Anterior chamber metal fragments after phacoemulsification surgery.

PURPOSE: To determine whether metal fragments can be shaken loose from phaco needles during surgery and embed in the iris. SETTING: Private practice, Vernon, British Columbia, Canada, and scanning electron microscope laboratory, Mastel Precision, Rapid City, South Dakota, USA. METHODS: The surfaces and rims of new and used phaco needles and the lumens of halved new needles were examined by scanning electron microscopy (SEM). To determine whether the fragments on the phaco needles were approximately the same size as those seen in the iris, a photograph of an eye with metal fragments imbedded in the iris was projected and the image size of the metal fragments approximated by using their magnification value. The magnification scale of the SEM images was used to determine the size of the metal fragments photographed on the phaco needles. RESULTS: The SEM studies of new phaco needles revealed tiny fragments of metal firmly adherent to the interior, exterior, and rim surfaces. No fragments were detected on the surfaces of the used phaco needles. Two metal fragments in the eye photograph were calculated to be 0.20 x 0.20 mm and 0.15 x 0.20 mm. Those in the SEM photos were calculated to be 0.03 to 0.10 mm. CONCLUSION: Althogh SEM of new titanium phaco needles revealed adherent metal fragments on their lathed surfaces, no fragments were found on used phaco needles. The iris fragments calculated from a projected photograph were slightly larger than those from the SEM micrographs, supporting the conclusion that annealed metal fragments shook loose from the phaco needles. This indicates that ultrasonic activation of a new phaco needle with metal fragments annealed to its surface causes fragments to release and embed in the iris.

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.