Toxic Anterior Segment Syndrome (TASS) Clinical Presentation

Updated: Oct 05, 2021
  • Author: Jean Deschênes, MD, FRCSC; Chief Editor: John D Sheppard, Jr, MD, MMSc  more...
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In the setting of postoperative inflammation, distinguishing toxic anterior segment syndrome (TASS) from infectious endophthalmitis is very important. However, this can be difficult, because both conditions can present in a similar fashion. [1, 2]

The hallmark of TASS is its rapid onset, usually within 12 to 24 hours. Rarely, TASS can present as delayed onset postoperative inflammation, which can confuse it with infectious endophthalmitis. [3] Patients with TASS are usually pain free; however, if pain is present, it is mild.



Depending on the severity of the insult, the presentation can vary. Features that are unique to TASS include the following:

  • Limbus-to-limbus corneal edema is considered to be the classic finding of TASS; however, not all cases have this finding. Most frequently, the occurrence appears as a milder form with increased anterior chamber cells in excess of that seen after surgery. [1]

    Diffuse limbus-to-limbus corneal edema and anterio Diffuse limbus-to-limbus corneal edema and anterior segment inflammation noted in a patient with toxic anterior segment syndrome (TASS).
  • Anterior chamber reaction can be moderate to severe with the presence of hypopyon and fibrin. Unlike infectious endophthalmitis, vitreous inflammation is rare, and, if it occurs, it is considered to be the result of a posterior diffusion from the anterior chamber. [3]

  • An unreactive dilated pupil may be noted.

  • The intraocular pressure can be elevated secondary to trabecular meshwork damage.

  • Cystoid macular edema has been reported in a few cases.

Unlike infectious endophthalmitis, TASS often rapidly improves after topical steroids are instituted, which serves as a distinguishing feature from infectious endophthalmitis.

The following table summarizes the classic presentation of TASS and infectious endophthalmitis to help differentiate the two entities. [1, 2]

Table 1. Differentiating Toxic Anterior Segment Syndrome and Infectious Endophthalmitis (Open Table in a new window)

Signs and Symptoms


Infectious Endophthalmitis


12-24 hours usually

2-7 days usually


Usually none but can be mild to moderate

Usually severe

Corneal edema

Limbus to limbus

Specific to area of trauma

Intraocular pressure

May increase suddenly

Usually not elevated

Anterior chamber inflammation

Moderate-to-severe anterior chamber reaction with increased white blood cells and fibrin. Hypopyon may be noted.

Moderate-to-severe anterior chamber reaction. Fibrin is variable. Hypopyon often present (75% of the time).


Very rare

Always present


Fixed and dilated


Lid swelling

Usually not evident

Often present

Visual acuity



Response to steroids

Dramatic improvement




Multiple causes and associations have been implicated with TASS. They can be divided into the following categories:

Extraocular substances that inadvertently enter the anterior chamber during or after surgery include the following [1, 2] :

  • Topical antiseptic agents

  • Talc from surgical gloves

  • Ophthalmic ointment

Products that are introduced into the anterior chamber as part of the procedure include the following [1, 2] :

  • Anesthetic agents (eg, lidocaine 2% vs 1%)

  • Preservatives (eg, benzalkonium chloride)

  • Inappropriately reconstituted intraocular preparations

  • Mitomycin-C

  • Intraocular lenses, including phakic intraocular lenses

  • Contaminated irrigating solutions (eg, balanced salt solution contaminated with bacterial endotoxin)

One study shows that corneal toxicity from intracameral agents may be associated with the concentration of free radicals present in the agents. [4]

Contaminants on the surfaces of intraocular surgical instruments that have accumulated as a consequence of inadequate or inappropriate instrument cleaning include the following [1, 2] :

  • Denatured viscosurgical devices

  • Enzymatic detergents

  • Bacterial endotoxin contamination of ultrasound water bath cleaners

  • Impurities of autoclave steam

  • Oxidized metal deposits and residues

Because of the multiple causes and associations implicated, it is often difficult for the surgical center to isolate a cause directly.