History
In acute angle closure (AAC), the intraocular pressure (IOP) rises rapidly, and the patient may present with dramatic symptoms, including the following:
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Sudden onset of severe ocular pain, redness, blurry vision, headache, and nausea and vomiting
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Patients may complain of seeing haloes around lights. Haloes and blurry vision result from corneal edema.
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The attack may have been precipitated by pupillary dilation, which may result from activities such as going to a movie theater, taking over-the-counter medications that contain antihistamine for cold or allergy, or using dilating eye drops as part of an ophthalmic examination.
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Patients with AAC may be extremely uncomfortable and distressed.
Some patients experience intermittent episodes of partial angle closure and relatively elevated IOP without experiencing a frank attack of AAC. These patients may report incidents of mild pain with slightly blurred vision or may report seeing haloes around lights. Some may be completely asymptomatic. Symptoms can resolve spontaneously if the angle reopens on its own.
Physical
A complete ophthalmic examination should be conducted in patients who present with suspected AAC. This examination should emphasize vision, pupil, gonioscopy, tonometry, slit-lamp examination, and optic nerve evaluation:
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Diagnosis of AAC is based on gonioscopic visualization of an occluded anterior chamber angle in the affected eye and predisposing angle configuration (narrow occludable angle) in the contralateral unaffected eye.
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Tonometry demonstrates an elevated IOP, which may be as high as 40-80 mm Hg.
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Slit-lamp examination may reveal conjunctival injection, a fixed or sluggish and mid-dilated pupil, a shallow anterior chamber, corneal epithelial edema and bullae, and cells and flare. The patient may be sensitive to light, and the eye may be tearing and closed.
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Ophthalmoscopy may reveal a swollen optic disc in an acute attack or excavation if episodes have been chronic or repetitive. Unilateral involvement and worsening symptoms are common in AAC.
If previous episodes of angle closure have occurred, the following may be visible:
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Posterior and peripheral anterior synechiae adhesions between the lens and iris and between the iris and trabecular meshwork
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Glaucoma flecks (vesicles on the anterior subcapsular lens)
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Atrophy of the iris (thinning and whitening of the iris)
Causes
Pupillary block is considered to be the most common cause of AAC. Normally, aqueous humor is made by the ciliary body and flows through the pupil to the anterior chamber, where it drains out of the eye through the trabecular meshwork and the Schlemm canal. If contact occurs between the lens and the iris, aqueous humor accumulates behind the pupil, increasing posterior chamber pressure and forcing the peripheral iris to shift forward. The forward movement of the iris does not cause angle closure in individuals with normal anatomy.
The trabecular meshwork is located between the iris and cornea, and the two structures form an angle that is normally 40°. Persons with susceptible anatomy have a narrow occludable angle, usually of less than 20°. When the iris is pushed forward by the aqueous humor in a narrow occludable angle, it becomes apposed to the trabecular meshwork. This blockage causes accumulation of aqueous humor in the anterior chamber and an acute rise in IOP.
Not all individuals with narrow occludable angle develop AAC, and mechanisms other than pupillary block play a role in development of AAC.
Plateau iris is a condition in which the iris is inserted more anteriorly into the ciliary body and the periphery of the iris is flat. The angle is narrow owing to the anterior iris insertion, and the flat iris bunches up to obstruct the angle when the eye is dilated. [6, 7]
Several medications have been implicated in causing acute ACC by producing swelling in the ciliary body and forward movement of the iris. Sulfa-derivative medications, including acetazolamide, sulfamethoxazole, and hydrochlorothiazide, and antiepileptic medication topiramate have been reported to cause acute attacks. [8, 9]
Persons of Asian descent have thicker irides, and increased iris thickness is associated with angle closure. [10, 11]
Pupillary dilation normally results in loss of iris volume, but this volume decrease is less in eyes that have had AAC; some of these eyes actually showed an increase in iris volume. [12, 13]
Individuals with hyperopia have smaller eyes, and the diameter of the eye (axial length) is shorter. The intraocular structures are spaced closer together. These patients are more likely to have shallow anterior chambers and narrow occludable angles. [1, 2, 3]
Lens volume increases with age and can decrease the amount of space in the anterior chamber via mass effect. [1, 2, 3]
Complications
Loss of vision or blindness can occur without prompt treatment.
