Microbial Assessment of Reclosable Single-Day Use Ophtioles Containing Autologous Serum Eye Drops

Background: Autologous serum eye drops (ASEDs) are produced without preservatives and need to be stored at 2-8 °C while in use. This study aims to analyze the behavior of specific bacteria and fungi in the case of contamination during the usage of single-day use ophtioles containing ASED. Methods: This is a prospective experimental study conducted at the Department of Ophthalmology, University Hospital of Zurich (USZ), and a regulatory-licensed, independent, external laboratory. The laboratory performed microbial testing on the ASEDs with 11 microorganisms in 100% concentration or 50% diluted using the original 2.5 mL ASED ophtioles provided by the Eye Bank of the Department of Ophthalmology, USZ. Storage took place at 2-8 °C and 20-25 °C. The acceptance criterion was the absence of microbial growth between opening (T0), 24 h afterwards (T24), and 48 h afterwards (T48). Results: The acceptance criteria were met for all microorganisms for 2-8 °C. For seven microorganisms, the acceptance criteria were met for 2-8 °C and 20-25 °C. For four microorganisms, the acceptance criteria were only met for 2-8 °C. Conclusions: No relevant growth was observed in any of the test strains from T0 to T24 and T48 at 2-8 °C, demonstrating the microbiological safety of reclosable single-day use ophtioles containing unpreserved ASEDs when stored at 2-8 °C.