Intrinsic to glaucoma surgery using a tube shunt is the management of early postoperative hypotony. This consideration is unavoidable in all cases when using a tube shunt without an intrinsic valve and must still be considered in tube shunts that contain a valve, as the valve may not function as anticipated. Unfortunately, in the attempt to avoid hypotony and its associated complications, we are faced with elevated intraocular pressure (IOP) and its associated difficulties. However, the attempt to control IOP is not the only consideration when anticipating intentional tube occlusion. Additional factors such as technical complexity of the procedure, predictability of IOP in the early postoperative period, potential to reverse occlusion either partially or completely, and the impact on the long-term function of the tube shunt must be considered. The desired endpoint when occluding a tube intentionally is the complete prevention of flow to the tube shunt reservoir. The standard ways to occlude the tube are an external encircling ligature or an internal occluding suture, otherwise known as an “obturator” or a “ripcord,” or some combination thereof. With the external suture technique, prior to placing the reservoir, a 7–0 or 8–0 polyglactin 910 (Vicryl™ , Ethicon, Inc., Somerville, New Jersey) suture is tightly tied around the tube approximately 4–6 mm from the reservoir (Figure 35.1). It is anticipated that this suture will dissolve in about one month, opening the tube. However, the timing of opening may be highly variable between individuals, and that variability may be problematic. Alternatively, a 9–0 polypropylene suture can be placed around the tip of an anterior chamber tube with release performed by laser lysis. To prevent the polypropylene suture from floating freely in the anterior chamber after release, a pass should be made through the wall of the tube during placement. Alternatively, with the “ripcord” technique, the end of a 3–0 polypropylene suture without the needle is threaded into the distal opening of the tube at the reservoir for a distance of 4–6 mm.
Intraocular Pressure Changes after Uneventful Phacoemulsification in Early Postoperative Period in Healthy Eyes