Malignant Glaucoma (Posterior Aqueous Diversion Syndrome)

Abstract

The term malignant glaucoma has been used historically to describe a devastating and unusual form of glaucoma that occurred following ocular surgery. The current definition has been expanded to include classic malignant glaucoma and nonphakic malignant glaucoma as well as disorders occurring in other clinical situations. Classic malignant glaucoma is usually associated with a specific clinical scenario that occurs after incisional surgery (iridectomy or filtration) for primary angle-closure glaucoma, secondary or chronic angle-closure glaucoma, or at times open-angle glaucoma in phakic patients. The occurrence of malignant glaucoma after cataract surgery and the persistence of malignant glaucoma following cataract surgery in the classic form have been termed as aphakic malignant glaucoma. The diagnosis nonphakic malignant glaucoma has been suggested for both aphakic and pseudophakic types and may also be applied to the development of malignant glaucoma after combined cataract and filtration surgery. The term malignant-like glaucoma has been proposed for instances with similar clinical presentations but where different underlying pathophysiology may be present. The pathognomonic findings of classic malignant glaucoma are increased IOP or unexpected normal IOP following glaucoma surgery, central (axial) shortening of the anterior chamber, open iridotomy or iridectomy, and no evidence for choroidal effusion or hemorrhage. Classic malignant glaucoma typically develops after surgical peripheral iridectomy or filtering (full-thickness sclerectomy or trabeculectomy) surgery in phakic patients. Two clinical cases discussed here are illustrative of classic malignant glaucoma presentations. Malignant glaucoma in aphakia is a term for eyes with persistence of preexisting malignant glaucoma after cataract surgery as well as in patients with malignant glaucoma occurring following routine cataract surgery. Malignant glaucoma has also been reported following Nd:YAG laser capsulotomy, diode laser cyclocoagulation, and aqueous tube shunt surgery. Numerous clinical entities share some or all the findings of classic phakic and nonphakic malignant glaucoma. The presence of diagnostic criteria and the response to treatment distinguish between malignant glaucoma and malignant-like glaucoma. The clinical findings in malignant glaucoma and its various presentations previously have been thought to be primarily the end result of aqueous misdirection or posterior aqueous diversion. Mechanisms that involve various contributions of the lens or zonules, ciliary processes, anterior hyaloid face, or vitreous body have been proposed. Malignant glaucoma would result from a persistent expansion of the vitreous volume in an eye with a relatively impermeable and diminished anterior hyaloid surface rather than from isolated pools of trapped aqueous in the vitreous cavity. The final common pathway of the various contributing mechanisms in malignant glaucoma is a self-perpetuating expansion of the vitreous. Epstein has brought these mechanisms together into what he terms “unifying concepts in malignant glaucoma.” Quigley subsequently hypothesized that choroidal expansion is the inciting event leading to increased vitreous pressure. The enlarged vitreous body can no longer exchange aqueous at the level of the hyaloid face, zonules, and ciliary processes. This pushes the iris forward from behind, flattening the central and peripheral anterior chamber, increasing iridotrabecular apposition, and elevating intraocular pressure in a vicious cycle. Malignant glaucoma usually presents as a postoperative flat central anterior chamber in an eye with normal or elevated IOP. The diagnoses that it is most commonly confused with are pupillary block, choroidal effusion, and suprachoroidal hemorrhage. UBM is a valuable tool in the differential diagnosis of pupillary block, secondary angle closures, suprachoroidal effusion, suprachoroidal hemorrhage, and the malignant glaucoma-like syndromes. The medical and surgical management of malignant glaucoma has greatly improved with advances in our understanding of the pathophysiologic mechanisms of this disease and current treatment options. Medical therapy has been reported to be curative in 50 % of patients within 5 days. Argon laser treatment of the ciliary processes, with or without adjunctive medical therapy, has been advocated for phakic and aphakic malignant glaucoma. In pseudophakic patients it is necessary to create an open communication between the posterior and anterior segment with laser treatment to the lens capsule and residual lens material, if necessary, in addition to the vitreous face. When medical or laser therapy is not successful in relieving malignant glaucoma, vitreous surgery is indicated. Automated mechanical vitrectomy through a posterior sclerotomy in phakic eyes or through a limbal approach in nonphakic eyes is currently a preferred alternative to the manual method and is often curative. After an episode of malignant glaucoma in one eye, the risk of malignant glaucoma in the contralateral eye is significant if surgery is needed after an acute angle-closure attack. Over the years, our better understanding of the pathophysiology coupled with improvements in our diagnostic, medical, and surgical armamentarium have allowed clinicians to make an accurate diagnosis and promptly institute effective treatment.