Toxic Anterior Segment Syndrome

From EyeWiki

Toxic Anterior Syndrome (TASS) is a rare and devastating complication of intraocular surgery.  TASS is an acute sterile anterior chamber inflammatory reaction that usually develops 12-48 hours after anterior segment surgery.  Late-onset TASS has also been reported. The condition is responsive to topical steroids in most cases.

Disease Entity

Toxic anterior segment syndrome (TASS) is an acute severe intraocular inflammation accompanied by diffuse corneal edema within 1-2 days of anterior segment surgery which is most commonly associated with cataract surgery. TASS is a form of sterile, noninfectious endophthalmitis with or without pain, marked decrease in vision, diffuse corneal edema that extends limbus to limbus, photophobia and severe anterior chamber reaction, occasionally with hypopyon. TASS presents within 12-24 hours after surgery where infectious endophthalmitis typically develops 2-7 days after surgery. TASS is responsive to topical steroids in most cases. 


The etiology of TASS may be multi-factorial with numerous potential causes.

  • Bacterial endotoxins or particulate contamination of balanced salt solutions
  • Intraocular irrigating solutions with abnormal PH, osmolarity or ionic composition
  • Denatured Ophthalmic Viscosurgical Devices (OVD)
  • Intraocular medications (antibiotics in the irrigation solutions or intracameral antibiotics)
  • Topical ointments
  • Inadequate sterilization of surgical instruments and tubing
  • Inadequate flushing of instruments between cases resulting in build-up of ophthalmic viscosurgical devices (OVD)
  • Preservatives
  • Metallic precipitates


General Pathology

Severe inflammatory reactions in response to the contamination, toxins, imbalanced solutions, medications or preservatives in the medications.  This is a sterile anterior segment reaction.  There is no bacterial or fungal infection, although one potential cause of the inflammatory reaction is secondary to bacterial endotoxins.


TASS is an activation of  inflammatory cascades in the anterior chamber in response to external material or inappropriate solutions during cataract surgery.  The response is typically apparent and symptomatic 12-48 hours after surgery.

Primary prevention

  • Use of proper balance salt solution (BSS) with the correct pH, osmolarity, and ionic composition
  • Good filtration of the BBS at the manufacturing site to eliminate particulate contamination and endotoxins
  • Avoid preservatives in intraocular solutions, intracameral medications or irrigating solutions
  • Use of fresh ophthalmic visosurgical devices
  • Adequate sterlization of instruments and tubing according to the manufacturer's protocol
  • Standard and clear operative and instrument processing procedures (SOP) need to be implemented
  • The staff and surgeon should be well aware of the SOPs




Acute onset of anterior chamber inflammation 12-48 hours after uneventful anterior segment surgery 

Eye examination

Full examination is very important.  Evaluation of visual acuity, pupil size and reaction, slit-lamp exam, eye pressure and dilated fundus exam.


  • Vision loss or blurry vision within 12-48 hours after surgery
  • Pain ranging from mild to severe
  • Photophobia


  • Acute severe inflammatory reaction of anterior chamber within 12-48 hours after surgery
  • Corneal edema extending from limbus to limbus
  • Dilated or irregular pupil
  • Increased intraocular pressure
  • Hypopyon
  • Lack of bacterial or fungal growth from cultures of intraocular taps 
  • Good response to topical ophthalmic steroid drops

Clinical diagnosis

Clinical diagnosis is made based on many factors. The physician should note the time of onset after eye surgery in conjunction with the patient's symptoms. The anterior chamber should be examinied carefully for anterior chamber reaction, intraocular pressure and severity of vision loss. Patients tend to respond very well to topical steroid treatment.

Diagnostic procedures

All patients should have a slit lamp exam and dilated fundus exam. The posterior pole may be difficult to view if there is severe anterior chamber reaction. In these situations, the patient should have an ultrasound B-scan to rule out any posterior reaction.  Both aqueous and vitreous taps are sent for culture to investigate for an infectious process.

