Magnetized forceps for intraocular foreign body removal: which one is suitable?

Magnetic intraocular foreign bodies can be removed with magnetized disposable forceps. Aim of this study is to compare the forceps magnetizability of different size, form and manufacturer.

The forceps were magnetized using an established procedure. The inducible magnetic flux density was measured at the tip of the forceps. The mass that can be lifted with the magnetized forceps was then tested using steel balls in BSS solution. The weight of the metal parts of the forceps was measured.

The magnetic flux density that could be induced, the weight of the steel balls that could be lifted and the mass of stainless steel used in the forceps were as follows: Alcon end-grasping 23G: 7.12 mT, 87.43 mg, 1191 mg; Alcon end-grasping 25G: 6.43 mT, 87.43 mg, 1189 mg; Alcon serrated: 4.39 mT, 63.78 mg, 1284 mg; Alcon serrated 23G: 3.62 mT, 13.74 mg, 1200 mg; Alcon serrated 25G: 2.4 mT, 13.74 mg, 1195 mg; DORC end-grasping 23G: 5.52 mT, 32.54 mg, 153 mg; Synergetics end-grasping 23G: 4.35 mT, 16.37 mg, 193 mg; Vitreq BV end-grasping 23G: 2.65 mT, none, 88 mg.

The magnetizability of a disposable microforceps seems to depend on the mass of steel at the tip of the forceps. The structure of the iron lattice could have an even greater influence. Not every disposable forceps can be sufficiently magnetized for this technique.