Toxic Anterior Segment Syndrome (TASS) 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. Disease TASS is a rare acute anterior segment reaction that can occur after surgery. Etiology 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) • Preservative • Metallic precipitate General Pathology Severe inflammatory reactions in response to the contamination, toxins, imbalanced solutions, medications or preservative 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. Pathophysiology TASS is an activation of inflammatory cascades in the anterior chamber in response to external material or wrong solutions during cataract surgery. The response is visible 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 any kind of preservatives in intraocular solutions, intracameral medications or irrigating solutions • Use of fresh ophthalmic visosurgical devices • Adequate sterlization of instruments and tubing according to the manufacturers 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 Diagnosis Symptoms: • Decreased or blurry vision shortly after surgery • Pain Signs: • Acute severe inflammatory reaction of anterior chamber within 12-48 hours after surgery • Corneal edema limbus to limbus • Dilated or irregular pupil • Increased intraocular pressure • Lack of bacterial or fungal growth from cultures of intraocular taps • Good response to topical ophthalmic steroid drops History Acute onset of anterior chamber inflammation 12-48 hours after uneventful anterior segment surgery Physical examination Full examination is very important. Evaluation of visual acuity, pupil size and reaction, slit-lamp exam, eye pressure and dilated fundus exam. Signs • Severe anterior chamber inflammation within 12-48 hours post-operative period • Corneal edema extending from limbus to limbus • Dilated or irregular pupil • Increased intraocular pressure • Hypopyon Symptoms • Vision loss or blurry vision within 12-48 hours after surgery • Pain ranging from mild to severe • Photophobia Clinical diagnosis Clinical diagnosis is made on many factors. The physician should note the time of onset after eye surgery in conjunction with the patients 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 Management 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. The patient needs to be evalauted 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 Topical steroid treatment. Medical therapy Most TASS patients respond well to topical corticosteroids (1% Prednisolone acetate) given hourly. Patients with mild 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 which is a longer response than in mild cases. In the severe case, there may be permanent damage, persistent corneal edema, chronic persistent inflammation, fixed dilated pupil, refractory glaucoma secondary to trabecular meshwork damage and cystoid macular edema. In severe cases there may be a need for systemic steroid treatments. 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, inflammation, corneal recovery should be observed carefully. Surgery TASS is a post surgical event after an anterior segment surgery. At the time of surgery there is no indication of the problem. After surgery if TASS develops then there is a need for intraocular aqueous and vitreous tap for culture. In a severe case of TASS with persistent corneal edema then there is a need for corneal transplant. In a severe case of TASS with refractory glaucoma, patient may need to undergo glaucoma/intraocular pressure lowering surgery. Surgical follow up • Frequent follow-ups are needed to monitor eye pressure, vision, detail Slit-Lamp examination to track inflammation, cornea endothelial function, and iris. • Close observation for bacterial infection • Infectious etiology needs to be ruled out • Gonioscopy examination • Dilated fundus exam • Corneal recovery needs to be followed closely. In a severe case of TASS the patient may need corneal transplant • In refractory glaucoma, the eye pressure should be closely monitored. In a severe case, if the pressure is non responsive to medication and there is no sign of recovery then there is a need for glaucoma surgery Complications • 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 Prognosis Most of the cases of TASS are successfully treated with topical steroids, non-steroidal anti-inflammatory drops, or both. The intense inflammatory reaction can cause serious damage to intraocular tissues including the corneal endothelium which results in cornea edema, iris atrophy (either dilated or irregular pupil), trabecular meshwork damage with possible secondary glaucoma. The tissue damage can result in vision loss.
Posted on: Sat, 01 Nov 2014 15:10:02 +0000
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