Toxic Anterior Segment Syndrome
Toxic anterior segment syndrome (TASS) is an acute sterile postoperative inflammation. The symptoms and signs of TASS may mimic those of infectious endophthalmitis and include photophobia, severe reduction in visual acuity, corneal edema, and marked anterior chamber reaction, occasionally with hypopyon (Fig 11-17). However, TASS presents within 12 to 48 hours of surgery, whereas acute infectious endophthalmitis typically develops 3–10 days postoperatively. Other potentially distinguishing features of TASS include diffuse, limbus-to-limbus corneal edema; anterior chamber fibrinous exudate; a dilated, irregular, or nonreactive pupil; and elevated IOP. The pathologic changes are limited to the anterior chamber. Pain is typically much milder than that experienced with an infection. When endophthalmitis is suspected, diagnostic and therapeutic interventions (described later in this chapter) are indicated.
Figure 11-17 Toxic anterior segment syndrome.
© 2019, American Academy of Ophthalmology.)
TASS is thought to be caused by the inadvertent introduction of a substance toxic to the corneal endothelium or uvea. A 2018 report by a TASS task force showed the risk factors to be inadequate flushing and rinsing of handpieces, use of enzymatic detergents, and use of ultrasonic baths. Ultrasonic baths are susceptible to contamination with gram-negative bacteria and may result in residue on instruments of heat-stable bacterial endotoxin. It is necessary to properly clean and maintain ultrasound baths, if they are used.
Other causes of TASS include surgical glove residue or talc on instruments or IOLs; use of a denatured OVD; substitution of sterile water for balanced salt solution; intraocular use of inappropriate irrigating solutions, antibiotics, or anesthetics; and inadvertent introduction of substances into the anterior chamber. Subconjunctival antibiotic injections and topical ophthalmic ointments applied with patching have been reported to enter the anterior chamber through corneoscleral incisions. Skin cleansers containing chlorhexidine gluconate have caused irreversible corneal edema and opacification when they come into contact with the endothelium. Clusters of TASS due to irrigation fluids tainted with bacterial endotoxin have also been reported. Ideally, all solutions used intracamerally are free of stabilizers and preservatives and buffered to physiologic osmolarity and pH.
Treatment of TASS consists of intensive topical corticosteroids until the inflammation subsides. A brief course of systemic corticosteroids may be beneficial. Frequent follow-up is necessary to monitor IOP and to reassess for signs of bacterial infection.
Bodnar Z, Clouser S, Mamalis N. Toxic anterior segment syndrome: update on the most common causes. J Cataract Refract Surg. 2012;38(11):1902–1910.
Chang DF, Mamalis N; Ophthalmic Instrument Cleaning and Sterilization Task Force. Guidelines for the cleaning and sterilization of intraocular surgical instruments. J Cataract Refract Surg. 2018;44(6):765–773.
Mamalis N. Toxic anterior segment syndrome (TASS). Focal Points: Clinical Modules for Ophthalmologists. American Academy of Ophthalmology; 2009, module 10.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.