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Contact lens cleaners may not kill all germs
Some contact-lens solutions may fail to destroy parasites that can cause dangerous eye ulcers, a study warns.
Some contact-lens solutions may fail to destroy parasites that can cause dangerous eye ulcers, a study warns.
The Clinical Institute of Hygiene in Vienna, Austria, tested three types of widely-sold cleaners for their ability to destroy several strains of Acanthamoeba, a single-celled parasite that is a major source of eye infection among contact-lens wearers.
All three cleaners killed the creature in its trophozoite, or non-reproductive, stage but their performance in destroying it at the cyst, or egg, phase varied a lot.
The best performer by far was a two-step cleaner (Titmus H2O2, made by the US firm Ciba Vision Corp.) that comprises a 0.6 percent hydrogen peroxide solution in which the lenses are left to soak for eight hours.
The hydrogen peroxide is then tipped out and the lenses neutralised by a second solution for 10 minutes before they are inserted.
The product killed virtually all cysts, some of them just after 30 minutes.
Runner-up was a multipurpose solution (Meni Care Plus, made by Menicon Pharma of Germany) which killed the cysts of one out of the three strains.
The least effective, the researchers said, was a one-step cleaner (Oxysept Comfort, made by Pharm Allergan of Germany), in which a neutralising tablet is added at the same time as a three-percent hydrogen peroxide solution.
Even when the lenses were left to soak for eight hours, the Oxysept Comfort still left viable cysts of all three parasite strains, the authors say.
They suggest that the neutralisation technique may be so quick that the bugs are not effectively destroyed.
Acanthamoeba are a potential source of corneal ulcers, a painful condition that can cause deterioration of vision or even blindness.
The introduction of long-wear soft contact-lenses in the 1980s, triggered an epidemic of these infections, usually among wearers who failed to observe the hygiene regimen.
The researchers suggest that, in any case, contact-lens users take additional steps to clean their storage case by microwave or by boiling.
The study is published in the British Journal of Ophthalmology, a specialist publication of the British Medical Association (BMA). Bureau Report
The Clinical Institute of Hygiene in Vienna, Austria, tested three types of widely-sold cleaners for their ability to destroy several strains of Acanthamoeba, a single-celled parasite that is a major source of eye infection among contact-lens wearers.
All three cleaners killed the creature in its trophozoite, or non-reproductive, stage but their performance in destroying it at the cyst, or egg, phase varied a lot.
The best performer by far was a two-step cleaner (Titmus H2O2, made by the US firm Ciba Vision Corp.) that comprises a 0.6 percent hydrogen peroxide solution in which the lenses are left to soak for eight hours.
The hydrogen peroxide is then tipped out and the lenses neutralised by a second solution for 10 minutes before they are inserted.
The product killed virtually all cysts, some of them just after 30 minutes.
Runner-up was a multipurpose solution (Meni Care Plus, made by Menicon Pharma of Germany) which killed the cysts of one out of the three strains.
The least effective, the researchers said, was a one-step cleaner (Oxysept Comfort, made by Pharm Allergan of Germany), in which a neutralising tablet is added at the same time as a three-percent hydrogen peroxide solution.
Even when the lenses were left to soak for eight hours, the Oxysept Comfort still left viable cysts of all three parasite strains, the authors say.
They suggest that the neutralisation technique may be so quick that the bugs are not effectively destroyed.
Acanthamoeba are a potential source of corneal ulcers, a painful condition that can cause deterioration of vision or even blindness.
The introduction of long-wear soft contact-lenses in the 1980s, triggered an epidemic of these infections, usually among wearers who failed to observe the hygiene regimen.
The researchers suggest that, in any case, contact-lens users take additional steps to clean their storage case by microwave or by boiling.
The study is published in the British Journal of Ophthalmology, a specialist publication of the British Medical Association (BMA). Bureau Report