Enhanced accuracy is necessary for refractive surgery instrumentation.

New optical zone markers, diamond knives, and gauge blocks were ordered from a random selection of manufacturers and inspected by an independent metallurgical engineer. This study revealed workmanship flaws and poor instrument accuracy. None of the 26 optical zone markers examined came with instructions as to whether the incisions were to be carried to or from the inside diameter or the outside diameter of the corneal impression made by the marker. Two markers had a 100 microns or greater error in their centering devices and one had a centering device off center by 210 microns. Two of the seven diamond micrometer knives had broken blade tips and uneven footplates; two knives had misaligned blades and uneven footplates, one knife had extremely roughly finished footplates, and one knife had a 100 microns error in its micrometer. All the knives had a wobble in the blade shaft upon advancement and had rounded footplates, making blade extension verification difficult. Five of seven blade gauges were accurate to within 10 microns; two had errors of more than 60 microns which could lead to incisions too deep or too shallow and micro- or macroperforations of the cornea during refractive surgery. It is recommended that all refractive surgery instruments be carefully inspected under a high power micron-level microscope at the time of purchase and routinely thereafter.