A System of Operative Surgery, Volume 4 (of 4)

by Unknown

The operation of iridectomy differs widely in its performance, according to the different conditions for which it is used. Hence it is better to prefix the condition for which it is employed, thus: preliminary iridectomy, optical iridectomy, glaucoma iridectomy.

Apart from being one of the stages of removal of a cataract, already described, it is performed as an independent operation in the following conditions:—

1. For optical purposes (optical iridectomy).

2. For the relief of glaucoma, primary and secondary (glaucoma iridectomy).

3. For small growths at the free margin of the iris.

4. For prolapse of the iris through a wound.

OPTICAL IRIDECTOMY

Indications. Iridectomy for optical purposes is performed for a centrally situated nebula of the cornea and in some very rare cases of small central opacities in the lens. In the latter condition it is rarely of much value, as nearly all the rays which enter the eye pass through the central portion of the lens. Further, in this condition the lens may be removed and better sight obtained with glasses. Optical iridectomy should always be performed opposite a clear portion of the cornea, the lower segment of the eye being chosen, otherwise the coloboma may be subsequently covered by the upper lid. The site of election for the operation is downwards and inwards, but in all cases the patient should be carefully examined in the following ways: (1) the vision is tested, any refraction being corrected without a mydriatic; (2) the pupil is then dilated, and the best situation for the iridectomy determined by means of a stenopaic slit. The vision must be definitely improved by the use of these before operation can be advised. The disadvantage of an iridectomy is that it allows more light to enter the eye, and, if the periphery of the lens be uncovered, spherical aberration may result. For both these reasons, therefore, it is advisable to make the iridectomy as small as possible. Tattooing of the central scar in the cornea will often diminish the amount of light entering the eye, but before undertaking the latter operation, the eye should be cocainized and the area covered with a piece of black paper to see if the vision is improved thereby.

Instruments. Speculum, fixation forceps, bent broad needle or small keratome, Tyrrell’s hook, iris forceps, scissors, and spatula.