Comparison of Contamination Rates of Designs of Rigid Contact Lens Cases

Purpose. To compare the rates of bacterial contamination in cylindrical and flat contact lens cases of orthokeratology (ortho-k) users and to investigate their preference of lens case design based on ease of use and handling. Methods. Twenty-four children receiving ortho-k treatment were recruited. Each subject was given one cylindrical and one flat lens case, of which one side (50% right, 50% left) was sealed to prevent usage. Subjects were instructed to either rinse the case with water and air dry or rinse with multipurpose solution (MPS) and refill with MPS for storage after lens removal. After 1 month, cases were collected for culture, which was performed on the screw top, inner surface of cases, and also the holder for cylindrical cases. Each subject/parent completed a questionnaire about preference of case design. Results. No significant differences in rates of surfaces contaminated were found between cleaning methods. Overall, 30% of both inner surfaces and screw tops of the cases yielded potentially pathogenic organisms, with significantly higher numbers present on both the inner surfaces (p = 0.003) and the screw tops of the flat cases (p = 0.001). Contamination of the inner surfaces with only normal flora occurred exclusively in the flat cases, but the screw tops of both case types frequently yielded only normal flora. Cylindrical case holder contamination was similar to the inner surface. There was a strong preference (75%) for the cylindrical cases, with subjects/parents citing ease of use and cleaning, good appearance and transparency, and reduced amount of MPS used. Conclusions. Although correct lens case care remains the most important factor in reducing contamination of the case, use of the cylindrical case design, preferred by the majority of subjects/parents, significantly reduced contamination in ortho-k subjects. The method used for cleaning the lens case had no effect on the rates of contamination in this study. (Optom Vis Sci 2012;89:E1030-E1034)