Development of a cold storage medium with lyophilized antimycotic

Introduction: Cornea cold storage media available on market do not contain antimycotics. A new cold storage medium was designed with lyophilized antimycotic in order to prevent yeast contaminations of donor corneas intended for transplantation after cold storage.

Purpose: The aim of this study was to assess the antimycotic activity of the new cold storage medium by time kill studies and to perform an evaluation of donor corneas preserved in a new cold storage medium at 4°C for 14 days.

Material and methods: Antimycotic activity was determined by time-kill studies in vitro using and initial inoculum concentration of 10⁵ cfu/ml of C.Albicans (ATCC10231 and clinical isolate). The killing rate of the microorganisms was monitored after 1, 3 and 7 days of incubation with the new medium at 4°C.

10 donor corneas, 5 couples not suitable for transplantation, were procured and evaluated according to standard procedures of Monza Eye Bank, Italy. Tissues were evaluated pre-processing and after 7 and 14 days of cold storage for endothelial cell density (ECD) using Keratoanalyzer and endothelial morphology and mortality were determined according Stocker method. Central corneal thickness (CCT) was measured using OCT Visante (Zeiss), epithelial integrity, corneal transparency were evaluated using Slit lamp.

Results: Time kill studies in vitro showed that all the microorganism were completely eliminated after 7 days of incubation at 4°C and at least 3log₁₀ microbial decrease was obtained already after 24h of storage at 4°C.

New medium-treated and control tissues showed similar ECD, mortality and endothelial morphology after 14 days of cold storage. CCT ranged from 580 to 690 micron for whole period the cold storage for both groups. Slit lamp analysis showed comparable corneal transparency and epithelial integrity in treated and control group.

Conclusions: New cold storage medium showed excellent antimycotic properties at 4°C in time kill studies and exhibited an excellent biocompatibility with donor corneas.