CHAPTER III
OPERATIONS UPON THE IRIS
IRIDOTOMY
Indications. Iridotomy is an operation which is performed when the iris has become drawn up after a cataract extraction, so that there is no pupil, or the pupillary area is covered by the upper lid. A long interval should elapse between the extraction and the iridotomy, since these cases have usually suffered from cyclitis following the operation. Iridotomy should not be performed for at least six months after all signs of cyclitis have disappeared, for the frequent failure of the operation is due to the fact that the opening made in the iris and underlying capsule becomes filled with fibrous exudation as the result of cyclitis, which is frequently set up again by the operation if undertaken before a sufficient time has elapsed for the eye to settle down after the inflammation. The ideal operation, therefore, is to make an artificial pupil with the least amount of trauma to the ciliary body.
Instruments. Speculum; fixation forceps; a long, narrow, bent ‘broad needle’; Tyrrell’s hook, iris scissors, iris forceps, and spatula.
Operation. Many operations have been devised for this most troublesome condition, but the following is the one that the author has found to be successful.
The operation is usually performed under a general anæsthetic, but this is not essential.
| Fig. 102. Iridotomy. Showing the incision with a long, bent broad needle. | Fig. 103. Iridotomy. Showing the method of withdrawing the band of iris and capsule with a Tyrrell’s hook. |
First step. The surgeon stands facing the patient on the same side as the eye to be operated on. The long, bent, broad cutting needle is passed into the anterior chamber from the limbus downwards and inwards, and is driven directly through the iris and underlying capsule. The needle is then made to pass in an upward and outward direction behind the iris into the pupillary area above, or if no pupil be present, again through the iris (Fig. 102). The bent broad needle is made to cut laterally by slightly deflecting the handle so as to produce a band of iris and capsule; the cutting needle is then withdrawn.
Second step. A Tyrrell’s hook, bent to the correct angle, is passed beneath the band (Fig. 103), which is drawn into the wound and removed with iris scissors. A large opening is thus obtained with a minimum amount of trauma. If the hook should slip, the band may be seized with iris forceps, withdrawn from the wound, and removed.