Laboratory test

  • Bacterial culture for both aerobic and non aerobic 
  • Fungal culture 

Differential diagnosis

  • Infectious endophthalmitis
  • Retained lens material
  • Uveitis


Most patients do well with medical management using topical steroids.  In rare cases, depending on the severity there may be a need for systemic steroid treatment.  The patient should be followed closely and evaluated by a retina specialist to rule out infectious causes.

On rare severe cases, there is a need for further surgical intervention.  The patient may need cornea transplant, glaucoma surgery or both.

General treatment

Medical therapy

Most TASS patients respond well to topical corticosteroids (1% Prednisolone acetate) given hourly.  Mild or early cases will respond to steroids rapidly as evidenced by clearing of the inflammation and decrease in intraocular pressure.  In cases of moderate TASS, the clearing may take up to 3-6 weeks.  In severe cases, which may need systemic steroids, there may be permanent damage, including persistent corneal edema, chronic persistent inflammation, fixed dilated pupil, refractory glaucoma secondary to trabecular meshwork damage and cystoid macular edema.  In severe cases

Medical follow up

The patient should be followed very closely, especially for the several hours and days after the onset of treatment.  The patient needs be evalauted for recovery and response rate.  The eye pressure, level of inflammation, corneal recovery should be observed carefully. Gonioscopy examination is necessary to rule out retained lens fragments.


TASS is a post surgical event after an anterior segment surgery. 

If TASS develops, then there is usually a need for intraocular aqueous and vitreous tap for culture. In severe cases of TASS with persistent corneal edema, patients may need corneal transplantation. In refractory glaucoma, the eye pressure should be closely monitored.  If the pressure is not responsive to medical management, glaucoma surgery may be necessary.

Of note, in a major outbreak of 147 eyes published by Oshika et al, 29.3% cases required surgery, including irrigation of the anterior chamber, vitrectomy, and IOL removal.


  • Severe inflammation
  • Pain
  • Vision loss
  • Iris atrophy either dilated or irregular pupil
  • Cornea endothelial damage with corneal edema
  • Trabecular meshwork damage with possible secondary glaucoma


Most cases of TASS are successfully treated with topical steroids, non-steroidal anti-inflammatory drops, or both.
If not resolved after 6 weeks, permanent damage is more likely to occur. The intense inflammatory reaction can cause serious damage to intraocular tissues including the corneal endothelium, which results in cornea edema, iris (either dilated or irregular pupil, and atrophy), and trabecular meshwork damage with possible secondary glaucoma. Tissue damage can result in vision loss.

Additional Resources


  1. Manson MC, Mamalis N, Olson RJ.  Toxic anterior segment inflammation following cataract surgery.  J Cataract Surg 1992;  18: 184-189
  2. Mamalis N, Edelhauser HF, Dawson DG, Chew J, LeBoyer RM, Werner L.  Toxic anterioe segment syndrome.  J Cataract Refract Surg  2006; 32: 324-333
  3. Carolee M. Cutler Peck, Jacob Brubaker, Sue Clouser, Chris Danford, Henry E. Edelhauser, Nick Mamalis   Toxic anterior segment syndrome: Common causes   Journal of Cataract & Refractive Surgery  July 2010;  Vol. 36(Issue 7): 1073-1080
  4. Oshika T, Eguchi S, Goto H, Ohashi Y. Outbreak of Subacute-Onset Toxic Anterior Segment Syndrome Associated with Single-Piece Acrylic Intraocular Lenses. Ophthalmology. 2017;124(4):519e23
  5. Hernandez-Bogantes E, Navas A, Naranjo A, Amescua G, Graue-Hernandez EO, Flynn HW Jr, Ahmed I. Toxic anterior segment syndrome: A review. Surv Ophthalmol. 2019;64(4):463-476
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