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Microbial decontamination of human donor eyes with povidone-iodine: penetration, toxicity, and effectiveness
1Netherlands Ophthalmic Research Institute, Amsterdam, Netherlands.
Background/Aims:
Povidone-iodine (PVP -I) is applied for microbial decontamination of human eyes donated for transplantation. Concentrations and immersion times vary greatly. The effectiveness and toxicity of PVP-I were assessed for different decontamination protocols.
Methods:
Human donor eyes and corneas were immersed in different concentrations (5-100 mg/ml) of PVP-I for different times (2-30 minutes). The penetration of iodine into the corneal tissue was assessed by x ray microanalysis. Microbial contamination was determined by taking cultures of the limbal areas and storage solutions and by incubation of the corneoscleral buttons in antibiotic-free culture medium. Cytotoxicity of PVP-I for corneal fibroblasts in culture was assessed using the MTT assay.
Results:
Depending on concentration and immersion time iodine was found to penetrate into the epithelium, Bowman's layer, and stroma in amounts equivalent to 2-40 mg/ml PVP-I. The MTT assay demonstrated that 2.5 mg/ml PVP-I caused 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 the storage medium further reduced contamination from about 40% to 3%. Microbial contamination was not reduced by increasing the concentration and immersion times beyond 5 mg/ml PVP-I for 2 minutes.
Conclusion:
Immersion of human donor eyes in 5 mg/ml PVP-I solution for 2 minutes significantly reduces microbial contamination of donor corneas without relevant penetration of iodine into the corneal layers. Higher PVP-I concentrations and longer immersion times do not further reduce contamination, whereas the amount of iodine penetrating the corneal layers is elevated above the level cytotoxic for corneal fibroblasts. In view of this, concentrations above 5 mg/ml of PVP-I and immersion periods over 2 minutes are not recommended for reduction of the contamination rate of donor eyes.
Insights
A 5 mg/ml povidone-iodine (PVP-I) solution for 2 minutes effectively decontaminates donor eyes for transplantation. Higher concentrations or longer times increase toxic iodine penetration without improving microbial reduction.
Area of Science:
- Ophthalmology
- Microbiology
- Materials Science
Background:
- Povidone-iodine (PVP-I) is used for microbial decontamination of human donor eyes for transplantation.
- Current protocols for PVP-I concentration and immersion time vary significantly.
- Assessing the effectiveness and toxicity of different PVP-I decontamination protocols is crucial.
Purpose of the Study:
- To evaluate the effectiveness of various povidone-iodine (PVP-I) concentrations and immersion times for microbial decontamination of human donor eyes.
- To determine the extent of iodine penetration into corneal tissues under different treatment conditions.
- To assess the cytotoxicity of PVP-I on corneal fibroblasts.
Main Methods:
- Human donor eyes and corneas were exposed to varying concentrations (5-100 mg/ml) and durations (2-30 minutes) of PVP-I.
- Iodine penetration was quantified using X-ray microanalysis.
- Microbial contamination was assessed via cultures from limbal areas, storage solutions, and corneoscleral buttons.
- Corneal fibroblast cytotoxicity was evaluated using the MTT assay.
Main Results:
- Iodine penetration into corneal layers (epithelium, Bowman's layer, stroma) correlated with PVP-I concentration and immersion time.
- A PVP-I concentration of 2.5 mg/ml proved cytotoxic to corneal fibroblasts in vitro.
- Reducing contamination rates was observed with rinsing and PVP-I immersion, with antibiotics further decreasing it to 3%.
- Increasing PVP-I concentration or immersion time beyond 5 mg/ml for 2 minutes did not enhance microbial reduction.
Conclusions:
- A 2-minute immersion in 5 mg/ml PVP-I solution effectively reduces microbial contamination in donor corneas.
- This optimal protocol minimizes iodine penetration into corneal layers to non-toxic levels.
- Higher PVP-I concentrations or longer immersion times increase toxic iodine penetration without additional decontamination benefits.
- Protocols exceeding 5 mg/ml PVP-I or 2 minutes are not recommended for donor eye decontamination.
