Primary and Secondary Angle-Closure Glaucomas

Abstract

Almost 70 million cases of glaucoma have been diagnosed worldwide, approximately half of which are classified as angle-closure glaucoma (ACG). Among patients with angle closure, primary angle-closure glaucoma (PACG) is the most common diagnosis. Angle closure results from apposition of the peripheral iris to the trabecular meshwork (iridotrabecular contact – ITC). Four current methods for diagnosing the classification of angle-closure glaucoma are presented. The individual with an anatomically narrow angle can be classified as a primary angle-closure suspect (PACS) when gonioscopy reveals a shallow peripheral angle recess with the iris close to the trabecular meshwork. In an acute primary angle-closure attack, there is a sudden obstruction of the anterior chamber (AC) angle with an acute elevation of the intraocular pressure to very high levels. In chronic PACG, the angle usually closes gradually over time. The natural history of asymptomatic progression to blindness may be analogous to POAG. The possibility to visualize the anterior segment structures with imaging techniques such as ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) has enhanced our ability to better anatomically classify the angle-closure glaucoma, determine the mechanisms involved, and institute proper therapy. Plateau iris configuration and plateau iris syndrome are conditions that are often confused with pupillary block and PAC. Laser peripheral iridoplasty can open the angle in plateau iris syndrome. Conditions classified as secondary angle-closure glaucoma are associated with other ocular or systemic abnormalities. Gonioscopy is essential to identifying the underlying anatomy and pathophysiology of angle closure in order to properly classify the type of glaucoma and initiate treatment. Imaging techniques such as ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) have proven to be a useful adjunct to gonioscopy. Pupillary block is the most frequent etiology of angle closure and the underlying mechanism of most cases of PACG. Acute primary angle closure, an “acute glaucoma attack,” results from sudden pupillary block causing a typical symptom complex. The initial treatment for an acute attack of PACG is to lower the intraocular pressure and relieve the pupillary block. Currently, laser iridotomy (yttrium–aluminum–garnet [YAG] or argon laser) is the primary initial treatment for PACG. A newer approach to the management of angle-closure glaucoma is the consideration of cataract extraction. Primary lensectomy, especially when lens opacity is present, has been increasingly established as an effective treatment of primary angle closure either as an isolated procedure, accompanied by goniosynechialysis, or combined with trabeculectomy. Chronic angle closure is a term used for eyes in which the angle gradually narrows without precipitating an acute attack. An open-angle glaucoma patient may narrow then deepen after laser iridotomy but with the pressure remaining elevated, with or without peripheral anterior synechial formation. This condition is termed “combined mechanism” glaucoma or “mixed-mechanism” glaucoma. Various forms of lens-induced “secondary angle closure” with pupillary block have been described. Phacomorphic glaucoma occurs secondary to a large anteriorly displaced lens. In Weill–Marchesani syndrome (microspherophakia), patients are characteristically of short stature with spade-like hands (brachydactyly). Partially or completely dislocated lenses in numerous conditions associated with ectopia lentis can result in secondary angle closure. Marfan syndrome is an autosomal dominant condition with a physical appearance the opposite of Weill–Marchesani associated with lens-related glaucoma. Homocystinuria, an autosomal recessive disease manifesting in a disorder of homocysteine metabolism, is also associated with lens-related glaucoma. Intraocular lenses (IOLs) can cause pseudophakic secondary angle closure when the optic of the anterior chamber lens (ACIOL) implant blocks communication of aqueous between the posterior and anterior chambers. Secondary angle closure may occur without pupillary block. Aqueous misdirection syndrome is also termed posterior aqueous diversion or ciliary block glaucoma. It was originally named malignant glaucoma because of its relentless course and poor response to treatment, until its physiologic mechanisms were better understood. Neovascular glaucoma results from the occlusion of the trabecular meshwork and secondary closure of the angle by fibrovascular membrane formation. Iridocorneal endothelial (ICE) syndrome was termed to encompass a spectrum of abnormalities that share a disorder of the corneal endothelium. Epithelial and fibrous downgrowth are rare surgical complications resulting in secondary angle closure. Inflammation associated with a variety of ocular and systemic conditions can cause trabeculitis or synechia formation with secondary angle closure. Posterior scleritis may result in large uveal effusions resulting in secondary angle closure. Various retinal disorders and treatments can result in secondary angle-closure glaucoma. Primary or secondary uveal effusions can cause a forward displacement of the iris. Central retinal vein occlusion (CRVO) can cause choroidal swelling with secondary closure as can extensive retinal photocoagulation for CRVO or proliferative diabetic retinopathy.

Topiramate (Topamax) systemic medical therapy for epilepsy, migraine, and other neurological conditions is well documented to cause acute bilateral secondary angle-closure glaucoma.

Nanophthalmos is characterized by a short, less than 20 mm axial length eye with a small corneal diameter, large lens, and thick sclera. Continued advances in diagnostics, imaging systems, and therapeutics have revolutionized the management of angle-closure glaucoma.