop them out, still seeing clearly for a portion of the day. For certain individuals with nearsightedness, that image can be reality, thanks to a new lens the Food and Drug Administration recently cleared for marketing.
The OK rigid gas-permeable contact lens, made by ConTEX, Sherman Oaks, Calif., is the first lens designed to correct nearsightedness by temporarily reshaping the transparent tissue known as the cornea that covers the iris and pupil. It is just one of many choices for the 28 million Americans who wear contact lenses.
These medical devices, sold under more than 350 brand names, offer numerous options, including rigid-lens handling ease, soft-lens comfort, bifocal vision, a rainbow of colors, no-fuss disposables, and even protective help against ultraviolet radiation.
The idea behind the OK lens is not new. Since the early 1960s, some optometrists have used conventional daily-wear rigid lenses to reshape corneas. This procedure is called orthokeratology, or Ortho-K. FDA considers such treatment of an individual patient to be the practice of medicine and therefore not subject to regulation. Selling contacts not cleared for Ortho-K to practitioners for this use is illegal marketing, however, so the agency is helping manufacturers obtain clearances specifically for Ortho-K. (See "Buyer Beware.")
Studies before FDA began regulating contact lenses, in 1976, show that Ortho-K appears to be safe, says James Saviola, O.D., chief of the vitreoretinal and extraocular devices branch at FDA's Center for Devices and Radiological Health. "The lower your amount of nearsightedness, the greater your probability of success with Ortho-K," he says.
Ortho-K reshaping involves the use of a series of lenses that apply pressure to the cornea. Once the desired result is achieved, use of daily-wear maintenance lenses is crucial to retain the reshaping. If you wear the maintenance lenses faithfully, Saviola says, "you may only need to wear the lenses for a portion of the day."
However, Ortho-K does not work for everyone. Some people do not experience any significant reduction in nearsightedness. "An individual's response is difficult to predict," Saviola says. "It may take weeks or months to have an effect."
The most serious safety concern with any contact lens is related to overnight use. Extended-wear (overnight) contact lenses--rigid or soft--increase the risk of corneal ulcers, infection-caused eruptions on the cornea that can lead to blindness. Symptoms include vision changes, eye redness, eye discomfort or pain, and excessive tearing.
The risk of corneal ulcers for people who keep extended-wear lenses in overnight is 10 to 15 times greater than for those who use daily-wear lenses only while awake, says James Saviola, O.D., chief of the vitreoretinal and extraocular devices branch at FDA's Center for Devices and Radiological Health.
When the eyes are open, he explains, tears carry adequate oxygen to the cornea to keep it healthy. But during sleep, the eye produces fewer tears, causing the cornea to swell. Under the binding down of a rigid contact lens during sleep, the flow of tears and oxygen to the cornea is further reduced. This lack of oxygen leaves the eye vulnerable to infection.
Extended-wear rigid lenses also can cause unexpected, sometimes undesirable, reshaping of the cornea.
Soft extended-wear lenses also bind down on the closed eye, but they are porous and allow some tears through during sleep. Because they have so little form, their binding has little effect on the shape of the eye.
FDA has approved extended-wear lenses for use up to seven days before removal for cleaning. Still, there are risks with use of extended-wear lenses, "even if it's just one night," Saviola says. Daily-wear lenses are removed daily for cleaning and are a safer choice, provided they aren't worn during sleep.
Another sight-threatening concern is the infection Acanthamoeba keratitis, caused by improper lens care. This difficult-to-treat parasitic infection's symptoms are similar to those of corneal ulcers.
The use of homemade saline from salt tablets is one of the biggest contributors to Acanthamoeba keratitis in contact lens wearers. "FDA no longer condones the use of salt tablets, and neither should a concerned pharmacist," writes Janet Engle, Pharm.D., in the 1996 Handbook of Nonprescription Drugs. Engle is associate dean for academic affairs and clinical associate professor of pharmacy practice at the University of Illinois in Chicago.
Microorganisms may also be present in distilled water, so always use commercial sterile saline solutions to dissolve enzyme tablets. Heat disinfection is the only method effective against Acanthamoeba, and it also kills organisms in and on the lens case. (See "Proper Care Gives Safer Wear.")
Soft lenses are much more comfortable than rigid lenses, thanks to their ability to conform to the eye and absorb and hold water. You can get used to soft lenses within days, compared with several weeks for rigid. An added benefit is that soft lenses aren't as likely as rigid lenses to pop out or capture foreign material like dust underneath. Extra-thin soft lenses are available for very sensitive people.
While the ability to hold water increases oxygen permeability of soft lenses, it increases their fragility as well.
Rigid lenses generally give clearer vision. They can be marked to show which lens is for which eye. They don't rip or tear, so they're easy to handle.
