Reply: Managing iris prolapse

Abstract

We agree with most of Hu and Hou's management strategies for intraoperative iris prolapse but would like to make a few additional points. In cases of actual and potential iris prolapse, it is important to identify the mechanisms of prolapse and to address these factors. In cases in which iris prolapse may pose a problem, such as patients with shallow anterior chambers, preoperative planning is essential. It is important to place the main incision within clear cornea rather than at the limbus and to combine this with a longer tunnel before entry into the anterior chamber.1 However, if iris prolapse occurs, it is important to reposition the iris and reduce the risk for further prolapse. The OVD may be used to achieve this. As Hu and Hou highlighted, it is important not to overfill the anterior chamber with OVD, as the high anterior chamber pressure and the high OVD viscosity can result in reprolapse of the iris. We think a better approach is to place OVD in the anterior chamber via the main incision to reposition the iris and simultaneously relieve pressure in the anterior chamber; releasing OVD via the side port using a Rycroft cannula results in flow of OVD from the main incision into the anterior chamber and out through the side port, carrying the prolapsed iris back into the anterior chamber. Once the iris has been repositioned, it is important to reduce the amount of pressure change and flow in the anterior chamber. This can be achieved by reducing the bottle height and using bimanual I/A, which maintains a closed anterior chamber and stable pressure. The coaxial I/A is thinner and does not fit the main wound precisely; consequently, the flow from the anterior chamber to the outside results in prolapse of the iris through the main incision. This can be overcome by the use of the bimanual I/A. At the end of surgery, we do not routinely hydrate the incision. However, if the incision is leaking, we recommend the use of sutures or hydration. Acetylcholine can be used to constrict the pupil and move it away from the main incision, reducing the risk for further prolapse. When hydrating the incision, it is important to ensure the cannula tip is in the corneal stroma and not too much fluid is injected into the anterior chamber, as this will increase the pressure and potentially result in prolapse. As indicated in our article, the use of a single subincisional iris retractor functions as a physical barrier against prolapse and pressure changes in the anterior chamber and any vigorous irrigation should not cause prolapse. Hu and Hou mention the use of air to tamponade the iris and prevent prolapse; they also recommend posturing the patient face down. We have never practiced this and would strongly advise caution with this method. The use of an air bubble, especially in the face- down position, may result in pupil block with subsequent rise in intraocular pressure.2 An additional strategy that can be used in cases of potential iris prolapse is to place the main incision superiorly rather than temporally. Although a superior corneal tunnel is closer to the visual axis than a temporal tunnel, the anterior chamber is deeper superiorly than temporally.3 Moreover, should repeated iris prolapse occur with loss of iris pigment epithelium, the risk for iris defects causing monocular diplopia is reduced by the superior approach because of coverage by the upper lid.4