July 15, 2006
5 min read

More than 100 centers affected by second TASS outbreak

A task force conducting investigations named at least a dozen potential causes, including possibly inadequate cleaning practices.

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FAIRFAX, Va. – More than 100 centers have reported cases of toxic anterior segment syndrome from February through May 2006, according to a task force of the American Society of Cataract and Refractive Surgery.

This outbreak of toxic anterior segment syndrome (TASS) seems to be separate from and unrelated to an earlier outbreak of TASS that was associated with balanced salt solution manufactured by Cytosol Ophthalmics, according to Nick Mamalis, MD, who has been leading an investigation into the reports.

Nick Mamalis

No single cause or point source related to the most recent outbreak of TASS has been identified, an ASCRS news release said, but “several potential etiologic factors … have arisen from review of the data.”

In a statement released by ASCRS, Dr. Mamalis said that in the period from March to May, the number of TASS cases reported to the Intermountain Ocular Research Center has been “five times the normal rate.”

“There are a half a dozen potential causes,” he said. “It’s baffling, that’s what’s driving us crazy, and no one factor is consistently popping up.”

Dr. Mamalis is heading up an ASCRS ad hoc task force investigating the outbreak that includes Henry Edelhauser, PhD, of Emory University; Walter Hellinger, MD, an epidemiologist at the Mayo Clinic in Jacksonville, Fla.; Arjun Srinivasan, MD, at the Centers for Disease Control; and Samuel Masket, MD, the president of ASCRS.

Dr. Mamalis, who continues to field all reports of TASS incidents, spoke to Ocular Surgery News after the release of the preliminary report.

After more than 2 months of investigations and weekly conference calls with industry and other centers to collect data, Dr. Mamalis said, the good news is that the number of cases began dropping off in April and has remained low since then.

Product-related factors

The preliminary report issued by ASCRS on June 22 listed a number of potential factors, which have been identified through questionnaires filled out by centers that reported cases of TASS. In the report, these factors were divided into those related to products and those related to instrument reprocessing between cases.

Potential factors related to products include addition of epinephrine to balanced salt solution. The epinephrine “must be truly preservative free,” the preliminary report said. Epinephrine solutions containing stabilizing agents such as bisulphites are not considered preservative free, according to the report. Bisulphite is potentially toxic to the corneal endothelium and other structures of the anterior segment, the report said.

Preoperative use of nonsteroidal anti-inflammatory drugs and intraoperative use of intracameral antibiotics, if improperly dosed, mixed or injected into the eye, were listed as possible factors.

Intracameral anesthetics are also a potential factor, “especially given the short ultrasound time in the majority of cases,” the ASCRS report said.

Dr. Mamalis explained that with modern, efficient surgical techniques less time is spent in the eye with the phaco tip, and less irrigation fluid is pumped through the eye. He credited Dr. Edelhauser with the theory that phaco has become so efficient that it does not allow enough time to flush the anesthetic from the eye.

“A lot of times we are in the eye with our ultrasound for less than 5 minutes,” Dr. Mamalis said. “If you have intracameral lidocaine in there with a viscoelastic, 5 minutes may not be enough time to completely wash out the lidocaine, and a higher-than- expected dose can be left in the anterior chamber, which can cause inflammation.”

Another finding of the preliminary report was that most IOLs used in the TASS cases reported were Alcon lenses.

“However,” the report noted, “given the large market share of Alcon, it is unclear whether or not this represents a larger than expected relationship of one particular IOL manufacturer to the TASS cases.”

Dr. Mamalis said, “I certainly want to get across that we are not implicating a particular IOL in this outbreak.”

Instrument reprocessing

Dr. Mamalis told Ocular Surgery News that instrument cleaning practices seem to be a factor in some of the reported cases of TASS.

“We are finding more and more that the issue may be involved in the cleaning, processing and what’s being done to the instruments between cases,” Dr. Mamalis said.

