An investigation of enzymatic detergents as a potential cause of toxic anterior segment syndrome.

Objective: To investigate whether enzymatic detergents used in cleaning ophthalmic surgical instruments can cause toxic anterior segment syndrome (TASS)-like responses in a rabbit model.

Design: Randomized, investigator-masked, controlled experimental animal study.

Participants: Thirty-five New Zealand white rabbits.

Methods: The rabbit eyes were randomized into 7 treatment groups to receive intracameral injection of 1 of 3 different doses of Medline Dual Detergent or Enzol Detergent, or sterile limulus amoebocyte lysate reagent water as a control. The eyes were evaluated for anterior segment inflammation at baseline and at 1, 3, 6, 24, 48, and 72 hours after treatment by slit-lamp biomicroscopy.

Main Outcome Measures: Anterior chamber (AC) inflammation, including cells, flare, fibrin, and iris injection; time course of inflammation; and residual detergent levels in luminated instruments.

Results: Moderate to marked injection of the iris vessels was seen as early as 1 hour after treatment with the enzymatic detergents in 41 of 60 eyes, with the response being more severe in the Enzol Detergent-exposed eyes. Severe iris hemorrhages were accompanied by blood in the AC in 13 eyes, which usually persisted through 72 hours, with an associated increase in AC cell and flare. Corneal haze was present in 52 of 56 eyes 1 hour after treatment, but was mild and resolved within 24 hours in all but the Enzol 4.5%-exposed eyes. Median AC cell and flare peaked at 6 hours and resolved by 48 hours.

Conclusions: Enzymatic detergents caused a severe but unusual response from the iris when injected intracamerally into rabbit eyes. This response has not been reported in humans with TASS. The time course of inflammation was faster (peak at 6 hours) and resolved more quickly (within 48 hours) than TASS. Simulated cleaning and extraction studies indicate that the level of residual detergent to which a patient could be exposed is significantly less than the lowest dose used in this study. Because that low dose caused no significant observations other than injection of the iris vessels, these results do not support residual enzymatic detergents on surgical instruments as a cause for TASS.