Acute angle closure

Fig. 1A. Clinicaloverviewofprimaryangleclosure.Thisdiagramhelpsunderstandingoftheclinical course of the angle closure. The Y-axis is IOP and the X-axis is time. In IAC the small sub-clinical spikes of IOP elevation occur. Sometimes it develops into a big spike and makes an AAC, while also it may develop into a slow but progressive CAC.

AAC developed in CAC

IOP

CAC developed after AAC

Fig. 1B. CAC may develop even after AAC, and the acute attack may also happen even during the course of CAC. So it seems better to call these complexity of angle closures as primary angle closure or primary angle closure glaucoma depending on the presence of the optic nerve damage.

and the vagueness of classification by symptomatology, the recent suggestion for classification is to use the term ‘primary angle closure’ rather than dividing the condition into acute, intermittent, and chronic angle closure.

Mechanism

Pupillary block

The potential contact force between the pupil and lens surface increases physiologically and pathologically to create a pressure gradient between the anterior and posterior chambers, with higher pressure in the posterior. This pressure gradient makes the peripheral iris bow anteriorly and results in apposition of the iris onto

the trabecular meshwork. The extent of appositional closure determines the severity of IOP elevation and symptoms. If the appositional closure develops completely around the trabecular meshwork, the acute angle closure occurs. If the appositional closure develops partially the intermittent angle closure may occur.

Plateau iris

In some cases with specific peripheral iris configuration, the angle closure occurs without a pupillary block. The peripheral iris is shaped with an anterior bowing or plateau-like pattern. The problem is present in the peripheral iris and ciliary body. In this case, the pressure gradient between the anterior and posterior chamber is not important.

Lens-induced

In lens-induced mechanism, the problem is caused by the lens. The anterior position or the large size of the lens may increase contact with the iris and push the peripheral iris toward the trabecular meshwork. The loosening of the zonule and aging change of the lens may affect the position and the size of the lens. The inherent disproportion between the eyeball size and lens size, a larger lens compared to the size of the eyeball, can be another factor.

Precipitating factors

Although the mechanism of acute angle closure is not yet fully understood, a number of precipitating factors have been suggested. Near work, intense concentration, emotional stress, and excitement are precipitating factors that have been suggested by previous studies and reports.5-7

General illness by systemic infection may induce angle closure. Upper respiratory infection was found to be a risk factor for the attack.8 Acute angle closure has also been reported in patients with influenza, AIDS, and hemorrhagic fever with renal syndrome.

Choroidal expansion9 has been suggested as a possible mechanism of glaucoma. Along similar lines, narrowing of the anterior chamber angle and thickening of the ciliary body has been observed during the valsalva maneuver.10

Pharmacologic pupillary dilation, miotics, and drugs may precipitate acute attack. The tricyclic antidepressants with anticholinergic properties have been reported to precipitate angle closure glaucoma.11,12 Recently, an antiepileptic drug, topiramate, has been proven to induce bilateral acute angle closure associated with uveal effusion.

Symptoms and signs

Most attacks of acute angle closure are unilateral, with only 5 to 10% being bilateral.16 The symptoms of acute angle closure are related to the sudden and marked eleva-

Fig. 2. An anterior segment photograph of 58 year-old female patient with an acute angle closure attack which developed three hours before. The IOP was 54 mmHg. Conjunctival injection is observed around the limbus. In this case the injection in nasal side is more prominent. The pupil is mid-dilated due to sphincter palsy. The corneal edema was not developed due to a relatively short duration of the attack.

Fig. 3. The iris atrophy (1 to 5 o’clock position) was developed after previous acute angle closure attack.

tion of IOP. Ocular pain is caused by the expansion of ocular tissue, including the cornea, the iris, and the whole globe. A headache usually accompanies ocular pain in the form of a radiating pain.17 Nausea and vomiting are among the characteristic symptoms of acute IOP elevation. The activation of the vomiting center in the medulla may be triggered by the afferent input from the peripheral pain receptors. Vasovagal responses such as bradycardia and sweating may present. These systemic

Fig. 4. Pupillary margin may show spiral or whorl appearance (6 and 11 o’clock position) due to a sectoral sphincter damage (3 to 5 and 12 to 1 o’clock) during the acute attack.

symptoms and headache may mislead the general practitioners to refer the patients to internists or neurologists, and may delay proper treatment.11,18

