Materia Medica Malaysiana

May 7, 2007

Parasitic problems lurking behind contact lenses

Filed under: Uncategorized — malaysianmedicine @ 9:02 am

NST: KUALA LUMPUR: Contact lens users beware. There may be parasites lurking behind your image-enhancing eyewear.
If you are careless in your cleansing regime, you are opening yourself up to potential corneal inflammation.
A less-than-adequate cleaning of your contact lens allows one-cell microscopic aquatic parasites to invade the cornea and lead to acanthamoeba keratitis, or corneal ulcer acanthamoeba.
It is a rare, but very painful and potentially blinding, infection of the cornea, the transparent covering of the eye.
The infection rate is approximately one in 30,000 contact lens wearers.
In about 85 per cent of such cases, the condition is associated with contact lens use.
Symptoms of the infection include a sensation of having something in the eye, watery eyes, blurred vision, light sensitivity, swelling of the upper eyelid and extreme pain.
If the disease is detected early, when only the surface layer of the cornea is infected, it may respond rapidly to treatment.
However, if it is recognised late, intensive treatment may be needed for up to 12 months. Infection can also reoccur after treatment.

In a poster presentation on Contamination of Used Contact Lenses by Acanthamoeba species, carried out by Putri Noradyani MH, et al, from Universiti Kebangsaan Ma-laysia, on 99 lens users with no symptoms, it was found that:
# the acanthamoeba parasite is ubiquitous in various lens wearer environment. Contamination was possible from air, dust, unclean hands and use of tap water.
(Acanthamoeba is also found in chlorinated swimming pools, hot tubs and even in bottled water. It is also present, without causing infection, in the nasal passages of healthy people.)
# contact lens storage cases washed in tap water and kept wet, serve as a suitable condition for the growth of bacteria and fungus, thus becoming a food source for the parasite; and,
# a few studies have shown the adherence of acanthamoeba trophozoites (feeding stage) on the surface of new and worn contact lenses, especially in water contact lenses which are popular now.

Many contact lens users are known to ignore the advice of their optician and lens care instructions.
They rinse their lenses or storage cases in tap water, which may introduce the parasite to the case.
Once inside the case, it can survive and grow, feeding on bacteria that may also contaminate the case. The organisms are then transferred from the case to the cornea on the contact lens.
The lens holds the organisms in place on the eye, and this may ultimately lead to infection.

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