Wearers of disposable contact lenses found to run higher risk of infection

November 13, 1992|By Jonathan Bor | Jonathan Bor,Staff Writer

Designed to promote safety, disposable contact lenses may actually expose consumers to an increased risk of developing an infection that produces potentially blinding ulcers on the eye's clear covering.

Two studies, including one based at the Johns Hopkins University's Wilmer Eye Institute, found that people wearing disposable lenses -- soft contacts that should be discarded after a week of continuous use -- faced a far greater risk than people using other types of lenses.

But scientists conducting the studies cautioned that the problem might not be the lenses. People may be using them improperly -- wearing them too long or giving their eyes a night's rest without properly disinfecting the lenses, they said.

"There is no smoking gun or guilty party," said Dr. Oliver Schein, a cornea specialist at Wilmer. "It's important to make the point that the overwhelming majority of contact lens users never have problems. But unfortunately, the greater the convenience, the greater the risk."

He added, "The real issue raised by the study is whether it's worth the risk of discomfort, the expense of medical treatment and the possible loss of vision for the convenience of using disposable contact lenses."

The disease, called ulcerative keratitis, usually responds well to antibiotic drops but often leaves scars on the cornea when it heals. It may cause no lasting disability, but deep scars in front of the pupil can permanently blur vision. In such cases, a cornea transplant may be necessary.

Separate studies centered at the Wilmer Eye Institute and the Moorfields Eye Hospital of London found that disposable lenses were associated with the greatest risk.

The Wilmer study found the risk was heightened dramatically: The disposable lenses were 14 times as risky as were soft, "daily wear" contacts, lenses that are supposed to be taken out and cleaned every night. Soft, extended-wear lenses that are designed to be removed, cleaned and placed back in the eye every week posed twice the risk.

Rigid lenses posed the smallest risk, accounting for the fewest cases of ulcerative keratitis.

Although the studies are being published in next Sunday's Annals of Ophthalmology, early release of the findings created a stir yesterday in industry circles and among doctors gathering in a national meeting of the American Academy of Ophthalmology in Dallas.

"What the study doesn't really address -- the key issue -- is how many nights people are wearing disposable lenses and whether they are taking care of the lenses as they should be," said Dr. William Mathers, an ophthalmologist from the University of Iowa who is a member of the Contact Lens Council, an industry group.

Unveiled in the late 1980s, the disposable lenses are worn by an estimated 10 percent of the 24 million people wearing contacts. But they are gaining in popularity faster than any other type.

Extended-wear contacts made out of a soft, pliable plastic appeared on the market in the early 1980s. At first, consumers were advised to wear them for a month before removing, washing and leaving them in a disinfectant bath overnight.

The Food and Drug Administration later recommended the lenses be removed and cleaned at weekly intervals because of studies showing that users suffered disproportionately from corneal ulcers.

In the late 1980s, several manufacturers marketed the disposable contacts, extended-wear lenses that are meant to be worn continuously for a week and then thrown out.

In theory, they offered a margin of safety because they don'require cleaning and disinfecting -- provided they are never removed and put back in the eye.

Today, daytime soft lenses remain the most popular contacts -- occupying about 60 percent of the market. Soft, extended-wear contacts and the disposable versions each have about a 10 percent market share. Rigid lenses are worn by the remaining 20 percent of users.

Because of the increasing popularity of disposable contacts, scientists at Wilmer wanted to assess their safety. Their study was based on an analysis of 42 cases of ulcerative keratitis seen at a private practice in Grand Rapids, Mich., before January of this year.

Doctors appear to be in general agreement that overnight use brings an increased risk of infection. A contact lens and a closed eyelid pose two barriers to oxygen, an important part of the eye's natural defense mechanism against infection.

Previous studies have shown that among users of extended-wear lenses, one in 500 will develop ulcerative keratitis in a year.

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