Trocar placement for pars plana–assisted anterior vitrectomy. a. A point 3 mm posterior to the limbus is marked with the caliper that is included on the trocar. Note that an infusion cannula has already been placed through a limbal wound. b. The lancet is placed through the conjunctiva and engages the sclera at an angle; it is advanced with constant pressure. c. After a short (1–2 mm) shelved incision is made, the trocar is pointed toward the optic nerve and d. quickly punctures the scleral wall. The lancet can then be removed, and the trocar is ready for use.