Parasitological and microbiological assessment of contact lens storage cases: a survey of asymptomatic lens student wearers from five medical specialties in Tunisia, North Africa.

Background: Contamination of contact lenses has always been correlated with contamination of lenses and lens storage cases (LSCs), with higher loads of microorganisms in LSCs. The aim of the present study is to better understand non-compliance with strict hygiene rules in asymptomatic contact lens wearers, and to track circulating germs in LSCs that may affect the integrity of the eye.

Methods: Demographic and behavioral data were collected from 111 asymptomatic lens wearers belonging to different medical faculties in Tunisia. Seventy LSCs were subjected to microbiological investigations, by direct examination and culture, in order to identify contaminating micro-organisms. The Richness and evenness of the species encountered were assessed to measure biodiversity on a local and international scale.

Results: The study population was characterized by an average age of 22.8 ± 2.4 years and 95% female gender. Microbiological contamination accounted for 81.42% of LSCs, with only one case positive for Acanthamoeba spp. The Candida spp. fungal elements (20.0%) and Staphylococcus coagulase negative bacteria (60.5%) were the predominant microorganisms. Biodiversity markers namely: Simpson (0.802) and Shannon-Weiner (1.895) diversity indices were high in comparison to other studies. Monthly lens renewal (OR = 1.333, p = 0.040) and soft lens wear (OR = 4.66, p = 0.066) enhanced the installation of fungal elements.

Conclusions: The behaviors of contact lens wearers observed in this work corroborate those of all studies of contact lens wearers. The complexity of the recommended procedure and poor understanding of the instructions may explain any imperfections. This study highlights a high level of biodiversity in LSCs, and the strains in circulation are almost potentially pathogenic for humans.