Aqueous humor is released by the ciliary body and normally flows between the lens and the iris, then through the pupil, into the anterior chamber where it is absorbed by a trabecular meshwork and the canal of Schlemm (sinus venosus sclerae) at the angle between the cornea and the iris.
Angle-closure glaucoma (also called narrow angle glaucoma) occurs in patients with a shallow anterior chamber angle. With age, the lens enlarges and especially so with cataract development, restricting the flow of aqueous humor to the drainage site, particularly in farsighted people (ie, with short ocular axial lengths). Fluid can build up behind the lens and iris, pressing the lens and iris into contact, forcing the iris forward, further narrowing or blocking the drainage channel (angle), with a resulting rapid rise in intraocular pressure.
Angle-closure glaucoma can be classified as subacute (intermittent angle closure with spontaneous resolution), acute (sudden blockage of aqueous outflow by the iris), or chronic (with permanent occlusion of portions of the angle by peripheral anterior synechiae or apposition of the iris).
Angle-closure glaucoma affects less than 10% of patients with glaucoma, is often inherited, occurs most commonly in farsighted elderly people (especially women), and often affects both eyes.
Patients with subacute angle closure have intermittent episodes of elevated intraocular pressure lasting minutes to hours, that may present with headache.
Symptoms of angle-closure glaucoma
Signs of angle-closure glaucoma
The International Classification of Headache Disorders (Headache Classification Subcommittee of the International Headache Society 2004) diagnostic criteria for headache attributed to acute glaucoma (11.3.1) are:
Shindler and colleagues identified 11 patients with gonioscopic evidence of intermittent angle closure who had headaches as their chief complaint, from among 2227 patients with headache at a university ophthalmology department between 1996 and 2004 (Shindler et al 2005). Shindler and colleagues reviewed headache histories, ocular examination findings, and effects of laser peripheral iridotomy treatment on headache symptoms (Shindler et al 2004). The average age of cases was 54 years. Headaches had been present for an average of 2.6 years. Headaches were frequent and brief. Most patients reported daily headaches that lasted from minutes to several hours, but none lasted more than 4 hours. Headaches were most commonly described as a mild to moderate aching (ie, non-throbbing) behind 1 eye or hemicranially, without associated nausea, photophobia, or aggravation by activity. Only 4 patients had associated visual blurring or halos around lights (although patients with a primary complaint of blurred vision or ocular pain were excluded). About two thirds (7 of 11) were misdiagnosed as migraine. Ten patients had sequential, bilateral laser peripheral iridotomy, and all experienced improvement (4 cases) or resolution (6 cases) of their headaches.
Angle-closure glaucoma should be considered in the differential diagnosis of any patient with new-onset headache developing after age 50, especially with an acute red eye and reduced vision, but also with short-duration headaches (4 hours or less) that do not meet criteria for a defined headache syndrome. Some patients with angle-closure glaucoma may have headache in the absence of significant eye pain, abnormal appearance of the eye, or visual symptoms, and some patients with angle-closure glaucoma have associated nausea and vomiting, making the distinction between primary headache syndromes difficult (Lewis and Furman 1998; Nesher et al 2005). Although subacute angle-closure glaucoma is often confused with primary headache syndromes, most patients do not meet standard criteria for primary headache syndromes.
Angle-closure glaucoma is essential to recognize because:
The penlight test is a very helpful screening test to help recognize a narrow anterior chamber depth. The penlight is used to tangentially illuminate the pupil from the lateral side. Normally the illumination will involve the entire iris, but with an abnormally narrow anterior chamber the iris is bowed forward and the nasal iris is in shadow (not illuminated). A positive penlight test has high specificity for narrow angles, but a sensitivity of less than 30%. Gonioscopy by an ophthalmologist is the definitive test for determining anterior chamber depth.
Patients with suspected subacute or acute angle closure should be emergently evaluated by an ophthalmologist.
Acute angle closure is a medical emergency that can produce permanent visual loss in a matter of hours. Acute angle closure is initially treated with topical miotics (eg, pilocarpine 2%), beta blockers (eg, timpotic 0.5%), and alpha-adrenergic agonists (eg, apraclonidine 1%), in conjunction with oral or intravenous carbonic anhydrase inhibitors (eg, acetazolamide 500 mg by mouth or IV) and hyperosmotics (eg, glycerin or mannitol). Pilocarpine narrows the pupil and pulls the peripheral iris away from the trabecular network involved in draining aqueous humor.
A laser iridotomy creates an opening in the iris to allow the aqueous humor to move more easily to the drainage site. Because the risk of binocular involvement is high, the procedure is usually done on both eyes, even if only 1 eye is initially symptomatic. Laser iridotomy will prevent further attacks of acute glaucoma, but some individuals with chronic angle closure will still have slightly high intraocular pressures, and will require eye drops indefinitely. Some patients will require peripheral iridectomy (ie, surgical removal of a section of the peripheral iris). Cataract surgery can also prevent attacks of acute narrow angle glaucoma.