Toxic anterior segment syndrome update

It's deja-vu all over again. Yogi Berra Toxic anterior segment syndrome (TASS) is an acute sterile anterior segment inflammation that develops after anterior segment surgery. Findings associated with TASS typically present within 12 to 48 hours of surgery. The most common clinical symptom is significant blurred vision and the most common clinical finding, diffuse “limbus-to-limbus” corneal edema secondary to widespread damage to the corneal endothelium. A second hallmark of TASS is breakdown of the blood–aqueous barrier, leading to increased aqueous flare and inflammatory cells in the anterior chamber, which often leads to a hypopyon with associated fibrin. Finally, TASS can cause significant damage to the iris, which leads to pupillary irregularity, iris transillumination defects, and secondary glaucoma due to damage to the trabecular meshwork. A review of TASS with an accompanying editorial was published in early 2006.1,2 A major outbreak of TASS began in the late winter and early spring of that year throughout much of North America. Extensive analysis of the outbreak did not find a single factor involved in the TASS cases but did find multiple potential factors, the most common involving the cleaning and sterilization of ophthalmic instruments. This outbreak led to the formation of the TASS Task Force, chaired by myself and Henry Edelhauser, PhD. The task force comprised multiple physicians, nurses, technicians, and representatives from industry involved in the analysis of TASS. Members of the Food and Drug Administration as well as the United States Center for Disease Control were also involved. The task force's work culminated in a special report on recommended practices for cleaning and sterilizing intraocular surgical instruments to prevent the occurrence of TASS.3 Two questionnaires were developed to help in the analysis of TASS outbreaks; one addresses the cleaning and sterilization of ophthalmic instruments, and the second assesses the use of products and medications during anterior segment ophthalmic surgery. These questionnaires are available to the ophthalmic community through the American Society of Cataract and Refractive Surgery (ASCRS) web site to facilitate reporting of TASS cases and help identify potential causes of TASS. An update of the most common causes of TASS over the past 3 years is published in this issue (pages 1073–1080). Questionnaires submitted to the ASCRS web site by surgical centers reporting cases of TASS were analyzed at the John A. Moran Eye Center at the University of Utah by my colleagues and me. Data from site visits performed by task force members were also included in this most recent analysis of TASS cases. Data from 76 centers completing questionnaires were combined with data from 54 site visits for analysis. Over this 3-year period, 909 cases of TASS were reported out of more than 50 000 cataract surgeries performed concurrently at the reporting centers. The 54 site visits reported an additional 367 cases of TASS out of more than 140 000 procedures performed concurrently. The most common findings associated with TASS were related to problems with instrument cleaning and sterilization. Inadequate flushing of the phaco and irrigation/aspiration (I/A) handpieces after surgery was the most commonly observed behavior leading to TASS. Many centers were not using the recommended 120 cc per port to flush the handpieces. An additional finding was that almost 40% of the respondents stated they had experienced occluded I/A tips, which is consistent with inadequate flushing. Other common practices associated with TASS involved the use of enzymatic cleaners on ophthalmic instruments. The problems that can be associated with enzymatic cleaners include incorrect concentration of cleaners and, more significant, inadequate rinsing of enzymes or detergents from the ophthalmic instruments before their use. Any residue of an ophthalmic enzyme or detergent may be toxic to the anterior segment of the eye during surgery. Other common practices associated with TASS were the use of reusable cannulas as well as the reuse of single-use devices. An additional association was the use of ultrasonic baths for cleaning instruments. Almost 80% of the reporting centers did not adequately rinse and clean the ultrasound bath after each use as recommended. Poor instrument maintenance was also found to occur commonly in the onsite visits of centers experiencing cases of TASS. In terms of the association between TASS and fluids and medications used during surgery, the use of preserved epinephrine in the balanced salt solution (BSS) occurred in 52% of the reporting centers. Almost one-third of the centers reported using topical anesthetic agents with preservatives. Medications given intracamerally or added to the BSS irrigant were another potential source for TASS. The updated report highlights that cleaning and sterilizing ophthalmic instruments remains a critical factor in TASS cases. Inadequate flushing of phaco and I/A handpieces following a procedure was widespread. This can lead to residual material within the handpiece, such as cortex or an ophthalmic viscosurgical device, that can be toxic to the anterior segment of the eye. Reusable small-bore instruments such as cannulas are also a potential source of TASS because the small internal diameters and opening make it difficult to adequately clean these instruments. It is extremely important to thoroughly flush reusable cannulas and handpieces at the end of each case to prevent materials from building up within the instruments. The use of enzymatic cleaners and detergents is also problematic. Residue of these cleaning materials, which are inadequately flushed from ophthalmic instruments, can be toxic to the corneal endothelium as well as to the cells of the trabecular meshwork and the iris. Inadequate cleaning of ultrasound water baths used for cleaning instruments is another issue. While ultrasound baths are useful in removing bulk contamination from instruments, thorough flushing of ophthalmic handpieces and cannulated instruments at the conclusion of each case should eliminate the possible buildup of residual material within these instruments. There is very little bioburden left in ophthalmic instruments, which may obviate ultrasound cleaning. The findings from analysis of the product and medication questionnaire highlighted that it is critically important that only preservative-free medications are injected intracamerally during anterior segment surgery. This is especially important in terms of the epinephrine added to the BSS solution during surgery. Preservatives in the epinephrine can be toxic, but stabilizing agents such as bisulphites or metabisulphites can also be toxic; it is important that the epinephrine be bisulphite free as well as preservative free. Any anesthetic agent or other medication injected into the eye should be preservative free and used at the proper concentration to avoid toxic reactions. Although TASS is very rare and often occurs sporadically, it can result in significant inflammation leading to ocular morbidity. Surgeons and surgical center staff should be aware of TASS, and appropriate protocols for cleaning, processing, and sterilizing ophthalmic instruments should be in place. It is also important that the medications and solutions used in the eye during cataract surgery are preservative free and the proper dose. The ophthalmic community must maintain ongoing vigilance to prevent outbreaks of TASS.