A team of researchers led by the Johns Hopkins Wilmer Eye Institute have determined that the
corneal infection rate associated with the use of 30-day -extended-wear contact
lenses made from silicone hydrogel is comparable to that previously reported for
older lens types worn for fewer consecutive 24-hour periods.
The study, published in the Dec. 1 issue of Ophthalmology, recruited 6,245
patients, 64 percent of them women with an average age of 35, from 131 practices
in North America between August 2002 and July 2003. All participants were
prescribed and fitted with CIBA Vision NIGHT & DAY silicone hydrogel soft
contact lenses, to be worn for 30 consecutive 24-hour periods. Participants
completed a baseline survey to collect information and potential risk factors
for infections. At three and 12 months after enrollment, information regarding
contact lens wearing schedules, discontinuation of lens wear and the occurrence
of red and painful eye infection requiring medical attention was obtained.
Eighty percent of the participants in the study completed 12 months of lens
wear and wore their lenses for three or more weeks continuously. The overall
annual rate of evident corneal infection was 18 per 10,000. There were two cases
of corneal infection with partial loss of vision and an additional eight cases
without vision loss. The rate of infection was lower for users wearing the
lenses for three or more weeks than for those wearing the contact lenses for
less than three-week continuous periods.
"The incidence of vision loss as a result of corneal infections among users
of the silicone hydrogel contact lens was low," said Oliver Schein, M.D., M.P.H.
lead investigator of the study and the Burton E. Grossman Professor of
Ophthalmology at the Johns Hopkins Wilmer Eye Institute. "The overall rate for
corneal infection with the wearing schedule of the silicone hydrogel soft
contact lenses for up to 30 nights was similar to that reported for conventional
(HEMA) extended-wear soft lenses worn for fewer consecutive nights," he added.
Contact lenses are safe, but have some risks not associated with glasses,
added Schein. "Daily wear rigid gas-permeable contact lenses appear to have the
lowest risk for corneal infection, followed by daily wear soft contact lenses
and seven- or 30-day-wear soft contact lenses," said Schein. "Not everyone can
wear the lenses successfully for a full 30-nights, but the risk of infection
does not appear to increase with greater number of consecutive nights of wear.
This is a different pattern than we previously observed with conventional
extended-wear soft lenses, where the risk did go up substantially with
additional overnight use."
The study also points out that there are many choices for those who do not
want to wear spectacles to correct their vision, including hard and soft
daily-wear contact lenses, and refractive surgery, such as LASIK (laser-assisted
in situ keratomileusis).