The increased IOP affects the endothelial function of the cornea, which induces edema of the cornea. The corneal edema with stretched stromal lamellae causes blurred vision and halo vision around lights, with a blue-green central halo and a yellow-red peripheral halo. Corneal epithelial edema develops and causes the corneal light reflex to become irregular. The conjunctival injection starting around the limbus (ciliary injection) is related to the congestion of the ciliary body (Fig. 2). The conjuctival injection and the leakage from the conjunctival vessels result in chemosis and lid edema. Tearing is increased. The pupil is mid-dilated and fixed due to ischemic damage of the sphincter muscle. If sphincter damage is partial or sectoral, the shape of the dilated pupil may be ovoid or irregular. In severe cases, the iris vessels may also be dilated, and may be mistaken for neovascular glaucoma.

A sequel of an acute attack provides us with information regarding the characteristic features of the condition. The iris showed an atrophic change of depigmentation and thinning at the previous ischemic area of the pupil margin and iris stroma (Fig. 3). A severe attack may create a hole in the atrophic iris stroma. The papillary margin may show a spiral or whorl pattern due to irregular contraction between the areas experiencing sectoral damage (Fig. 4).

The lens showed white anterior subcapsular opacities referred to as ‘glaukomflecken’ and represented as multiple small white flecks in the pupil area, which develop as a result of ischemia of the anterior lens fibers (Fig. 5).

The focal peripheral anterior synechia and the hyperpigmentation at the area of iris contact during the attack can be observed by gonioscopy.

Fig. 5. The photograph shows the glaucomflecken on the lens surface which represents the ischemic change of the anterior lens fibers.

Diagnosis

The diagnosis of acute angle closure is based on the symptoms and signs. Confirmation of the diagnosis and differential diagnosis are done by close examination using slit-lamp biomicroscopy. The IOP is measured most accurately using a Goldmann applanation tonometer. Slit-lamp examination can reveal conjunctival injection, corneal edema, fixed dilated pupil, shallow anterior chamber, and narrow and closed angle.

In the acute stage with corneal edema, the angle is difficult to examine clearly using gonioscopy. Topical application of glycerol or 5% NaCl will make the cornea clear temporarily to allow for an examination of the angle. Opening the angle by indentation gonioscopy may differentiate appositional closure from synechial closure. Gonioscopic examination of the fellow eye provides many clues because the configuration of the chamber angle is similar between two eyes, especially when the corneal edema of the involved eye prevents angular examination.

Ultrasound biomicroscopy may aid in the evaluation of the anterior segment architecture and the mechanism of angle closure.19,20 It helps to visualize the structures posterior to the iris and provide quantitative measurements. Anterior segment optical coherence tomography was recently developed, and helps investigators to

quantitatively evaluate the angle and the anterior segments rapidly and without causing the discomfort of contacting an eyeball.21,22 The only major problem is that it cannot be used to visualize the structure posterior to the iris because the laser light does not penetrate the iris.

The fundus cannot be examined clearly due to corneal edema. Indirect ophthalmoscopy with the brightest available light may aid in the examination of the fundus and the optic disc. In a fresh and mild attack, the disc may not show any abnormal changes. In a severe and long-standing attack with congestion of the whole eyeball, the disc will show hyperemia and swelling. If an acute attack occurs during chronic or creeping angle closure, the disc may show atrophic and glaucomatous cupping due to previously accumulated damage.

The visual field examination during the attack is practically and ethically impossible. It can be assessed after the attack is relieved and the risk factors are removed. The results of field examination correlate with the optic disc findings. Field examination should be performed carefully, as it may provoke a new attack if the precipitating risks are not removed.

If the glaucomatous optic nerve head change or visual field change is observed, the diagnosis needs to be changed from acute angle closure to acute angle closure glaucoma. However, in acute angle closure, the optic nerve damage is relatively rare because the duration of IOP elevation is short unless it is missed or develops into the chronic angle closure.

Differential diagnosis of primary acute angle closure

Differential diagnosis is focused on diseases that show acute IOP elevation and similar symptoms.