Also, rigid lenses don't absorb chemicals, unlike soft lenses, which Saviola says are like sponges. "They'll suck up any residues on your hands--soap, lotion, whatever."
Both soft and rigid lenses offer bifocal correction. In some models, each lens corrects for near and distance vision. In others, one lens is for near vision, and the other is for distance. Middle-aged people who have good distance vision but need help for reading can get a monovision reading lens for one eye.
Soft lenses additionally come as disposable products (defined by FDA as used once and discarded) or as planned-replacement lenses.
With planned-replacement lenses, the practitioner works out a replacement schedule tailored to each patient's needs, says Byron Tart, director of promotion and advertising policy at FDA's devices center. "For patients who produce a higher level of protein in their eyes or don't take as good care of their lenses, it might be healthier to replace the lenses more frequently," he says.
Some practitioners prescribe disposables as planned-replacement lenses, which are removed, disinfected and reused before being discarded. Saviola cautions that lenses labeled "disposable" don't come with instructions for cleaning and disinfecting, while those labeled specifically for planned replacement do. Whatever lenses your practitioner prescribes, be sure to ask for written instructions and follow them carefully.
Very few people wear hard lenses, but they are available for people who have adapted to them and want them. Hard lenses are not the same as rigid gas-permeable lenses, since they do not allow oxygen transmission through the lens.
Contacts Not for Everyone
People with inadequate tearing (dry eye syndrome) usually can't tolerate contacts, says Donna Lochner, chief of the intraocular and corneal implants branch of FDA's devices center. In addition, Lochner says, "Severe nearsightedness often can't be corrected effectively with contact lenses."
Saviola notes that certain working conditions, such as exposure to chemical fumes, may be undesirable for contact-lens wearers. Contacts may be ruled out by allergy to lens-care products or by corneal problems, such as a history of viral infection of the cornea. "Extra caution," he says, "should be exercised with diabetics, because they're susceptible to infection and have trouble healing."
Cosmetic use of contacts is limited in children. Adolescence is the youngest age as a rule to consider contact lenses, says Saviola, but some practitioners do fit 9- to 11-year-olds. "You may prescribe for a younger child who has the motor skills and responsibility to handle contact lenses."
For some people who haven't been able to wear contacts and want to, implantable lenses may be an option in the future.
Doctors are studying ring segments, "shaped like parentheses," Lochner says, which are implanted in the cornea. "They flatten out the cornea, changing the shape to give the correct optical power." Lenses that are implanted inside the eye are also being studied to correct refractive error, she says.
Correcting vision is not the only use for contact lenses.
Some soft contacts are used as bandage lenses after photorefractive keratectomy laser surgery for nearsightedness. The surgery removes the outer cell layer of the cornea, creating a large abrasion on the eye. "It's excruciatingly painful," Saviola says, "if you don't have a protective covering on the cornea after the anesthetic wears off."
Collagen eye shields are used as bandage lenses to relieve pain from other abrasions or sores on the cornea. They dissolve in a couple of days.
Companies that sell contact lenses compete stiffly for business, offering discounts and premiums such as a second set free.
But a discount for the lenses might not save you money if the price doesn't include other needed products and services, such as a thorough eye examination, lens-care kit, and follow-up visits to make sure you're adapting. A moderate cost for a package that has everything you need may be the best deal.
Before you make an appointment, ask the practitioner these questions:
Asking questions about any new prescription treatment is always a good idea. Like medicines, contact lenses provide benefits and pose risks. But even with the increased risk of corneal ulcers posed by extended-wear lenses, Saviola says this risk alone isn't enough to say the devices aren't safe and effective if properly used.
"If people are informed," he says, "then they're making a judgment based on available information. That's the thing we always struggle with, conveying enough information to people and having the practitioner convey enough information, so that the consumer can make an informed choice."
Dixie Farley, who was on the staff of FDA Consumer for more than 13 years, retired from federal service in January.
Sorting help from hype in any media--the World Wide Web, television, or print--can pose a problem. So remember: If a claim sounds too good to be true, it probably is.
Here are some recent examples of potential problems:
The Federal Trade Commission is reconsidering whether to require that practitioners release contact lens prescriptions to patients, as is required for eyeglasses.
According to the American Optometric Association, state laws mandate this release in Alabama, Arizona, Colorado, Delaware, Florida, Georgia, Indiana, Iowa, Louisiana, Maine, Massachusetts, New Hampshire, New Jersey, New York, North Carolina, Ohio, Oregon, South Dakota, Texas, Vermont, Virginia, Washington state, and Wyoming. Some practitioners in the other states may release prescriptions upon request.
FDA Consumer magazine (March-April 1998)
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