Ординатура / Офтальмология / Английские материалы / Clinical Pathways in Glaucoma_Zimmerman, Kooner_2001

Table 5–3. Continued

Disc hyperemia and edema early in the acute attack, the disc becomes atrophic later, with the extent of pallor often outweighing that of cupping

Nonspecific visual field constriction, which is occasionally reversible, especially in younger patients

Bradycardia

in Table 5–4, must be considered. Uveitic, neovascular, and other secondary acute glaucomas can mimic primary angle closure and lead to incorrect diagnosis and inappropriate treatment.

SUBACUTE (INTERMITTENT, PRODROMAL, OR SUBCLINICAL)

PRIMARY ANGLE-CLOSURE GLAUCOMA

Subacute angle closure is characterized by periodic and self-limited attacks of mild ocular pain and blurred vision.27 The history provided by the patient is often vague, but the examiner should listen carefully. Complaints of colored rainbows around lights, signifying corneal edema, should automatically trigger a gonioscopic examination, even if the IOP is normal and the angle seems deep upon slit-lamp examination. These rainbows differ from the monochromic halos around lights of which a patient with cataract might complain. Halos are not due to corneal edema, and therefore are not colored. Symptoms of subacute angle closure are typically greatest in the evening and usually improve by morning, presumably due to lessening of angle closure from the miosis of sleep. Because subacute angle closure can progress to acute or chronic angle closure, it is important to suspect it and perform gonioscopy on all patients giving a peculiar history of intermittent eye or brow discomfort or dull ache, blur, or transient monocular visual loss, even if the peripheral anterior chamber appears deep upon slit-lamp examination. The slit-lamp examination can mislead the examiner into assuming, incorrectly, that the angle is open. If

Table 5–4. Differential Diagnosis of Acute Primary Angle-Closure Glaucoma

Anterior uveitis

Neovascular glaucoma

Iridocorneal endothelial (ICE) syndrome

Central retinal vein occlusion

Ciliary body swelling, inflammation or cysts

Following scleral buckling or panretinal photocoagulation

Malignant (ciliary block) glaucoma/aqueous misdirection

Phacomorphic glaucoma

Subluxated lens

Phacolytic glaucoma

Nanophthalmos

Posterior segment tumors

92 Primary Angle-Closure Glaucoma

angle closure is allowed to continue undetected, progressive irreversible synechial angle closure will result. This condition often leads to a glaucomatous situation no longer manageable with laser iridectomy, but only with filtration surgery.

CHRONIC PRIMARY ANGLE-CLOSURE GLAUCOMA

Chronic angle closure has no symptoms. It develops over a long period of time, occasionally in patients with preexisting primary open-angle glaucoma. Therefore, it is essential that all glaucoma patients have initial and periodic gonioscopy, no matter how deep the peripheral anterior chamber appears at the slit lamp. When the IOP control in a patient being treated for chronic open-angle glaucoma becomes more difficult than previously, gonioscopy may reveal that chronic angle closure has begun, with varying amounts of appositional and/or synechial closure. In a predisposed, usually hyperopic, eye, as the patient ages and the crystalline lens enlarges, relative pupillary block increases, which can cause slowly progressive angle closure. This situation is occasionally discovered at the time of laser trabeculoplasty that has been scheduled for what is believed to be uncontrolled open-angle glaucoma. In such cases, laser iridectomy is necessary to relieve pupillary block and interrupt the progression of permanent synechial angle closure. Following the elimination of the underlying cause of the angle closure, medical therapy, laser trabeculoplasty, or surgical therapy are employed, as needed, for IOP lowering.

The depth of the peripheral anterior chamber as visualized at the slit lamp, although very useful in most cases for estimating the closability of the angle, can be very misleading and must not take the place of careful gonioscopy.28 Unless careful gonioscopy is periodically performed on all glaucoma patients, the assumption that an angle, based on the slit-lamp examination, is open and not closable can lull the ophthalmologist into a dangerously false sense of security. In the early stages of chronic angle-closure glaucoma, permanent synechial angle closure can progress despite normal IOP, especially if aqueous suppressant therapy, such as carbonic anhydrase inhibitors or topical beta-blockers, are used. Eventually, a critical fraction of the circumference of the trabecular meshwork becomes permanently closed with synechias. At this point, the remaining fraction of the angle that is still open provides insufficient facility of outflow to keep pace with aqueous production, and the IOP rises. In many such cases, following relief of pupillary block with iridectomy, the pressure remains high despite medications and laser trabeculoplasty, and filtration surgery is required. In chronic primary angle-closure glaucoma, even if glaucoma medications successfully lower the IOP, laser iridectomy is necessary to preserve that portion of the angle not yet closed with peripheral anterior synechias. It is very difficult to predict in which cases of primary angle closure the IOP will be controlled with iridectomy alone, and which cases will require filtration surgery. Because laser iridectomy is relatively safe compared to filtration surgery, it should be performed, if possible, in all cases. Then if the IOP remains unacceptably high,

despite the maximum benefit from glaucoma medications and laser trabeculoplasty to the remaining open angle, surgery can be performed.

