• Eighteen patients developed a toxic endothelial cell destruction syndrome following normal intraocular surgery, caused by a detergent residue originating from irrigating cannulas. The residue occurred after the concentration of a detergent solution had been increased from 0.4% to 4%, in combination with insufficient cleaning of the cannulas. Mass spectrometric analysis revealed the detergent to contain a nonionic ethoxylated fatty alcohol (6% vol/vol). Quantitative endothelial vital staining and in vitro corneal endothelial perfusion demonstrated endothelial toxic effects at the 1% and 0.06% level for the detergent and the pure ethoxylated fatty alcohol, respectively. Permeability studies showed that the toxic effects occurred as a result of endothelial barrier breakdown.