Comparison of three permanent intraocular magnets.

A comparison was performed of three small-gauge, permanent, rare-earth, intraocular magnets to assist the posterior segment surgeon with the decision as to which magnet to purchase or to use in different clinical situations. The magnetic force was measured at varying distances from the instrument tip using a 1/8-inch steel ball as the test object. There were small differences in magnetic strength between the three instruments that may have clinical significance in certain situations. Two of the instruments had a retractable magnet within an outer sleeve, allowing for controlled attraction and release of a magnetic foreign body by the surgeon.