Microbial decontamination of human donor eyes with povidone-iodine: penetration, toxicity, and effectiveness

Background/aims-Povidone-iodine (PVP -I) is applied for microbial decontami nation of human eyes donated for transplantation. Concentrations and immers ion times vary greatly. The effectiveness and toxicity of PVP-I were assess ed for different decontamination protocols. Methods-Human donor eyes and corneas were immersed in different concentrati ons (5-100 mg/ml) of PVP-I for different times (2-30 minutes). The penetrat ion of iodine into the corneal tissue was assessed by x ray microanalysis, Microbial contamination was determined by taking cultures of the limbal are as and storage solutions and by incubation of the corneoscleral buttons in antibiotic-free culture medium. Cytotoxicity of PVP-I for corneal fibroblas ts in culture was assessed using the MTT assay. Results-Depending on concentration and immersion time iodine was found to p enetrate into the epithelium, Bowman's layer, and stroma in amounts equival ent to 2-40 mg/ml PVP-I. The MTT assay demonstrated that 2.5 mg/ml PVP-I ca used total damage to fibroblasts in vitro. Rinsing eyes with tap water and subsequent immersion in PVP-I reduced the rate of contamination from 82 out of 106 to 69 out of 106 and 37 out of 106, respectively. Antibiotics in th e storage medium further reduced contamination from about 40% to 3%. Microb ial contamination was not reduced by increasing the concentration and immer sion times beyond 5 mg/ml PVP-I for 2 minutes. Conclusion-Immersion of human donor eyes in 5 mg/ml PVP-l solution for 2 mi nutes significantly reduces microbial contamination of donor corneas withou t relevant penetration of iodine into the corneal layers. Higher PYP-I conc entrations and longer immersion times do not further reduce contamination, whereas the amount of iodine penetrating time corneal layers is elevated ab ove the level cytotoxic for corneal fibroblasts. In view of this, concentra tions above 5 mg/ml of PVP-I and immersion periods over 2 minutes are not r ecommended for reduction of the contamination rate of donor eyes.