Acute angle-closure glaucoma is a medical emergency characterized by a sudden increase in intraocular pressure (IOP). This condition occurs when the aqueous humor, the fluid in the front part of the eye, is abruptly blocked from its drainage pathway. Unlike more common forms of glaucoma that develop slowly, this acute form progresses rapidly over hours. Failing to seek immediate medical care can lead to optic nerve damage and permanent vision loss.
Symptoms of an Acute Attack
The onset of an acute glaucoma attack is rapid, causing intense pain centered in one eye that may radiate to the forehead. This severe pressure can also trigger systemic responses, including feelings of nausea and vomiting.
Vision in the affected eye may become very blurry or hazy. A distinct symptom is the appearance of halos or rainbow-colored rings when looking at lights. This is caused by swelling of the cornea, which scatters light as it enters the eye.
Physical changes are also apparent during an attack. The white of the eye often becomes red, and the clear cornea may appear hazy or cloudy. The pupil of the affected eye might become enlarged and not react properly to light.
Causes and Risk Factors
Acute angle-closure glaucoma is caused by a physical blockage of the eye’s primary drainage system, the trabecular meshwork. The obstruction occurs at the angle where the iris meets the cornea. When this angle narrows or closes, aqueous humor is trapped, causing intraocular pressure to rise rapidly.
Individuals who are farsighted or have a shallow anterior chamber are at higher risk because the space for fluid drainage is restricted. As people age, the eye’s natural lens thickens, which can push the iris forward and narrow the drainage angle. This explains why the condition is more prevalent in individuals over 40.
The condition is more common in women and has a higher prevalence among people of Asian and Inuit descent. A family history of angle-closure glaucoma also indicates an inherited risk. Certain medications can trigger an attack in susceptible individuals by causing the pupil to dilate, including some antidepressants, antihistamines, and drops used for eye examinations.
Emergency Diagnosis and Immediate Treatment
In an emergency setting, providers confirm the diagnosis by measuring intraocular pressure with tonometry. During an attack, pressure can reach 60 to 80 mm Hg, far above the normal 10 to 20 mm Hg range. A specialist will also perform gonioscopy, using a special contact lens to visualize the drainage angle and confirm its closure.
The immediate goal of treatment is to lower the high intraocular pressure to prevent optic nerve damage. This is achieved with medications administered as eye drops and orally or intravenously. Beta-blocker eye drops reduce the production of aqueous humor, while miotics like pilocarpine constrict the pupil, which helps pull the iris away from the drainage angle.
Systemic medications are also used to bring the pressure under control. Oral or intravenous drugs, such as acetazolamide, rapidly decrease the eye’s fluid production. These emergency treatments stabilize the eye and are a temporary measure before a permanent solution is implemented.
Long-Term Management and Prevention of Future Attacks
After emergency stabilization, a long-term treatment is needed to prevent future attacks. The most common solution is a laser peripheral iridotomy (LPI). In this outpatient procedure, an ophthalmologist uses a laser to create a tiny hole in the outer edge of the iris.
This small opening provides a new, permanent channel for the aqueous humor to flow from the posterior to the anterior chamber. This new route bypasses the pupillary block, equalizes pressure between the chambers, and allows the iris to fall back from the drainage angle, preventing it from closing again.
Because the risk is determined by the eye’s anatomy, the unaffected eye is also at risk. An ophthalmologist will recommend a prophylactic laser iridotomy on the other eye as a preventative measure. If LPI is not sufficient, a surgical iridectomy or cataract surgery may be considered. Removing the eye’s natural lens during cataract surgery creates more space and permanently deepens the drainage angle.