Uveitic glaucoma

Even though the elevation of IOP is not always acute in glaucoma associated with uveitis, there can be an abrupt elevation of IOP with similar symptoms of acute angle closure. The associated ocular pain may be due to both IOP elevation and uveitis. Ciliary injection by uveitis may mimic acute angle closure. Differential diagnosis is made by observing the chamber reaction, keratic precipitates, and open angle, while focal PAS may be found.23,24

Glaucomatocyclitic crisis

A glaucomatocyclitic crisis, or also called Possner-Schlossman syndrome, is one of the specific types of glaucoma associated with uveitis. The elevation of IOP is typically accompanied by a recurrent episode of anterior uveitis. The chamber reaction is usually minimal, with a few keratic precipitates observed in the inferior cornea. Between attacks, the IOP is normal and there is no chamber reaction. Middle-aged men are more frequently affected than other groups. The chamber angle is wide open.25-27

Neovascular glaucoma

At the late stages of neovascular glaucoma, the angle can be totally closed by PAS because of the contraction of the fibrovascular membrane at the angle. If the angle is completely closed, the IOP may increase abruptly up to a level that may mimic AAC. Differential diagnosis is made by observing the new vessels on the surface of the iris. However, it should be kept in mind that in case of severe primary angle-closure attack, dilated iris vessels may also appear. The contraction of the fibrovascular membrane may drag the pupil margin and induce ectropion uvea with dilated pupil. At this stage, the fibrovascular membrane on the iris makes the surface of the iris appear glossy. The identification of a disease underlying neovascular glaucoma such as diabetes, central retinal vein occlusion, or ocular ischemic syndrome can aid in differentiation.28,29

Malignant glaucoma

The misdirection of aqueous fluid into the vitreous increases the posterior pressure, which in turn pushes the iris, lens, and ciliary body forward, and the angle is closed secondarily. The main differentiation is that both the central and peripheral chambers are shallow or absent in malignant glaucoma due to the pushing force from the vitreous. A detailed description of malignant glaucoma is provided in the chapter by Uranchimeg and Baasankhuu in this volume.

Lens dislocation

The anterior lens dislocation may push the peripheral iris forward to close the angle. Mostly, the patient may have a history of eyeball trauma or pathologic conditions involving the eye, including Marfan’s syndrome, homocystinuria, Weill-Marchesani syndrome, acquired syphilis, hyperlysinemia, and sulfite-oxidase deficiency. If the angle is completely closed, it will cause secondary angle closure. The identification of the lens dislocation is a key factor for diagnosis.

Steroid-induced glaucoma

Steroid-induced glaucoma may show an extreme elevation of IOP in a high responder to steroid treatment. In a high responder, the IOP level and speed are quite similar to those of AAC. The chamber is deep in the periphery.30

Treatment

Acute angle closure is considered to be an ophthalmic emergency. The key issue of treatment of acute angle closure is to relieve the acute symptoms of the patient by lowering IOP and removing the modifiable risks to prevent additional attacks.31

Medication

Medication is used to rapidly reduce IOP and remove the discomfort of the patient. If the attack is fresh (within several hours) and caused by the pupillary block mechanism, miotics can remove the pupillary block. Treatment with 1-2% pilocarpine three times every five minutes is appropriate in this case. It should not be instilled further if the pupil does not respond, because it will also aggravate the attack if the ciliary body rotates forward due to excessive instillation. For the same reason, a patient showing a very shallow anterior chamber should not be treated with pilocarpine. Aqueous suppressant, beta-blocker, carbonic anhydrase inhibitor, and alpha-2 agonist should be applied simultaneously. A hyperosmotic agent like oral glycerol or intravenous mannitol can be administered to rapidly reduce the IOP topical steroid may help to reduce symptoms and acute inflammation caused by an attack.

Laser

When the IOP is normalized or the peripheral chamber is made deep enough for laser treatment, a peripheral laser iridotomy can be performed to remove the risk of an additional attack. This procedure is described in detail in the chapter by Friedman in this volume. Before the application of the laser, the corneal edema may be transiently removed by instillation of glycerol or 5% NaCl. Recently, Argon laser peripheral iridoplasty (ALPI) was suggested as an alternative for the pretreatment of laser iridotomy. ALPI has been found to successfully reduce the IOP and deepen the peripheral chamber faster than conventional medical treatment (see the chapter by Tham et al. in this volume).

Surgery

Surgical treatment of acute angle closure is saved for rare cases in which medication and laser treatment have not had any effect. Surgical procedures include trabeculectomy, goniosynechiolysis, and phacoemulsification of the lens.

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