Fig. 17. Trabeculotomy. A. After development of a limbus-based conjunctival flap, a small scleral flap approximately two thirds of the thickness of the sclera is made. B. The underlying sclera is incised, with care taken to watch for leakage of aqueous and search for Schlemm'canal. C. A suture is threaded into Schlemm's canal, and its position is verified. D. The McPherson's trabeculotome is threaded into Schlemm's canal. E. Gonioscopic view showing the trabeculotome in the proper position. F. With the plane of the trabeculotome parallel to the iris, the handle is rotated so that the tip is torn through the trabecula into the anterior chamber. G. After the tip has entered the anterior chamber, the trabeculotome is withdrawn and the chamber reformed. (Spaeth GL. Glaucoma surgery. In Spaeth GL (ed). Ophthalmic Surgery: Principles and Practice. Philadelphia: WB Saunders, 1990.)