Angle-closure glaucoma is glaucoma associated with a physically obstructed anterior chamber angle, which may be chronic or, rarely, acute. Symptoms of acute angle closure are severe ocular pain and redness, decreased vision, colored halos around lights, headache, nausea, and vomiting. Intraocular pressure (IOP) is elevated. Immediate treatment of the acute condition with multiple topical and systemic medications is required to prevent permanent vision loss, followed by the definitive treatment, iridotomy.
(See also Overview of Glaucoma.)
Angle-closure glaucoma accounts for about 10% of all glaucomas in the United States.
Etiology of Angle-Closure Glaucoma
Angle-closure glaucoma is caused by factors that either pull or push the iris up into the angle (ie, junction of the iris and cornea at the periphery of the anterior chamber), physically blocking drainage of aqueous and raising intraocular pressure (IOP) (see table Angle-Closure Glaucoma). Elevated IOP damages the optic nerve.
Pathophysiology of Angle-Closure Glaucoma
Angle closure may be primary (cause is unknown) or secondary to another condition and can be acute, subacute (intermittent), or chronic.
Primary angle-closure glaucoma
Narrow angles are not present in young people. As people age, the lens of the eye continues to grow. In some but not all people, this growth pushes the iris forward, narrowing the angle. Risk factors for developing narrow angles include family history, advanced age, and race; risk is higher in Asian and Inuit populations and lower in European and African populations.
In people with narrow angles, the distance between the iris at the pupil and the lens is also very narrow. When the iris dilates, forces pull the iris centripetally and posteriorly causing increasing iris–lens contact, which prevents aqueous from passing between the lens and iris, through the pupil, and into the anterior chamber (this mechanism is termed pupillary block). Pressure from the continued secretion of aqueous into the posterior chamber by the ciliary body pushes the peripheral iris anteriorly (causing a forward-bowing iris called iris bombe), closing the angle. This closure blocks aqueous outflow, resulting in rapid (within hours) and severe (> 40 mm Hg) elevation of intraocular pressure (IOP). Nonpupillary block mechanisms include plateau iris syndrome, in which the central anterior chamber is deep but the peripheral anterior chamber is made shallow by a ciliary body that is displaced forward.
Acute angle-closure glaucoma requires immediate recognition and treatment because vision can be lost quickly and permanently.
Intermittent angle-closure glaucoma occurs if the episode of pupillary block resolves spontaneously after several hours, usually after sleeping supine.
Chronic angle-closure glaucoma occurs if the angle narrows slowly, allowing scarring between the peripheral iris and trabecular meshwork; IOP elevation is slow.
Pupillary dilation (mydriasis) can push the iris into the angle and precipitate acute angle-closure glaucoma in any person with narrow angles.
Secondary angle-closure glaucomas
The mechanical obstruction of the angle is due to a coexisting condition, such as proliferative diabetic retinopathy (PDR), ischemic central vein occlusion, uveitis, or epithelial down-growth. Contraction of a neovascular membrane (eg, in PDR) or inflammatory scarring can pull the iris into the angle.
Symptoms and Signs of Angle-Closure Glaucoma
Acute angle-closure glaucoma
Patients have severe ocular pain and redness, decreased vision, colored halos around lights, headache, nausea, and vomiting. The systemic complaints may be so severe that patients are misdiagnosed as having a neurologic or gastrointestinal problem. Examination typically reveals conjunctival hyperemia, a hazy cornea, a fixed mid-dilated pupil, and anterior chamber inflammation. Vision is decreased. Intraocular pressure (IOP) measurement is usually 40 to 80 mm Hg. The optic nerve is difficult to visualize because of corneal edema, and visual field testing is not done because of discomfort. For primary mechanisms of angle-closure (eg, pupillary block and plateau iris), examination of the uninvolved contralateral eye can indicate the diagnosis.
