Microbiological assessment of intraocular lenses beyond their expiration dates

Abstract

AimOphthalmic surgeons prefer not to use expired intraocular lenses (IOL) in routine surgery mainly because of the feared risk of intraocular infection due to microbiologically contaminated IOL. In this pilot study, we aimed to evaluate the microbiological contamination of IOL in their packages with expired dates.MethodsThis was a cross-over study in a university setting. Twenty-four IOL samples beyond their expiration dates, from four different manufacturers, were included in the current study. Swab samples were taken from the inner surface of the outer pouches and the surface of the outer box of the IOL. The IOL itself was inoculated directly to thioglycollate broth. The fluids containing the IOL were inoculated into BACTEC aerobic and anaerobic blood culture vials. All culture vials were sub-cultured and smears from all culture vials were stained by Gram’s stain. Following the incubation period, during which growth was obtained on culture plates and blood culture vials, the colonies were identified by species based on colony morphology, Gram staining, and assimilation features using the BBL Crystal Gram-positive Identification Kit (Becton Dickinson, USA).ResultsStaphylococcus epidermidis, capitis, and aureus were identified in the inner surface of the outer pouches of the packages in 4 IOL. Staphylococcus epidermidis was identified in the outer surface of the box of one IOL.ConclusionOnly 4 of the 24 IOL packages beyond their expiration dates were contaminated microbiologically. There was no contamination on the IOLs themselves. The results suggest an unrealistic fear of ophthalmic surgeons for intraocular infection with the use of an expired IOL. Further studies including chemical and physical stability, infrared and ultraviolet spectroscopy, nuclear magnetic resonance spectroscopy, refractive index, elemental analysis, surface microscopy, and biocompatibility may identify what changes might take place in expired IOL besides microbiological contamination.

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