The new generation of contact lenses (search) carries a lower risk of severe eye infections when worn for extended periods of time, say British researchers.
“Those who choose to sleep in lenses should be advised to wear silicone hydrogel lenses (search), which carry a five times decreased risk of severe keratitis [eye infection] for extended wear, compared with hydrogel lenses,” they write.
Still, it’s best to remove contact lenses before sleeping, say the scientists. That significantly cuts the likelihood of developing a severe eye infection, they found.
The news comes from England’s Royal Eye Hospital in Manchester. A total of 415 contact lens wearers came to the hospital from January 2003-2004.
Most patients didn’t have eye infections. However, 80 had non-severe eye infections, and another 38 had severe eye infections.
Four types of lenses were studied: rigid, hydrogel, hydrogel daily disposable, and silicone hydrogel lenses. The difference in contact lens has to do with how much oxygen can diffuse through the lens to the cornea.
Participants were asked what kind of contacts they wore and whether they removed their contacts before sleeping. Their eyes were also screened for infection.
During waking hours, lens type didn’t make a difference in severe eye infections. It was what happened at night that mattered. Bacteria can get into the eye and wearing a contact lens for an extended period of time can help organism thrive under the lens, causing the potential for serious infections.
Sleeping in contact lenses of any kind made severe eye infections more likely. But the risk was five times lower with newer silicone hydrogel lenses compared with ordinary hydrogel lenses.
Eighteen out of 80 people with milder eye infections wore their contact lenses while sleeping. A bigger proportion — nine out of 38 people with severe eye infections — left their contact lenses in while sleeping.
Why the difference? It could be because silicone hydrogel lenses let more oxygen reach the eye, write the researchers, who included Philip Morgan of the University of Manchester’s optometry department.
One mild case and two severe cases of eye infection were seen in patients who didn’t follow recommended lens use. They admitted wearing their hydrogel daily disposable lenses on an “extended wear” (overnight) basis.
The study appears in the April issue of the British Journal of Ophthalmology.
SOURCES: Morgan, P. British Journal of Ophthalmology, April 2005; vol 89: pp 430-436. News release, BMJ Specialist Journals.