Purpose: To determine the types of microorganisms and their frequency of isolation on the external ocular surface in children wearing soft contact lenses on a daily wear schedule.
Methods: Children aged 8 to 14 years were fitted with commercially available, soft contact lenses which were worn on a daily wear basis. The upper bulbar conjunctiva and the lower lid margins of each eye were swabbed at baseline and then at 6-monthly intervals for 2 years during lens wear. Swabs were processed, cultured and microorganisms identified using standard microbiological techniques.
Results: At baseline, 36% of the upper bulbar conjunctivae and 53% of the lower lid margins were contaminated with predominantly gram-positive bacteria. Recovery of samples with positive growth from the upper bulbar conjunctivae decreased during lens wear and ranged from 27 to 14%. The difference was statistically significant at the 12-month visit(14%, p = 0.011). The lower lid margins generally showed similar levels of contamination as at baseline except for less contamination at the 12-month visit (33%) (p = 0.05). Staphylococcus epidermidis and Propionibacterium sp. were the predominant microorganisms isolated from both the sites with and without lens wear. Gram-negative bacteria were infrequent and when isolated, the numbers of colonies were few. Fungus was isolated in a small percent (ranging from 0 to 4.8%) of eyes at various time points.
Conclusions: The external ocular surface of children is contaminated with gram-positive bacteria that are resident microbiota. During lens wear, there was a trend for lesser recovery of organisms from the upper bulbar conjunctival samples,but there was no change in the type of microorganisms isolated. At all times, lower lid margins showed consistently greater colonization and is a source of potential contamination of the conjunctival surface.