Scleral Perforation

Abstract

Scleral perforation during tube shunt implantation is a rare complication. In a recent publication of the Tube Versus Trabeculectomy Study, 3 out of 107 patients in the tube shunt group had scleral perforation during placement of a device. Merino-de-Palacios et al reported scleral perforation during tube shunt surgery in 1 of 86 eyes. The type of device used does not seem to be important in the incidence of scleral perforation. In the Tube Versus Trabeculectomy Study, Baerveldt® devices (Abbott Medical Optics, Inc., Santa Ana, California) were used exclusively, and Ahmed™ Glaucoma Valves (New World Medical, Inc., Rancho Cucamonga, California) and Molteno® implants (Molteno Ophthalmic, Ltd., Dunedin, New Zealand) were used in the study by Merino-de-Palacios et al. Serious sequelae, such as endophthalmitis or retinal detachment, have not been reported in recent literature following scleral perforation during tube shunt placement; nonetheless, this complication should be prevented and, if it does occur, managed promptly. Patients who are believed to have an increased risk for scleral perforation are myopic patients (>-6.00 D) and patients with previous extraocular muscle surgery. Patients with previous scleral buckle surgery, autoimmune diseases, scleritis, or any other conditions that cause or perpetuate thinning of the sclera potentially increase the risk. Patients with previous scleral buckling procedures who require tube shunt surgery will benefit from having the device anchored behind the buckle or directly over the buckle. No attempt should be made to dissect under the buckling device, as dissection may lead to the buckle anchoring sutures perforating the eye. The most common site for tube shunt implantation is the superotemporal quadrant, between the superior and lateral rectus muscles. This location offers the benefit of having the implant hidden under the superior eyelid, no oblique muscles in the region, and better intraoperative exposure, allowing the surgeon to place the implant farther from the limbus. The plate of the implant is usually attached to the sclera approximately 8–10 mm posterior to the limbus. This is also the thinnest portion of the sclera. Exposure when implanting the tube shunt is probably the most important factor in avoiding scleral perforation.