NEW YORK (Reuters Health) - Many people underestimate the risks of contact lenses, continuing to wear them when their eyes become tired or irritated and not cleaning them as directed, according to a Florida doctor.

In the short term, these missteps can lead to sore, itchy eyes, abrasions and sometimes to potentially blinding ulcers and infections, said Dr. Thomas J. Liesegang, an ophthalmologist at the Mayo Clinic in Jacksonville, Florida.

Over time, he told Reuters Health, such practices increase the risk of permanent damage to the cornea, the transparent outer layer of the eye, including a loss of corneal cells, a thinning of the cornea and a change in the cornea's shape, referred to as warpage.

"Contact lenses have more of an effect on the cornea than most people realize," said Liesegang, who published a review of the literature on the topic in a recent issue of The CLAO Journal, a publication of the Contact Lens Association of Ophthalmologists. "In some cases, the effects can be reversible and in some they can be permanent."

What is not clear, however, is whether any of the permanent effects will cause vision problems later in life. "We don't know what the long-term effects will be," he added.

Though most contact-lens wearers don't encounter serious side effects, even those who are diligent about caring for their eyes can sometimes have problems. This can be due to reduced oxygen to the cornea that occurs upon lens insertion, leading to a build-up of carbon dioxide in the tissue, Liesegang explained. In turn, this may cause an inflammatory response marked by swelling and redness. Bacteria can become trapped under the contact lens, he added, possibly leading to infection.

The amount of oxygen deprivation depends on what the lenses are made of and how long they are worn. Hydrogel lenses worn continuously for a week at a time can especially reduce oxygen flow, Liesegang said. As a result, he usually recommends that those lenses be removed each night, since closed eyelids during sleep further reduce oxygen to the eye.

However, recently approved silicone hydrogel lenses that are intended to be worn for up to 30 days at a time allow more oxygen to the eyes and may overcome some of the problems of continuous use found with other lenses, Liesegang pointed out. But some patients may not find them quite as comfortable as lenses made solely from hydrogel, the material used in most soft lenses on the market, he noted.

Choosing which lens is best requires considering several factors, according to Liesegang. "There's no one best lens," he said, adding that what is best for one person may not be ideal for the next.

Patients should consider such factors as the comfort of each lens, when and how often they plan to wear their lenses, their commitment to keeping them clean (those who don't want to deal with solutions may opt for daily or continuous-wear disposables) and their budget (while convenient, disposables may be more expensive), Liesegang advised.

To help prevent eye problems with contact lenses, Liesegang recommends that users:

-- See their eye-care professional regularly so he or she can check for problems, even if the user feels that nothing is wrong.

-- Wear the lenses as directed.

-- Always carry a pair of glasses so that you are not forced to continue to wear contact lenses that are irritating your eyes.

-- Wash your hands before handling your lenses.

-- Clean your lenses carefully. "At least 50% of people don't clean their lenses properly," he said.

"There are millions of patients who wear contacts and most of them wear them successfully," Liesegang stated. "But these are not completely safe devices."

SOURCE: The CLAO Journal 2002;28:12-27.

Reference Source 89

For more information on how to prevent other diseases, use
PreventDisease.com's "Quick Prevention Resources".