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

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.

Eighty vials were divided into three test groups and one control group (C). Group A comprised sterile installation; in group B the vial tip touched the volunteers' eyelid while in group D the volunteers' fingertip touched the vial tip. The vials were then recapped and kept in the refrigerator for 24 h. 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. The infection probabilities were applied to a decision tree model to compare the cost of reusing the vials.

Group A pathogenic contamination was detected in four out of 20 individual vials tested (20%), p = 0.11, while group B had only a single contamination (5%), p > 0.99; finally, group D demonstrated five contamination incidents (25%), p < 0.04. This was the only group that showed a significantly higher rate of infection (pathogenic rate) as an indicator of the importance of the instillation technique. The cost and savings ratio ranged from Egyptian Pounds (EGP) 20.1 to EGP 20.4 for the base case (i.e., assuming that both opportunistic and pathogenic bacteria were infectious, while commensal bacteria were not) according to the different instillation techniques.

Within this hypothetical economic model, reusing single-use vials within 24 h demonstrated potential cost savings independent of the instillation technique. Further real-world studies are warranted as actual experienced patients are expected to provide pragmatic conclusions.