Abstract

Glaucoma filtering surgery is an effective method to lower intraocular pressure (IOP).However, as is the case with any interventional procedure, filtering surgery poses risks to the eye. At a reported incidence of 4.2%–10%, late leakage of filtering blebs is one of the most common and challenging complications encountered by glaucoma surgeons Bleb leaks pose many sight-threatening risks to the eye, including inflammation, blebitis, endophthalmitis, hypotony with its attendant risk of choroidal effusions and maculopathy, flat chamber with corneal decompensation, cataractous changes, and suprachoroidal hemorrhage. Additionally, allowing bleb leaks to persist risks failure of the filtration surgery. Leaks can occur at any point in the life of the bleb, from months to years after surgery, and late bleb leaks are commonly referred to as those occurring at least 2 months after surgery. Unlike early bleb leaks, which are frequently located at incisions and suture tracks or are secondary to intraoperative surgical trauma (buttonholes), late bleb leaks can often be seen at the apex of a cystic, avascular bleb (Figure 16.1). These leaks arise from focal epithelial thinning, which eventually culminates in a conjunctival defect in the wall of the bleb. Bleb leaks occur for a variety of reasons, including trauma to the conjunctival bleb wall. Thin-walled, focal, cystic blebs are at a much greater risk of leaking than diffuse, vascular blebs. One important risk factor for development of thin-walled blebs is the use of antifibrotic agents, such as 5-fluorouracil and mitomycin-C (see Chapter 27). Mechanical factors, such as eye rubbing, contact lenses, and giant papillary conjunctivitis, also increase the risk of bleb leaks by causing trauma to a focal area of susceptible conjunctiva. Although digital ocular compression is frequently performed and prescribed by ophthalmologists for management of encapsulated filtering blebs, one study from Japan showed that there is an increased risk of leak (3.1%–5.6%) with digital ocular bleb compression. This risk was especially increased in blebs with a larger avascular area or a longer intraoperative duration of mitomycin-C. In addition, conditions that cause conjunctival exposure, such as thyroid ophthalmopathy or a large overhanging bleb, can also increase the chances of leakage.

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