Bacterial load and protein deposits on 15-day versus 1-day disposable hydrophilic contact lenses

This study quantified the bacterial load and protein deposits on 1- and 15-day disposable contact lenses after use in normal wearers.

Sixteen patients were randomly assigned to a 1-day contact lens (1-Day Acuvue) in one eye and to a 15-day contact lens (Acuvue) in the contralateral eye. Only one specified solution was allowed for the care of 15-day lenses. All patients were evaluated every month for 6 months (at times T1, T2, T3, T4, T5, T6). At times T1, T3, and T5, the lenses were removed in a sterile fashion and sent for laboratory quantification of Staphylococcus aureus and Pseudomonas aeruginosa. At T2, T4, and T6, quantification of protein deposits was determined, and at T0 and T6, impression cytology of the conjunctiva was performed.

P. aeruginosa was not identified on any lens. At T1, T3, and T5, S. aureus was significantly greater on the 1-day versus 15-day lenses (p < 0.001). In contrast, protein deposits were significantly greater on the 15-day lenses at all time points (T2, T6: p < 0.01; T4: p < 0.05). Impression cytology of the 15-day lens eyes revealed a worsening trend compared to the 1-day lens; however, no statistically significant differences were found between the two groups (p = 0.29).

Results of this study suggest that the use of cleaning and preservative solutions can alter the ocular surface bacterial environment of the contact lens wearer and that these changes are not a direct consequence of contact lens wear. The bactericidal activity of these solutions could, with time, also affect ocular surface cells, leading to contact lens intolerance and ocular surface disease.