Particulate contamination in disposable corneal trephines

In two cases scheduled for corneal transplantation, edges of donor corneal buttons were discolored by a black contaminant transferred from the disposable trephines. Trephines from two different manufacturers produced this same problem. Scanning electron microscopy and energy-dispersive x-ray analysis indicated that the contaminant was a mixture of stainless steel particles from the trephine and silicon carbide abrasive used in sharpening.