Toxic Anterior Segment Syndrome (TASS)
Clinical Presentation
TASS is an acute, sterile, postoperative inflammatory reaction of the anterior segment that typically presents within 12-48 hours after uncomplicated intraocular surgery, characterized by prominent limbus-to-limbus corneal edema and severe anterior chamber inflammation without vitreous involvement. 1, 2
Key Clinical Features
- Timing: Symptoms develop acutely within the first 12-72 hours after anterior segment surgery, most commonly following cataract extraction 2, 3, 4
- Visual symptoms: Decreased visual acuity and ocular discomfort are the primary complaints 1, 2
- Corneal findings: Prominent limbus-to-limbus diffuse corneal edema due to endothelial cell damage is the hallmark sign 1, 2, 3
- Anterior chamber inflammation: Severe inflammation with cells, aqueous flare, fibrinous exudates, keratic precipitates, and often hypopyon formation 1, 2, 3
- Distinguishing feature: No vitreous involvement, which helps differentiate TASS from infectious endophthalmitis 1
- Microbiologic findings: No bacteria isolated from ocular samples, confirming the sterile nature 3
Late-Onset Presentation
- TASS can rarely present as late-onset disease (weeks after surgery), manifesting with fibrin formation, keratic precipitates, and white material on intraocular lens surfaces 5
Management Algorithm
Immediate Recognition and Treatment
Initiate intensive topical corticosteroid therapy immediately upon clinical diagnosis, as prompt treatment is critical to prevent permanent complications. 1, 2
First-Line Treatment Protocol
- Topical corticosteroids: Intensive hourly dosing (e.g., prednisolone acetate 1% every hour while awake) as the primary treatment 2, 3
- Topical NSAIDs: Add nonsteroidal anti-inflammatory drops as adjunctive therapy to control inflammation 4
- Cycloplegics: Use cycloplegic agents to reduce ciliary spasm and prevent posterior synechiae formation 2
Treatment Duration and Tapering
- Continue intensive steroid therapy for 4-5 weeks with gradual tapering based on clinical response 5
- For late-onset cases, combination of topical and oral steroid treatment may be necessary for 4-5 weeks 5
Critical Differential Diagnosis
TASS must be distinguished from infectious endophthalmitis, as the treatments differ fundamentally—TASS requires steroids while endophthalmitis requires antibiotics. 2, 3
Key Distinguishing Features
- TASS: Onset within 12-48 hours, limbus-to-limbus corneal edema, no vitreous involvement, negative cultures 1, 2, 3
- Endophthalmitis: Often presents later (2-7 days), vitreous involvement with vitritis, positive cultures, progressive worsening despite steroids 2
- Initial approach: Because clinical features are initially indistinguishable, obtain aqueous and vitreous cultures before initiating treatment 3
Prevention Strategies
Prevention is paramount and requires meticulous attention to all surgical equipment, solutions, and medications, as TASS has multiple potential etiologies. 1, 2, 4
Major Known Causes to Eliminate
- Preservatives in ophthalmic solutions: Use only preservative-free solutions for intraocular use 3
- Denatured ophthalmic viscosurgical devices (OVDs): Ensure proper storage and handling of viscoelastics 3
- Bacterial endotoxin: Implement rigorous sterilization protocols to eliminate endotoxin contamination 3
- Intraocular lens-related factors: Verify proper IOL preparation and handling 3
- Contaminated surgical equipment: Any device or substance used during surgery may be implicated 3, 4
Systematic Prevention Protocol
- Equipment sterilization: Careful attention to cleaning and sterilization of all surgical instruments, as inadequate sterilization is a common cause 4
- Solution verification: Verify all intraocular solutions, medications, and irrigating fluids for contamination or improper preparation 4
- Traceability system: Implement a comprehensive traceability system for all surgical instruments and intraocular fluids used during surgery 1
- Updated guidelines: Follow continuously updated prevention guidelines as new causes of TASS are identified 1
- Immediate investigation: When a cluster occurs, systematically change materials and equipment in series to identify the causative agent 4
Sight-Threatening Complications
Permanent Sequelae Requiring Vigilance
- Permanent corneal decompensation: Irreversible corneal edema from endothelial cell death may require corneal transplantation 1, 3
- Intractable glaucoma: Chronic elevation of intraocular pressure from permanent trabecular meshwork damage 1, 3
- Cystoid macular edema: Can develop as a secondary complication affecting final visual outcomes 1
Monitoring and Follow-Up
- Close monitoring during the acute phase and long-term follow-up to detect chronic complications 1
- Most patients achieve good clinical and visual outcomes with prompt diagnosis and adequate treatment 2
Common Pitfalls to Avoid
- Delayed recognition: Failure to recognize TASS within the critical 12-48 hour window delays steroid initiation and worsens outcomes 1, 2
- Treating as endophthalmitis: Prolonged antibiotic therapy without steroids when TASS is the actual diagnosis 3
- Inadequate steroid intensity: Using insufficient steroid dosing or duration allows progression to permanent complications 2, 5
- Missing late-onset cases: Failing to suspect TASS when inflammation occurs weeks after surgery 5
- Incomplete prevention audit: Not systematically investigating all potential sources when TASS occurs 4