=Complications.= (1) Unless the incision be carried carefully through the sclerotic, or the manipulations with the iris spatula be very gentle, loss of vitreous is liable to take place. As a rule, this, if not great, is of little consequence. (2) In passing the iris spatula forward to separate the ligamentum pectinatum the point may pass between the layers of the cornea; this is recognized in the resistance offered to the side-to-side movement of the spatula, which should be withdrawn slightly and the point depressed so as to engage the ligamentum pectinatum. (3) Subchoroidal hæmorrhage has been known to occur after the operation. SCLERECTOMY The object of the operation is the production of a filtration cicatrix free from iris tissue for the relief of intra-ocular tension in chronic glaucoma. =Instruments.= As for glaucoma iridectomy, with the addition of a small curved pair of scissors. =Operation.= Under cocaine. _First step._ The incision is performed as for glaucoma iridectomy (see p. 221), except that the incision should be rather smaller and should be carried more obliquely through the sclerotic, so that a long scleral flap is obtained. A large conjunctival flap is very essential to cover the wound. _Second step._ An iridectomy is usually performed as for glaucoma; this may be omitted. _Third step._ After all the bleeding has ceased, the conjunctival flap is turned forwards on to the cornea so as to expose the scleral flap; with small curved scissors made for the purpose, an elliptical portion is removed from the sclerotic by a single snip (Figs. 121 and 122), and the conjunctival flap is replaced in position. As a result, a hole is made into the anterior chamber, which thus communicates with the subconjunctival tissue, which is bulged forwards in the form of a clear vesicle by the escaping aqueous when the wound has healed. [Illustration: FIG. 121. LAGRANGE OPERATION FOR THE PRODUCTION OF A CYSTOID SCAR IN CHRONIC GLAUCOMA. Showing the method of removing a piece of the sclerotic.] [Illustration: FIG. 122. LAGRANGE OPERATION FOR CHRONIC GLAUCOMA. Showing the piece of sclerotic removed by the scissors (black lines).] 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.