Optimized Autologous Serum Eye Drops: Microbial Contamination After Extended Length of Use of Two Different Types of Eye Dropper Bottles

Purpose: This study analyzed the contamination rate of autologous serum (AS) eye drops in 2 different eye dropper bottles (glass bottles with a filter-free rubber tip vs. plastic bottles with a one-way-valve) and evaluated patient preference regarding bottle type. Methods: In this prospective, comparative, nonrandomized study, 17 patients with severe dry eye disease administered AS eye drops using the standard glass eye dropper bottle and the plastic eye dropper bottle. Patients recorded the date/time of start and end of use. The tip of the eye dropper bottle was cultivated on a chocolate agar plate and the residual content of the bottle in a thioglycolate medium. Patients also filled in a questionnaire regarding bottle preference. The main outcome was microbial contamination of the eye dropper bottle. Results: In total, 229 glass and 104 plastic eye dropper bottles were analyzed for microbial contamination. The average duration of use was 3.8 days for glass and 4.1 days for plastic bottles. Tip contamination rates increased proportionally with duration of use and were comparable for both bottle types. Content contamination for glass bottles reached 50% after 2.5 days. For plastic bottles, the content of only 1/104 was contaminated. None of the patients developed clinical symptoms or complications related to bacterial contamination. Overall, 80% of patients preferred the glass bottle. Conclusions: Plastic bottles with a filter system preventing backflow of eye drops from the bottle tip, successfully prevented the microbial contamination of AS content inside the bottle over an extended period. Bottle tips were contaminated similarly in both types of bottles.