Handbook of Ocular Disease Management

PRIMARY CHRONIC ANGLE CLOSURE GLAUCOMA

Signs and Symptoms

The patient with primary chronic angle-closure glaucoma (CACG) typically is older and asymptomatic.¹ Women are more commonly affected than men. Hyperopia is commonly encountered. Patients of Asian descent are the most predisposed to CACG, with Eskimos being the most represented group with CACG. Caucasian patients are affected to a lesser extent, and patients of African descent are affected even less.

Biomicroscopically, there will be a shallow anterior chamber and narrow angles by Von Herrick estimation method. However, the chamber depth is typically deeper in CACG than primary acute angle-closure glaucoma. There will be characteristic glaucomatous damage to the optic disc and visual field. The distinguishing characteristic is the absence of visible anterior chamber angle structures upon the performance of gonioscopy. The angle may be appositionally closed and opened upon manual pressure on the 4-miror goniolens, or the angle may be synechially closed with broad areas of peripheral anterior synechia (PAS). The superior and temporal quadrants of the anterior angle may be the earliest sites of the synechial angle closure, with gradual extension to the nasal quadrant, until the angle closes at the inferior quadrant.² Other features of CACG include a smaller corneal diameter, shorter axial length, shallower anterior chamber, thicker lens, more relative anterior location of the lens, swelling of the ciliary process and anterior rotation of the ciliary body.³

Pathophysiology

Anatomical features act in concert to cause shallowing of the anterior chamber. As a patient ages, thickening of the crystalline lens leads to a relative pupil block that exacerbates the condition. This all acts to put the iris into apposition with the trabecular meshwork or cornea. In the absence of secondary causes, this is considered to be a primary angle closure. Due to the fact that the closure is slow, there is an absence of symptoms that would typify an acute angle closure. Thus, patients are unaware of the process. Chronic angle closure denotes an angle with areas that are closed permanently with PAS. In angles that have closure without the formation of PAS, the term chronic appositional closure is often used. However, appositional closure often will lead to PAS if untreated. In chronic angle closure, the intraocular pressure (IOP) may be initially low and elevates asymptomatically as more of the angle becomes compromised. Peripheral anterior synechia may occur after acute or subacute attacks of angle closure.

While in most cases, there is asymmetric closure involving first the superior angle, there can also be an even circumferential closure that slowly progresses symmetrically. This has been termed "creeping angle closure" and appears as an angle that becomes progressively more shallow over time.⁴

Management

All cases of primary angle closure need to undergo laser peripheral iridotomy (LPI) as soon as possible after diagnosis. This allows a communication for aqueous to flow from the posterior chamber to the anterior chamber bypassing any pupil block that may be present. This can allow for the backward relaxation of the iris and a deepening of the chamber and opening of the angle. This is a safe method to open the angle following chronic closure.⁵ However, while LPI can alter the anatomic status of the angle, there often will be elevated IOP despite a laser-induced open anterior chamber angle. This is most likely due to damage to the trabecular meshwork from appositional and synechial closure. In CACG eyes, the trabecular architecture has lost its regular arrangement, with fewer and narrower trabecular spaces and fusion of the trabecular beams in areas. In addition, there is evidence of loss of endothelial cells and reactive repair processes.⁶ Despite the presence of a patent LPI, most eyes with CACG presenting with elevated IOP and having both optic disc and visual field damage in both populations required further treatment to control IOP, including trabeculectomy and medical therapy.⁷ Medical therapy that has been seen to be successful in ameliorating the IOP in eyes with CACG include beta blockers, miotics, alpha-2 adrenergic agonists, and prostaglandins.^8,9 Argon laser iridoplasty has been seen as another option for the management of CACG as it can affect the shape of the peripheral iris and prevent this condition from deteriorating.¹⁰

Clinical Pearls

After the anterior chamber angle has been successfully opened by LPI, the IOP may still be elevated. Many will erroneously think that the patient has now developed primary open-angle glaucoma. In actuality, the trabecular meshwork has been damaged by the appositional closure. This situation is like the trabecular dysfunction seen in angle-recession glaucoma.
Gonioscopy must be done on all open angle glaucoma patients at least annually to ascertain that the patient is not developing a concurrent angle-closure mechanism.

Bonomi L, Marchini G, Marraffa M, et al. Epidemiology of angle-closure glaucoma: prevalence, clinical types, and association with peripheral anterior chamber depth in the Egna-Neumarket Glaucoma Study. Ophthalmology. 2000;107(5):998-1003.
MOK KH, Lee VW. Synechial angle closure pattern in Chinese chronic primary angle-closure glaucoma patients. J Glaucoma. 2001;10(5):427-8.
Wang T, Liu L, Li Z, et al. Studies of mechanism of primary angle closure glaucoma using ultrasound biomicroscope. Zhonghua Yan Ke Za Zhi. 1998;34(5):365-8.
Lowe RF. Primary creeping angle closure glaucoma. Br J Ophthalmol 1964;48:544.
Hsiao CH, Hsu CT, Shen SC, et al. Mid-term follow-up of Nd:YAG laser iridotomy in Asian eyes. Ophthalmic Surg Lasers Imaging. 2003;34(4):291-8.
Sihota R, Lakshmaiah NC, Walia KB, et al. The trabecular meshwork in acute and chronic angle closure glaucoma. Indian J Ophthalmol. 2001;49(4):255-9.
Rosman M, Aung T, Ang LP, et al. Chronic angle-closure with glaucomatous damage: long-term clinical course in a North American population and comparison with an Asian population. Ophthalmology. 2002;109(12):2227-31.
Ruangvaravate N, Kitnarong N, Metheetrairut A, et al. Efficacy of brimonidine 0.2 per cent as adjunctive therapy to beta-blockers: a comparative study between POAG and CACG in Asian eyes. J Med Assoc Thai. 2002;85(8):894-900.
Aung T, Wong HT, Yip CC, et al. Comparison of the intraocular pressure-lowering effect of latanoprost and timolol in patients with chronic angle closure glaucoma: a preliminary study. Ophthalmology. 2000;107(6):1178-83.
Zou J, Zhang F, Zhang L, et al. A clinical study on laser peripheral iridoplasty for primary angle-closure glaucoma with positive provocative tests after iridectomy. Chung Hua Yen Ko Tsa Chih. 2002;38(12):708-11.

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