Contact Lenses: Picking the Right Ones

by Food and Drug Administration (FDA)

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.

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.

Shaping Up

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.

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."

Safety Concerns

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.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.