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Final report: No single identifiable source of TASS outbreak
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Originally appeared in the Nov. 1 2006 issue of Ocular Surgery News.
In its final report, the special task force investigating the recent outbreak of toxic anterior segment syndrome could not identify a single cause, product or source associated with the sharp increase in TASS cases.
The American Society of Cataract and Refractive Surgery's TASS task force is headed by Nick Mamalis, MD. The investigators based their final report on completed protocol forms and questionnaires from 66 centers.
The data did not suggest a single source of the outbreak, but investigators did find several potential etiologic factors related to instrument reprocessing and use of surgical products. The task force noted particular concern over reusable cannulated instruments. Investigators found that many centers had only a brief interval between cases to reprocess and clean instruments, and several centers also reported occluded I/A tips. Such occlusion could have prevented proper flushing and allowed a build up of cortex, viscoelastics and other materials, possibly leading to TASS, the report said.
Because of this, the task force recommended using disposable cannulas whenever possible. When any device must be flushed and reused, flushing should only be carried out with sterile deionized/distilled water. Additionally, residual materials from water baths, enzymes or detergents may cause TASS. The task force recommended any instruments sterilized with these methods be subsequently rinsed with sterile deionized/distilled water, according to the report.
Ultrasound water baths present a greater contamination risk due to gram-negative bacteria and subsequent endotoxins, which are highly heat-stable and survive autoclaving. The report recommends ultrasound baths be cleaned after each use, or at least at the end of each day. The filters, water chambers and interiors of autoclave units should also be regularly cleaned to prevent endotoxin contamination.
The task force further recommended developing written protocols for cleaning cataract surgery equipment to reduce errors in reprocessing and to ensure both competency and compliance. Several centers acknowledged the absence of such protocols, the report noted.
Additionally, the task force strongly recommended exclusively using preservative-free additives in ocular medications. In particular, epinephrine must be free of potentially toxic stabilizing agents, such as bisulphites or metasulphites. Intracameral anesthetics also pose a potential contamination risk because such agents may not be fully evacuated by short ultrasound times, the report said.
No specific risks were associated with intracameral antibiotics when used in the proper dosages, nor with any single IOL or lens injector when such devices were properly cleaned, the report noted.
The TASS task force will continue to evaluate data and is working to establish further guidelines for cleaning, sterilization and processing ophthalmic instruments to prevent future outbreaks, according the report.