Microbiologic evaluation of frequent-replacement soft contact lenses

This article reports a microbiologic study of two kinds of monthly frequent-replacement daily wear soft contact lenses, with different amounts of water content, in asymptomatic contact lens wearers.

We studied 35 lenses of 18 patients who wear frequent-replacement soft contact lenses with a water content of 38% and 40 lenses of 20 patients using frequent-replacement contact lenses with a water content of 55%. The lenses worn by patients regularly for 1 month were removed from their eyes in a sterile manner on the 30th day and were studied microbiologically to isolate pathogenic agents.

In the group of monthly frequent-replacement soft contact lenses with a water content of 38%, microorganisms were isolated at a rate of 91%; and in the group of monthly frequent-replacement soft contact lenses with a water content of 55%, microorganisms were isolated at a rate of 85%. When the two groups were compared, there was no statistically significant difference (P=0.31). Although coagulase-negative staphylococci, Corynebacterium spp, and gram-negative rods were detected in both groups, Staphylococcus aureus, non-hemolytic streptococci, Neisseriae spp, and Penicillium spp also were isolated in the group with the higher water content.

Bacteria spreading from the environment or from skin flora to the eyes showed more diversity in the group of frequent-replacement soft contact lenses with a high water content. Additionally, Penicillium spp also was isolated in this group. Therefore scrupulous attention to daily lens care is crucial for people who wear frequent-replacement soft contact lenses.