Sleeping in contact lenses increases wearers' chances of developing potentially blinding eye infections, despite the introduction of more user-friendly, disposable lenses, according to new research.
In the first comprehensive study since throwaway lenses were launched about 10 years ago, Dutch scientists found that people who routinely slept in their contacts were 20 times more likely to develop bacterial infections in their corneas, compared with those who wore hard lenses that must be removed every night.
Even wearing soft lenses that are not disposable and removing them every night did not eliminate the infection risk. According to the study, published Friday in The Lancet, a British medical journal, wearers of soft lenses who removed them nightly still developed infections three times more frequently than those who wore the older, rigid lenses.
The study, which involved every ophthalmologist in the Netherlands who served the nation's 1.4 million contact lens wearers, reached almost exactly the same conclusions as the last major look at contact lenses and bacterial eye infections.
That study was published in 1989, when some lenses were being worn for up to a month continuously and before the advent of contacts designed to be discarded after a day or a few weeks.
The new study, led by Dr. Aize Kijlstra, a professor of experimental ophthalmology at Amsterdam University, noted that one in 500 people who slept in their lenses contracted microbial keratitis, a bacterial infection of the cornea.
About 15 percent of those people lost their sight, he said.
"On occasion, one night when you've been to a party, that's not too bad. But I wouldn't recommend sleeping in them regularly," Kijlstra said.
Dr. Oliver Schein, a professor at Johns Hopkins University's Wilmer Eye Institute who was involved in the 1989 study, said he was not surprised by the new research.
Contact lenses have changed little in the past 10 years, he said, only the way they are used. They are now removed less often and handled less often, and thrown away sooner but are still made of the same material, he noted.
"Most of the risk comes once you begin to sleep in them at all," he said.
About 80 million people worldwide now wear contact lenses.
In the United States, about 33 million people wear contact lenses. Most of the soft lenses on the market are approved by the U.S. Food and Drug Administration for continuous wear up to seven days.
Written By Emma Ross