Treatment and Management

How Is Primary Angle Closure Treated?

The first goal in the management of primary angle closure is to eliminate relative pupillary block with an iridectomy. The initial evaluation of primary angle closure and its management is depicted in Figure 5–4, culminating in laser iridectomy. In the case of acute angle closure, the cornea is often too edematous to permit laser. One must first break the attack medically to allow the cornea to clear. Acute angle closure is an emergency and must be resolved quickly to protect the optic nerve from pressure-induced damage and to prevent permanent synechial angle closure. Then, once iridectomy has eliminated relative pupillary block, the patient must be carefully reevaluated for the important, but often neglected, management necessary after iridectomy, which is diagrammed in Figure 5–5.

How Is an Attack

of Acute Primary Angle Closure Treated?

MEDICAL THERAPY

Drugs that are useful in the treatment of acute angle closure glaucoma are listed in Table 5–5.

Hyperosmotic Drugs Hyperosmotics are the cornerstone of medical therapy for acute angle-closure glaucoma. Because they lower the IOP by shrinking the volume of the vitreous, hyperosmotics work independently of neuromuscular action of the iris and of the production of aqueous. Until iris muscular paralysis due to pressure-induced ischemia is relieved by the lowering of IOP provided by hyperosmotic drugs, pilocarpine, a direct parasympathomimetic, cannot stimulate the pupillary sphincter to cause needed miosis. Also, since the production of aqueous humor is significantly depressed by the acute pressure elevation, aqueous suppressants such as beta-blockers and carbonic anhydrase inhibitors, although helpful, cannot by themselves break an acute attack.

If at all possible, the patient should have nothing to eat or drink prior to the administration of hyperosmotics and for 2 hours afterward. Ice chips can be given for thirst, if necessary. In addition, oral hypersomotics commonly cause nausea and occasional vomiting in the already ill patient. This can interfere with their administration and retention. Injectable antiemetic medication can be useful in this situation. The patient should be observed closely and not discharged from the office immediately after hyperosmotics. Possible side effects are headache, confusion, cardiac arrhythmia, and subdural or subarachnoid hemorrhage.

IOP, intraocular pressure

Figure 5–5. Decision tree: strategy for therapy of primary angle-closure glaucoma after iridectomy has eliminated relative pupillary block.

Other Medications

Miotics29,30,31,32, beta-blockers, carbonic anhydrase inhibitors, and alpha agonists are described in Table 5-5.

THERAPEUTIC CORNEAL INDENTATION

Indentation of the anesthetized central cornea with a sterile cotton-tipped applicator, indentation goniolens (Zeiss, Posner, or Sussman), or applanation

96 Primary Angle-Closure Glaucoma

Table 5–5. Medical Therapy for Acute Angle-Closure Glaucoma

A.Hyperosmotics

1.Oral hyperosmotics

a.Isosorbide (Ismotic) 45%

Contributes to the tonicity of the blood and is excreted unchanged in the urine; therefore, no caloric problem for diabetics

Other side effects are less than with glycerin

Dosage = 1.5 g/kg 1.5 mL/lb 3 mL/kg (therefore, one 220-mL bottle for a 70-kg/154-lb adult)

b.Glycerin (Osmoglyn) 50%

Metabolized before excretion (calories for diabetics)

Dosage = 2–3 mL/kg or 140–210 mL for a 70-kg/154-lb adult

2.Intravenous hyperosmotics Mannitol 20–25%

Dosage = 1-2 g/kg (e.g., a 50–100 cc bolus of 20–25% solution intravenously, over 20 minutes for a typical adult)

This bolus is as effective as a slow drip of greater volume of lower concentration of mannitol solution