The ASCRS report listed a number of findings related to instrument reprocessing.

Reusable cannulas may allow a residue of ophthalmic viscosurgical devices, cortex or other materials that can be toxic when injected into the anterior chamber, the report said.

Short surgical turnaround time may affect the ability to clean instruments properly between cases, according to the report. Reusable phaco and irrigation and aspiration hand pieces could be potential sources of TASS.

Instrument cleaning with ultrasound baths, enzymes and detergents could be related to TASS if the cleaning materials are not thoroughly flushed from the instruments, the ASCRS statement said.

Complete cleaning should include flushing instruments with 120 cc of sterile, deionized water, Dr. Mamalis explained. However, he said, that is a time consuming process and may not be properly done in surgical centers with rapid turnover of cases.

Extra care must be taken with the specialized, small-bore cannulas used for hydrodissection, he added.

“Those really need to be thoroughly flushed because if not, a cannula or the tip of an instrument that’s got a bore in it may have residual viscoelastic or residual cortex left inside that isn’t pushed out completely. During the next case that can be flushed into the eye and cause inflammation,” he said.

He recommends the use whenever possible of disposable cannulas for injecting viscoelastic or balanced salt solution, as well as disposable phaco machine tubing, to eliminate any chance of residue.

Separate outbreaks

The outbreak of TASS that is discussed in this preliminary report is separate from an outbreak that began last year, associated with balanced salt solution made by Cytosol Ophthalmics and distributed by several companies. That outbreak eventually resulted in the recall of Cytosol’s balanced salt solution products.

Dr. Mamalis said that, despite the short span of time between the two TASS outbreaks, they seem to be two separate events.

“I do not think that they are related,” he told Ocular Surgery News.

Members of the task force initially speculated that the increase in TASS reports that began in March was related to raised awareness of TASS brought about by the Cytosol-related outbreak, Dr. Mamalis said. But the large number of reports in the recent outbreak, from “well over 100 centers,” indicates that it stems from more than increased awareness, he said.

There have also been reports from centers in Israel and South America, he said, so “I don’t think this is strictly a U.S. or North American phenomenon.”

Industry cooperation

Alcon has been among the major ophthalmic companies cooperating with the task force in the investigation of the current TASS outbreak. In addition to participating in the task force’s weekly conference calls, the company has given an unrestricted educational grant to ASCRS and the American Society of Ophthalmic Registered Nurses to aid in the investigation, according to Kathleen Golden, senior communications specialist at Alcon.

“As a leader, we felt obliged to take a supportive role with the task force,” she told Ocular Surgery News. “Our number 1 concern is just trying to find what the potential causes are, and anything we can do to support the TASS task force we are making sure we are doing.”

Dr. Mamalis said, “Alcon has been extremely helpful in not only being involved in the weekly phone calls and in the discussions, but even putting together a video symposium.”

The ASCRS preliminary report said that of 53 of the 114 centers that reported cases of TASS directly to a single manufacturer, 41 of the centers have not had any further cases as of the first week of June. Twelve of the centers have had more cases since their initial reports in April, the report said.

The TASS task force will continue to analyze cases and will formulate recommendations for prevention of the problem, the preliminary report said.

For more information:

  • Nick Mamalis, MD, can be reached at John Moran Eye Center, University of Utah, 50 N. Medical Drive, Salt Lake City, UT 84132; 801-581-6586; fax: 801-581-3357; e-mail: nick.mamalis@hsc.utah.edu.
  • Kathleen Golden, senior communications specialist at Alcon, can be reached at Alcon Inc., 6201 South Freeway, Fort Worth, TX 76134-2099; 817-551-4963; fax: 817-302-4300; e-mail: kathleen.golden@alconlabs.com.
  • Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.
  • Michelle Dalton is Managing Editor of OSNSuperSite.com. She writes daily updates on developments in all aspects of ophthalmology.