Study on the relationship between bacterial endotoxin and the onset of toxic anterior segment syndrome

PURPOSE: To comprehensively analyze the contamination status of pyrogen including bacterial endotoxins, considered as one of the onset agents of toxic anterior segment syndrome (TASS), in medical devices used for cataract surgery, and to improve the cleanliness of the devices by new sterilization technology. SETTING: Innovative Decontamination Technology Development and Evaluation Center, Miura Co. Ltd., Yokohama, Japan. DESIGN: Experimental study. METHODS: The pyrogen levels of the medical devices were evaluated using a direct human cell-based pyrogen test that is not affected by the recovery ratio, unlike the endotoxin test. Pyrogen inactivation tests were further performed using low-temperature ozone/hydrogen peroxide mixed gas sterilization. RESULTS: Significant pyrogen levels from 0.22 to 11.6 endotoxin units (EU)/product as a worst case were detected in 7 of 11 medical devices. These products might have exceeded the previously reported threshold (0.02 to 0.05 EU/eye) for inducing dose-dependent inflammatory responses in the mammalian vitreous during actual use. However, our study revealed that pyrogen contamination in the devices was reduced below the detection limit after ozone/hydrogen peroxide mixed gas sterilization under an elaborate treatment mode at 50°C. CONCLUSIONS: The precise amount of pyrogen required to induce human TASS remains unknown; however, currently available medical products for intraocular surgery were found to be contaminated with nonnegligible amounts of pyrogens, and the possibility of a causal relationship between actual product use and the onset of TASS cannot be ruled out. This potential risk could be eliminated by replacing the current sterilization method with ozone/hydrogen peroxide mixed gas treatment.