WEARING contact lenses can give you infections that can threaten your
sight鈥攅ven if you follow the manufacturer鈥檚 cleaning instructions to the
letter. The finding suggests it is safer to wear disposable lenses that are worn
only once.
Antonio Pinna of the University of Sassari in Sardinia and his colleagues
isolated Bacillus cereus鈥攁 relative of anthrax that causes food
poisoning鈥攆rom a patient鈥檚 infected eye. The DNA of these bacteria matched
that of others found in the patient鈥檚 lens case, strong evidence that the case
was the source of the infection.
Eye infections are often the result of people not cleaning their lenses
properly if at all, according to Melanie Corbett, a consultant ophthalmic
surgeon at London鈥檚 Western Eye Hospital. But in this case, Pinna鈥檚 team found
that the lens cleaning solution failed to kill the bacterium, even when they
followed the manufacturer鈥檚 guidelines exactly.
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Judith Morris of the College of Optometrists says cleaning fluids can鈥檛 be
expected to kill absolutely every species of bug, or they would be impractical
to use. In many cases they only target certain bacteria or protozoans, she
says.
Fortunately, B. cereus seldom causes eye infections, but other
bacterial infections are relatively common. Corbett says that she sees two or
three cases every week. 鈥淐ontact lenses are a major risk factor,鈥� she says.
Pinna鈥檚 finding strengthens the case for using disposable contact lenses that
come ready sterilised and never need to be cleaned. However, wearing any foreign
body on the eye makes infections more likely, Morris warns.
Most eye infections can easily be cleared up with antibiotics, but even with
treatment there is a risk of damage to the cornea, the transparent outer layer
at the front of the eye that is responsible for about two-thirds of your eye鈥檚
focusing power. The consequences can be serious. 鈥淪ometimes the cornea is so
scarred that the patient鈥檚 vision is seriously impaired,鈥� Corbett says, 鈥渇or
example, not being able to see the top letter on the eye chart.鈥�
More at: Ophthalmology (vol 108, p 1830)