Contamination Rates and Economic Evaluation of Reusing Medicated, Preservative-Free, Single-Use Eye Drops

Introduction: Preservative-free eye drops are commonly packaged in single-dose vials, so it is recommended to discard the vial upon first use, even if some solution remains. This study aims to examine the risk of infection associated with repeated use of these eye drops and evaluate the economic impact of such practice. Methods: 80 vials were divided into three test groups and one control group (C). Volunteers were trained to use three different installation techniques to simulate the real-life use of these eye drops. The vials were then recapped and kept in the refrigerator for 24 hours. Next, the remaining solution in each vial was cultured, as well as group C vials, and contamination and infection rates were compared between each group against the control group. The infection probabilities were applied to a decision tree model to compare the cost of reusing the vials. Results: Group A results were (4/20) (20%) p ≥ 0.10, while group B got only 1 out of 20 (5%) p ≥ 1.0, finally group D (5/20) (25%) p ≤ 0.04 and this was the only group that showed a significantly higher rate of infection (pathogenic rate) as an indicator to the importance of the instillation technique. The cost and savings ratio ranged from EGP 20.1 to EGP 20.4 for the base case according to the different installation techniques. Conclusion: Reusing single-use vials within 24 hours is associated with cost savings independent of the installation technique. Further real-world studies are warranted as actual experienced patients are expected to provide pragmatic conclusions.