Description, etiology, and prevention of an outbreak of diffuse lamellar keratitis after LASIK

PURPOSE: To describe an outbreak of diffuse lamellar keratitis (DLK) and provide a hypothesis about the etiology. METHODS: A retrospective analysis was carried out on 328 eyes of 220 patients who underwent LASIK over 9 months. The occurrence of DLK using two different methods of cleaning and sterilizing surgical instruments and an autoclave reservoir were analyzed. Microbial analyses were carried out by two laboratories on samples obtained from the original autoclave reservoir and tubing. A chi-square test was used to compare qualitative values. The Student t test was used to compare numerical values. RESULTS: Forty-six (24.5%) of 188 cases of DLK were diagnosed. Sphingomona paucimobilis and Burkholderia pickettii were isolated in the reservoir of the steam sterilizer. Electron microscopy revealed gram-negative microbes on the tubing walls. After changing the reservoir of the steam sterilizer and implementing a new cleaning and sterilization protocol based on air-drying the instruments and draining and drying the reservoir of the sterilizer, the occurrence of DLK stopped. No statistically significant correlation was noted between the occurrence of DLK and gender, age, or volume of tissue removed. CONCLUSIONS: Data obtained during this DLK outbreak support the theory that a bacterial endotoxin, which can survive short-cycle steam sterilization, could be responsible for an outbreak of DLK. We recommend cleaning and sterilization protocols based on air-drying surgical instruments and leaving the reservoirs completely dry at the end of each surgical day.