Importance: The proportion of postkeratoplasty fungal infections is rising steadily. However, the most commonly used corneal storage medium in the United States, Optisol-GS, does not contain an antifungal additive.
Objectives: To determine the lowest concentration of amphotericin B supplementation in Optisol-GS that will eliminate fungal contaminants effectively without resulting in toxic effects to the cornea and to determine what role light exposure plays in the efficacy and safety of amphotericin B supplementation.
Design, setting, and materials: An in vitro laboratory efficacy study measured fungal colony growth in 10 vials of Optisol-GS supplemented with different concentrations of amphotericin B after inoculation with Candida albicans in light-exposed and light-protected conditions. Two vials each were supplemented with amphotericin B at concentrations of 0.06, 0.12, or 0.225 μg/mL; the remaining 2 vials received no C albicans inoculation and no antifungal supplementation (negative controls). After 24 hours, 1 vial from each pair was exposed to light for the remainder of the study. On days 2, 7, and 14, 1 mL of solution was removed from each vial and incubated at 36°C for 48 hours. In a separate safety study, 12 pairs of corneas were divided between amphotericin B supplementation and the control condition; 4 corneas each received the different amphotericin B concentrations. An additional 4 pairs of corneas were stored in the 0.225-μg/mL concentration, and 1 cornea from each pair was exposed to light for the duration of the study. Data were collected November 16, 2014, and analyzed from November 16 to 18, 2014, for the efficacy study; they were collected from April 14 to May 27, 2015, and analyzed from May 28 to 30, 2015, and on December 23, 2015, for the safety study.
Main outcomes and measures: Fungal colony growth was measured from the Optisol-GS vials. Corneal endothelial cell density, endothelial cell viability, and epithelial toxic effects were measured in stored corneas.
Results: In the efficacy study, Optisol-GS supplemented with concentrations of 0.06 and 0.12 μg/mL of amphotericin B eliminated all fungal contaminants by day 7 and reduced fungal growth on day 2 by a mean of 3.5 colony-forming units (95% CI, -6.19 to 13.20 colony-forming units; P = .34), a 77.8% decline compared with the postoperative controls. Optisol-GS supplemented with the 0.255-μg/mL concentration of amphotericin B eliminated all fungal contaminants by day 2. In the safety study, no evidence was found of toxic effects to the cornea in corneas stored in Optisol-GS supplemented with amphotericin B at any concentration compared with paired controls. No difference in the efficacy or safety of the light-exposed compared with light-protected amphotericin B-supplemented Optisol-GS was identified.
Conclusions and relevance: In this study, Optisol-GS supplemented with a 0.255-μg/mL concentration of amphotericin B effectively eliminated fungal contaminants within 48 hours and did not result in added toxic effects to the cornea. These results do not prove that amphotericin B should be added to Optisol-GS; larger-scale studies and cost-benefit analyses need to be completed. Given the increasing incidence of postkeratoplasty fungal infection, however, the addition of amphotericin B to Optisol-GS deserves further investigation.