New Contacts, Old Infections. Warning for extended wear contacts!

acemanvx@yahoo.com · medicine forum Guru Joined: 15 Nov 2005 Posts: 732

The newest extended-wear contact lenses have a similar risk of eye
infections as older soft lenses worn for fewer nights.

That news is reported in Ophthalmology. It comes from postmarketing
studies funded by CIBA Vision, which makes the silicone hydrogel
lenses, marketed as Night & Day.

The researchers included Oliver Schein, MD, MPH, of Johns Hopkins
University's medical school.

Lenses' History

The FDA approved the silicone hydrogel lenses in 2001 for continuous
wear for up to 30 nights.

Older generations of extended-wear contacts had been associated with
rare cases of vision loss and eye infections. That prompted the FDA's
1989 decision to cut extended wear to seven days.

Years later, silicone hydrogel lenses were developed. Compared with
older lenses, they allow four times as much oxygen to reach the eye.
Better oxygen flow was seen as a way to possibly lower infection risk
in the eye's cornea.

The FDA ordered postmarketing studies of silicone hydrogel lenses to
check corneal infection rates.

Year-Long Study

The study included 6,245 people who had been given prescriptions for
the silicone hydrogel lenses. Most (80%) wore their lenses nonstop for
at least three weeks.

During the year-long study, few participants had corneal infections.
Two had corneal infections that led to vision loss. Eight others had
corneal infections that didn't cause vision loss.

Overall, the yearly rate of corneal infections was 18 per 10,000
people, the study shows.

That's similar to rates previously reported for conventional,
extended-wear soft lenses worn for fewer consecutive nights, according
to the researchers.

Researchers' Pecking Order

Schein's team calls contact lenses "very safe" in general, though
they note that contact lenses are associated with some extra risks,
compared with eyeglasses.

They rank the risk of vision loss from eye infection for different
types of contact lenses:

Lowest risk: Rigid, gas-permeable contact lenses for daily wear

Next-to-lowest risk: Soft contact lenses for daily wear

Highest risk: Silicone hydrogel contact lenses for extended wear of
three-to-four weeks

However, they're not calling silicone hydrogel lenses dangerous. The
odds appear "reasonable," write the researchers, for people who
understand the risks and want to wear their contacts around the clock.

The study notes that one researcher is a CIBA Vision consultant and one
is a CIBA Vision employee.

SOURCES: Schein, O. Ophthalmology, Dec. 2005; vol 112: pp 2172-2179.
News release, Johns Hopkins University.

By Miranda Hitti
Reviewed by Louise Chang, MD
© 2005, WebMD Inc. All rights reserved.

Dr. Leukoma · medicine forum Guru Joined: 30 Apr 2005 Posts: 1283

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