Vitreous Prolapse and Lens Injury

Abstract

During trabeculectomy, when a sclerostomy and iridectomy are performed, the structures immediately posterior to the iris, namely the zonules, lens capsule, ciliary processes, and anterior hyaloid face may be violated, resulting in a variety of intraoperative and postoperative complications. Lens injury, including cataract formation, and vitreous prolapse are 2 of the complications that may occur intraoperatively. Cataract formation is one of the most common occurrences after trabeculectomy, reported in approximately 50% of cases. While development of the cataract is usually a slow process, it occurs more frequently in patients with a history of diabetes, postoperative flat anterior chambers, or intraocular inflammation, as well as in a patient with a negative spherical equivalent (preoperative lens status) and pseudoexfoliation syndrome. Older age is a risk factor, since natural cataract development may be accelerated; however, cataracts may develop in up to 25% of younger (<55 years of age) patients undergoing trabeculectomy. The utilization of postoperative steroids has also been implicated in the development of posterior subcapsular opacities. Although not a common occurrence, cataracts may also develop soon after surgery due to direct intraoperative surgical trauma to the lens. If the opacity is focal and does not encroach on or obstruct the visual axis, no further action may be needed. If there is obvious rupture of the lens capsule causing clinically significant inflammation that may compromise bleb development, urgent lens extraction should be performed. If the clinical situation permits, it is desirable to wait at least 3 months until the bleb matures. Rapidly forming cataracts may also develop due to prolonged contact between the lens and the cornea, such as occurs intraoperatively if forceps inadvertently indent the cornea while retracting the conjunctiva during a limbus-based trabeculectomy. Similarly, the lens may opacify if the anterior chamber is flat for an extended period of time before the scleral flap sutures are adequately tied. Likewise, postoperative hypotony with a flat anterior chamber may lead to cataract formation (see Chapter 10).