Infection a risk with preservative-free drops
Cordelia Molloy/Science Photo Library
Traditional glass dropper bottles are at risk of microbial contamination |
Some patients using preservative-free eye drops in multiple-use containers
could be at risk of serious eye infection due to microbial contamination
of the product, according to the authors of a new study (British
Journal of Ophthalmology 2006;90:139). They found the overall
incidence of contamination in used preservative-free bottles to be
8.4 per cent
(95 per cent confidence
interval 3.71–15.9).
Preservative-free eye drops can be ordered from specials manufacturers
and come in traditional glass containers for use over a number of days.
The authors explain that these specials are given arbitrary expiry dates
based on practical considerations and that the generally accepted timeframe
for use is three days in an inpatient setting and up to seven days in
an outpatient setting.
The investigators collected 95 used eye drop bottles at day three (inpatients)
and day seven (outpatients), and the drops were cultured for microbial
growth. Four per cent of bottles collected from inpatients were contaminated
compared with 25 per cent of outpatient bottles — a statistically
significant difference (P<0.01). Of the 53 eye drop bottles containing
antibiotics, none showed any microbial contamination. Contaminated bottles
contained acetylcysteine, prednisolone or hypromellose as active ingredients.
Several of the contaminated bottles grew more than one type of organism.
The most commonly isolated organism was Staphylococcus aureus, with an
occurrence of 4.5 per cent.
The authors state the design of multiple-dose eye drop containers, spillage
of contents and poor patient administration technique as possible causes
of contamination. Many patients experience allergy or irritation from
preservatives in eye drops, but are unable to use single-dose-unit eye
drops because they are either unavailable or prohibitively expensive.
Furthermore, patients with compromised ocular surface defences may be
at risk of serious eye infections, say the authors.
The authors suggest that doctors exercise caution when prescribing multiple-use
eye drops without preservative in patients at high risk of infection. |
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