The immediate results of this operation are satisfactory provided that enough sclerotic be removed to produce a filtration cicatrix. As yet sufficient time has not elapsed for any statistical results to be obtained, but the cases in which the operation has been performed are reported as satisfactory.
POSTERIOR SCLEROTOMY
Indications. Posterior scleral puncture is performed—
(i) For the relief of tension, the indications for which have already been described under the indications for iridectomy in glaucoma (see [p. 218]).
(ii) For the evacuation of fluid behind a detached retina.
The operation in the latter instance, although not yielding very satisfactory results with regard to the reattachment of the retina, may be carried out with some hope of success in certain cases. Before performing the operation the pathological cause of the detachment should be carefully investigated, for it is obvious that it would be useless to perform the operation in a case of detachment due to a choroidal tumour or if definite bands of fibrous tissue could be seen in the vitreous pulling off the retina. Undoubtedly it should be undertaken as soon as possible after the detachment has occurred and the puncture should enter the space filled with subretinal fluid. Whether the puncture should penetrate the overlying retina is still a disputed point.
After the operation a pressure bandage should be applied and the patient should be kept on his back and not allowed to raise his head from the pillow for at least three weeks. This latter part of the treatment is most essential; indeed as good results may be obtained with complete rest as by performing scleral puncture. Unfortunately, recurrence is very liable to take place whichever method be used, even if reattachment of the retina be obtained.
Instruments. Speculum, fixation forceps, Graefe’s knife.
Operation. Under cocaine. If no special position be indicated the puncture is best made upwards and inwards. The patient is made to look outwards and downwards. The conjunctiva over the sclerotic, well behind the ciliary body, is drawn down so that when released it shall form a valvular opening to the scleral wound. The Graefe’s knife is driven through the conjunctiva and sclerotic, the incision being made antero-posteriorly in the direction of the fibres of the sclerotic to avoid wounding the choroidal vessels. It is probably better to enlarge the wound when withdrawing the knife than to turn the latter at right angles before it is withdrawn, as has been recommended by some surgeons. A bead of vitreous usually escapes under the conjunctiva. If the tension be not lowered, gentle massage of the globe through the lid should be employed.