Toxic Anterior Segment Syndrome (TASS)

What happens in TASS

During cataract surgery, instruments and solutions are introduced into the front chamber of the eye. If something toxic enters the eye, it damages the delicate tissues, especially the corneal endothelium, the single layer of cells that keeps the cornea clear by pumping out fluid. The result is inflammation and corneal swelling (edema), which clouds vision.

Causes

TASS has been linked to:

• residue on reused surgical instruments, including detergents, enzymatic cleaners and ultrasound bath contaminants
• bacterial endotoxins (from contaminated water in sterilizers, not live infection)
• solutions with the wrong pH, concentration or preservatives
• some medicines injected into the eye at the wrong dose
• ophthalmic viscoelastic material residue
• metal or polishing residue on intraocular lenses

Because it relates to surgical processes, TASS often appears in clusters at the same facility, prompting investigation of cleaning and sterilization procedures.

Symptoms and signs

• blurred vision, often noticed on the first day after surgery
• a hazy cornea from limbus to limbus (edge to edge)
• redness
• mild to moderate pain (often less than expected for the degree of inflammation)
• inflammatory cells in the front chamber, resembling uveitis; sometimes a layer of white cells (hypopyon)
• a dilated or irregular pupil that reacts poorly
• raised eye pressure in some cases

TASS vs infectious endophthalmitis

Because endophthalmitis can destroy vision rapidly, doctors treat as infection if there is any doubt, and may sample fluid from the eye for culture and give intraocular antibiotics.

Diagnosis

• slit-lamp examination of the cornea, anterior chamber and iris
• eye pressure measurement
• examination or ultrasound of the back of the eye to check the vitreous
• corneal thickness measurement (pachymetry) and endothelial cell counts during follow-up

Treatment

• intensive topical corticosteroid drops (such as prednisolone acetate, hourly at first), sometimes with oral steroids
• close follow-up, often daily at first
• pressure-lowering drops if eye pressure rises
• treatment of persistent corneal swelling: hypertonic saline drops, and in permanent damage, a corneal transplant (endothelial keratoplasty)
• glaucoma surgery if the drainage system is permanently damaged
• reporting to the facility and regulators to identify and fix the cause

Outlook

Mild and moderate TASS usually resolves over days to weeks with steroid treatment, and vision recovers. Severe cases can permanently damage the corneal endothelium or the eye's drainage system, causing chronic corneal clouding or glaucoma that may need further surgery.

Frequently asked questions

What is toxic anterior segment syndrome?

TASS is a sterile inflammatory reaction in the front of the eye caused by a toxic substance entering the eye during surgery, usually cataract surgery. It typically appears within 12 to 48 hours and causes blurred vision and a hazy cornea.

How is TASS different from endophthalmitis?

TASS is non-infectious, starts earlier (within 1 to 2 days), causes less pain and improves with steroids. Endophthalmitis is an infection that usually starts later, causes severe pain and needs urgent antibiotics. Doctors treat as infection if unsure.

Is TASS curable?

Most mild to moderate cases resolve with intensive steroid eye drops over days to weeks. Severe cases may leave permanent corneal swelling or high eye pressure that needs further treatment, such as a corneal transplant.

Is blurry vision normal after cataract surgery?

Mild blur for a day or two is common and should improve steadily. Vision that gets worse, increasing pain, redness or light sensitivity are not normal and need prompt review by your eye surgeon.