Magnets for the removal of magnetizable foreign bodies from the eye are of two types—(1) a small magnet, which is inserted into the globe, (2) a giant magnet, which is used to attract the foreign body in the eye from the outside.
Fig. 125. Small Electro-magnet for extracting Pieces of Steel from the Eye. It is made to work direct off the electric main.
Surgeons differ as to which is the best method to employ. The statistical results of both are about the same. Many surgeons in this country, and with them the author, prefer the small magnet, especially of the recent more powerful type (Hirschberg), which runs off the main electric current, for the following reasons: it is more accurate (after localization by the X-rays), there is less trauma to the globe involved, it is more portable, and, when the foreign body is in the anterior or the posterior chamber, it is much easier to extract it with a small magnet than with a large one.
With the small magnet. Instruments. Beer’s knife, fixation forceps, magnet (Fig. 125), and suture. The points of the magnet, which are detachable, are sterilized by boiling.
Operation. The foreign body is first localized accurately by means of the X-rays. If it lies near the wound of entrance the magnet point is inserted, the electric circuit completed, and the foreign body withdrawn, the wound of entrance being enlarged if necessary. If the foreign body lies at some distance from the wound, as for instance in the vitreous, an antero-posterior incision is made in the sclerotic, as near to it as possible, by plunging the knife through the conjunctiva and the sclerotic, the former having previously been drawn to one side so as to form a valvular opening. The size of the incision should be such that it will admit the point of the magnet and allow the foreign body to come out, the size of the foreign body being judged by the X-ray photograph. After the knife has been withdrawn, the point of the electro-magnet is inserted and the circuit closed, the magnet being withdrawn with the foreign body attached to it. The conjunctival wound is closed by a suture if necessary. If the foreign body be situated in the anterior or posterior chamber or the lens, an incision should be made into the anterior chamber with a keratome, the point of the magnet inserted, and the foreign body withdrawn. In cases in which the foreign body is deeply embedded in the lens, more especially in patients over thirty years of age, extraction of the lens together with the foreign body should be performed.
Complications. Immediate. Failure to extract the foreign body may arise from—
1. The foreign body being embedded in lymph. It is therefore of the utmost importance that the operation should be performed as soon as possible after the injury.
2. The foreign body being deeply embedded in the sclerotic so that the magnet will not exert sufficient traction to withdraw it.
3. The foreign body being non-magnetic (all steel is not magnetic).