Pearls & Pitfalls
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Chronic angle-closure glaucoma
This type of glaucoma manifests similarly to open-angle glaucoma. Some patients have ocular redness, discomfort, blurred vision, or headache that lessens with sleep (perhaps because of sleep-induced miosis and posterior displacement of the lens by gravity). On gonioscopy, the angle is narrow, and peripheral anterior synechiae (PAS), which are adhesions between the peripheral iris and angle structure causing blockage of trabecular meshwork and/or ciliary body face, may be seen. IOP may be normal but is usually higher in the affected eye.
Diagnosis of Angle-Closure Glaucoma
Acute: Measurement of intraocular pressure (IOP) and clinical findings
Chronic: Gonioscopy showing peripheral anterior synechiae and characteristic optic nerve and visual field abnormalities
Diagnosis of acute angle-closure glaucoma is clinical and by measurement of IOP. Gonioscopy may be difficult to do in the involved eye because of a clouded cornea with friable corneal epithelium. However, examination of the other eye reveals a narrow or occludable angle. If the other eye has a wide angle, a diagnosis other than primary angle-closure glaucoma should be considered. Pupillary block mechanism can be recognized as iris bombe, an anterior bowing or arc of the iris between the angle and the pupil.
Diagnosis of chronic angle-closure glaucoma is based on the presence of peripheral anterior synechiae on gonioscopy and characteristic optic nerve and visual field changes (see symptoms and signs of primary open-angle glaucoma).
Before giving or prescribing mydriatic eye drops (which can trigger acute narrow-angle glaucoma in patients at risk), anterior chamber depth should be assessed. If gonioscopy is unavailable, the chamber depth can be more crudely assessed using a slit lamp or even a penlight; the penlight is held next to the temporal side of the eye, with the light beam parallel to the iris. If a shadow is cast on the nasal iris, the angle is probably narrow, because the temporal iris bows forward and blocks the light.
Treatment of Angle-Closure Glaucoma
Acute:
Chronic: Similar to primary open-angle glaucoma except that laser peripheral iridotomy should be done if the ophthalmologist feels that the procedure may slow mechanical closing of the angle. Cataract removal helps delay the progression of chronic angle-closure glaucoma.
Acute angle-closure glaucoma
> 40 or 50 mm Hg because of an anoxic pupillary sphincter.
Definitive treatment is with laser peripheral iridotomy (LPI), which opens another pathway for fluid to pass from the posterior to the anterior chamber, breaking the pupillary block. It is done as soon as the cornea is clear and inflammation has subsided. In some cases the cornea clears within hours of lowering the IOP; in other cases, it can take 1 to 2 days. Because the chance of having an acute attack in the other eye is 80%, LPI is done on both eyes.
The risk of complications with LPI is extremely low compared with its benefits. Glare, which can be bothersome, may occur.
Chronic angle-closure glaucoma
Patients with chronic, subacute, or intermittent angle-closure glaucoma should also have LPI. Additionally, patients with a narrow angle, even in the absence of symptoms, should undergo prompt LPI to prevent angle-closure glaucoma. If a cataract is present, cataract removal can dramatically delay the progression of chronic angle-closure glaucoma.
The medications and full-thickness incisional surgical treatments used for angle-closure glaucoma are the same as those used for open-angle glaucoma. However, laser trabeculoplasty is relatively contraindicated if the angle is so narrow that additional peripheral anterior synechiae may form after the laser procedure. Typically, partial-thickness procedures are not indicated.
Key Points
Angle-closure glaucoma can develop acutely, intermittently, or chronically.
Suspect acute angle-closure glaucoma based on clinical findings and confirm it by measuring intraocular pressure.
Confirm chronic angle-closure glaucoma by peripheral anterior synechiae and optic nerve and visual field changes.
Treat acute angle-closure glaucoma as an emergency.
Consult an ophthalmologist to arrange laser peripheral iridotomy for all patients with angle-closure glaucoma.
