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The advantages of the external approach for iridectomy have become well recognized; they are especially evident when a shallow anterior chamber makes the incision by puncture and counterpuncture with the Graefe knife difficult and there is danger of injury to the iris, lens and vitreous. Even more than iridectomy, the Lagrange sclerectomy is difficult and has greater liability to operative accidents. These faults can be eliminated by adoption of the external approach, so that the Lagrange linear fistula can be obtained with no more difficulty and danger than attend the trephine operation.
A long horizontal incision is made in the conjunctiva about 8 mm. above the limbus and undermined to expose the sclera down to the limbus. This is the same as is done for the Elliot trephining operation, except that a longer arc of the limbus is exposed, and the cornea is not split (fig. 1 A). An incision