B.Miotics

1.Pilocarpine 2% every 30 minutes in the affected eye (2% solution is as effective as higher concentrations with less risk of cholinergic toxicity from repeated administration); because pilocarpine is a direct parasympathomimetic, it does not influence the iris sphincter musculature until hyperosmotic drugs and/or therapeutic corneal indentation have lowered the intraocular pressure (IOP), which, in turn, relieves the iris ischemia

2.Thymoxamine31,32 (not available in the U.S.) and dapiprazole29,30 (Rev-Eyes) are α-adrenergic blockers that produce miosis by relaxing the iris dilator muscle (this is a theoretical advantage over pilocarpine, which stimulates the iris sphincter and ciliary muscle and moves the lens/iris diaphragm forward, further shallowing the anterior chamber)

3.Strong miotics: indirect parasympathomimetics (phospholine iodide, Humorsol) are contraindicated for primary angle closure because they produce iris congestion, can worsen pupillary block, and can enhance formation of peripheral anterior synechiae

C.Topical beta blockers

Be careful of systemic side effects and overdosage; use lacrimal occlusion and do not exceed the maximum recommended 12-hour frequency of administration

Cosopt, a combination of timolol and dorzolamide in a single drop, simplifies therapy if both beta-blockers and topical carbonic anhydrase inhibitors are desired simultaneously

D.Carbonic anhydrase inhibitors (CAIs)

1.Topical CAIs

Dorzolamide 2% (Trusopt) alone or in combination with timolol maleate in Cosopt

Brinzolamide 1% (Azopt)

2.Oral and Parenteral CAIs

Acetazolamide (Diamox or AK-Zol) 250–500 mg orally (intramuscular or intravenous, if the patient is nauseated)

Methazolamide (Neptazane) 25–100 mg orally

E.Alpha agonists

1.Apraclonidine 0.5% or 1% (Iopidine)

2.Brimonidine 0.2% (Alphagan)

prism (on 20 seconds, off 10, on 20, etc.) can be invaluable in breaking an acute attack of primary angle-closure glaucoma.33 Therapeutic corneal indentation works by the same principle as diagnostic indentation gonioscopy. The pressure applied to the central cornea pushes aqueous from the central anterior chamber into the peripheral anterior chamber, which opens the angle and allows aqueous to reach the trabecular meshwork. A variation on this theme was described by Kimbrough et al,34 who reported the successful relief of acute angle closure with adjunctive retrobulbar anesthesia followed by intermittent application of the “super pinkie” ocular compression device.

PAIN, NAUSEA, AND VOMITING

Medical therapy should be provided.

LASER PERIPHERAL IRIS GONIOPLASTY

Argon laser photocoagulation can be used to shrink and flatten the peripheral iris to open the angle in attacks of acute angle-closure glaucoma that fail to respond to medications and corneal indentation.35,36 Often, the cornea is not sufficiently transparent to perform definitive laser iridectomy, but is clear enough to permit the application of laser energy to shrink the peripheral iris. In this situation, gonioplasty can be employed to open some or all of the angle to lower the IOP and clear the cornea, making subsequent laser iridectomy possible. The effect of gonioplasty is often transient and therefore is not a substitute for definitive relief of relative pupillary block with iridectomy. Similarly, attempted argon laser iridectomy, even in the absence of patency, can inadvertently “peak” the pupil in the meridian toward the laser iridectomy site, transiently relieving relative pupillary block, and breaking the acute angle-closure attack. For this reason, care must be taken to be certain that the iridectomy is patent. If it is not, the iridectomy must be completed because the transient pupilloplasty effect will usually lessen with time and eventually predispose the eye to recurrence of angle closure. In addition to its value in treating an acute attack of angle closure, argon laser gonioplasty has several other valuable uses in the management of primary angle closure as listed in Table 5–6.

What Should Be Done If the Acute Attack of Angle Closure Is Unresponsive to Medical Therapy and Laser Gonioplasty, and the Cornea Is Not Sufficiently Clear to Allow Laser Iridectomy?

