Acute Angle-Closure Glaucoma

Excerpt

Glaucoma, characterized by increased intraocular pressures (IOP), can result in optic neuropathy and vision loss if left untreated. It is classified as open-angle or closed-angle and can be primary or secondary depending on the obstruction in the anterior chamber. The angle refers to the space between the iris and the cornea in the anterior chamber, which can become structurally obstructed.

Primary glaucomas are not associated with known ocular or systemic disorders and usually affect both eyes. In contrast, secondary glaucomas are often unilateral and linked to ocular or systemic diseases. Acute closed-angle glaucoma (ACAG) is a subset of primary angle-closure glaucoma. Acute angle-closure (AAC) is an ophthalmologic emergency with elevated IOP, posing a risk of irreversible damage and potential blindness not treated promptly.

AAC usually presents with significant and distressing symptoms such as unilateral intense periocular pain, redness in the eye, rapid vision loss, systemic symptoms, nausea, headache, multicolored halos around light sources, and vomiting. Nonophthalmologic practitioners may misinterpret these symptoms as neurological conditions, leading to unnecessary cranial imaging and neurologic consultations before ophthalmologic examinations are conducted.

The diagnosis of AAC is confirmed by elevated IOP measured using tonometry, which can range from 50 to 80 mm Hg. Examination with a slit-lamp microscope usually reveals a shallow anterior chamber, corneal edema, fixed dilated pupil, conjunctival injection around the limbus (ciliary flush), and a closed angle on gonioscopy. Treatment options include medical, laser, and surgical interventions to reduce IOP, relieve acute symptoms, and prevent future angle closures.

The normal range for IOP measured by tonometry is 10 to 21 mm Hg. IOP is influenced by the ciliary body's production rate of aqueous humor, the resistance to aqueous outflow through the trabecular meshwork and Schlemm's canal, and the episcleral venous pressure. Aqueous humor is produced in the ciliary body, passes through the pupil, and drains through the trabecular meshwork (TM) and Schlemm canal at the anterior chamber's angle. In ACAG, IOP increases rapidly due to outflow obstruction of the aqueous humor. The main predisposing factor for ACAG is the anterior chamber's structural anatomy, which can lead to a shallower angle.