By Dirk Mathison
Updated November 06, 1989 12:00 PM

The invention of contact lenses liberated millions of nearsighted people from the inconvenience of glasses. In 1980, “extended-wear” lenses became available, enabling people to leave their contacts in place day and night for up to a month. But those who are sleeping in their lenses are sleeping less easily now. Two studies in last month’s New England Journal of Medicine assert that the 4 million users of extended-wear lenses are 10 to 15 times more likely to develop a condition called ulcerative keratitis than those who remove their lenses each night. Dr. Oliver Schein, 34, an ophthalmologist at the Massachusetts Eye and Ear Infirmary and one of the authors of the studies, discussed the troubling findings with Boston bureau chief Dirk Mathison.

Why are extended-wear lenses more dangerous than daily-wear lenses?

It is felt that when your eyes are open and blinking, tear and oxygen exchange enable the cornea to receive the nutrients it needs to stay healthy. People who wear the lenses overnight run an increased risk of developing ulcerative keratitis because the added lens barrier inhibits this process. The cornea is made up of several layers, and the thin surface on which the lens rests is called the epithelium. It’s smooth and lustrous, but a lens can cause an abrasion on it. As soon as you have a defect on the cornea’s surface, either through a mechanical action or lack of nutrients, microbes can set up shop and cause an infection. Ulcerative keratitis, which can be extremely painful, means there’s an ulceration and inflammation of the cornea.

What are the odds of contracting ulcerative keratitis?

Roughly one in 500 extended-wear lens users will contract the disease every year. The studies show that of the 4 million users of extended-wear lenses, about 8,000 people per year will contract ulcerative keratitis. Of those, perhaps one in 20 may require a corneal transplantation to restore vision. The risks increase incrementally for every day contacts are worn without removal.

Does the same danger apply to people who occasionally sleep in other kinds of contact lenses?

We found that a large number of people who are users of daily-wear lenses sleep in them overnight and that those people increase their risk of getting the disease ninefold.

What are the early symptoms of ulcerative keratitis?

Pain and redness, with some decrease in vision. Those symptoms should alert the wearer to remove the lenses and seek prompt consultation.

How is the infection treated?

We usually prescribe antibiotic drops initially. Severe cases may require hospitalization for more intensive antibiotic treatment. The earlier you catch it, the better off you are.

What can happen if the condition goes unchecked?

The ulceration will increase in size so that the scarring, which can occur even after successful treatment, may affect vision. In the worst case scenario, the ulcer can perforate the cornea and allow leaking of the interior contents. In a situation where there is a perforation or extensive scarring, a corneal transplantation may be required.

Can lens hygiene prevent infection?

Bacteria come from the outside, but whether they come from the lens case, the lens itself or your hand, we’re just not sure. Even people who don’t develop this condition may be using contaminated products. There’s some importance to hygiene, but it is dwarfed by the problems caused by overnight wear.

Do people care for lenses improperly?

I’m not sure there’s any blame to be laid here, although there’s room for improvement. Practitioners can better explain the risks; the industry can improve labeling directions, and consumers should take the instructions seriously.

Should studies like this have been done before contacts were marketed in 1980?

The FDA has very strict criteria for approval of medical devices, including contact lenses. Initial studies indicated some risk for extended use, but the level of risk was felt to be acceptable. Besides, there are always differences between an experimental study and how people behave in real life.

Should people stop using extended-wear lenses?

Not necessarily. However, practitioners and patients should realize there is a price to pay for the convenience, and that price is an increased risk. If you do wear them, I would recommend limiting overnight wear and increasing the frequency of hygiene as much as possible. For the overwhelming majority of users, contacts are safe. But I think there will always be some risk involved in their use. In the long term, it’s going to take an attitude change—people must realize that these products aren’t cosmetics or pieces of clothing but medical devices.