In this situation, surgical iridectomy is required. The question is, Will iridectomy alone resolve the problem or should a filtration operation be performed? Before the availability of laser iridectomy, this was a common dilemma for the ophthalmologist confronted with acute angle closure. It is unpleasant for both the patient and the surgeon to have to follow one intraocular surgical pro-

98 Primary Angle-Closure Glaucoma

Table 5–6. Argon Laser Gonioplasty: Indications

Indications

During an acute attack of primary angle-closure glaucoma, when the cornea is not sufficiently clear to allow laser iridectomy, gonioplasty can occasionally be used to open segments of the angle to help lower the pressure and clear the cornea permit definitive treatment (laser iridectomy)

Following laser iridectomy for acute angle-closure glaucoma, gonioplasty can be used to break fresh peripheral anterior synechiae to open the angle

Following laser iridectomy, when appositional angle closure/closability persists in the form of plateau iris syndrome, gonioplasty can be used to remove the peripheral iris roll from the vicinity of the trabecular meshwork; retreatment is often necessary; the patient should be followed with periodic gonioscopy indefinitely

Gonioplasty can be used to preserve open angle in concert with laser iridectomy in nanophthalmic eyes; these laser options are especially important because intraocular surgery in nanophthalmos is fraught with danger

Gonioplasty laser settings

Use the lowest settings needed to achieve a moderate stromal burn and shrinkage of tissue and the desired anatomic result

Use of three-mirror lens is optional but preferred

Treat less than the entire circumference of available angle in eyes where inflammation and debris might cause a dangerous pressure spike and damage a cupped and vulnerable optic nerve

cedure with another. When surgical peripheral iridectomy becomes necessary, operative anterior chamber deepening and gonioscopy allows quantification of permanent synechial angle closure in the operating room, where the decision between iridectomy and filtration surgery can be weighed.37,38 Also, at that time, operative goniosynechialysis can be used to break fresh peripheral anterior synechias to restore angle anatomy and aqueous outflow.21,22 Although operative goniosynechialysis has been successfully employed up to 1 year following acute angle closure, the earlier one can open and restore the functional anatomy of the angle, the better. Depending on how much of the angle is not yet closed with synechias, a decision must be made whether to perform iridectomy alone or as part of a filtration operation. Chandler and Simmons37 have recommended filtration surgery if more than 6 clock hours of angle are closed with synechias; surgical peripheral iridectomy alone if 4 or less clock hours are closed; and that the surgeon use his own judgment for eyes with 4 to 6 clock hours of synechial angle closure. These recommendations, although very helpful, are not foolproof. Mixed mechanism glaucoma may be present with very poor facility of outflow and high pressure, even with an entirely open angle. If, following surgical iridectomy, the IOP remains uncontrolled; glaucoma medications, laser trabeculoplasty, and glaucoma filtration surgery must be employed, as needed, to control any residual glaucoma at an acceptable level of IOP.

What Should Be Done After Breaking the Attack

of Acute Angle Closure?

When the acute attack is broken or the cornea is sufficiently clear, proceed with laser iridectomy to eliminate pupillary block and prevent its recurrence and angle closure.39–41 Remember that after iridectomy, there is yet much work to do, even if the pressure has improved. Figure 5–5 diagrams the important, but often neglected, management of primary angle closure following iridectomy.

What Are Some Useful Guidelines for Laser Iridectomy Technique?

PRETREATMENT

1.If the pupil is not already miotic from medications used to break an acute attack, constrict the pupil for a taut iris and easy penetration, for example, with pilocarpine 2 to 4% every 5 minutes for three doses until the pupil is nonreactive.

2.An alpha agonist such as brimonidine 0.2% (Alphagan) or apraclonidine 0.5 or 1.0% (Iopidine), and/or other glaucoma medications are helpful in minimizing the risk of a postlaser pressure spike.42

TECHNIQUE

1.The Abraham or Wise iridectomy lenses greatly facilitate iris penetration.

2.Argon laser: Iridectomy with the argon laser is an art form.43–47 Unlike the

neodymium:yttrium-aluminum-garnet (Nd:YAG) photodisruptive iridectomy, this photocoagulative technique must be varied depending on differences in iris color and its relative tendencies to absorb or reflect laser energy. For example, “chipping away” with many high power/short exposure burns is very effective for dark brown irises. On the other hand, the “gas bubble” technique described by Hoskins and Migliazzo46 is wonderful for light blue irises. For iris coloration in between these two extremes, a variety of techniques can be used such as the Simmons-Deppermann “drumhead” technique.47 These methods are listed in Table 5–7; however, numerous techniques have been used successfully. This list may serve as a starting point from which surgeons can refine their own techniques.

3.Nd:YAG laser: The action of Nd:YAG photodisruptors, unlike argon laser photocoagulators, is independent of the propensity of the iris to absorb or reflect laser energy.48,49 With the Nd:YAG laser, the same iridectomy technique can be used regardless of iris color. However, thin, light blue irises are more easily penetrated with Nd:YAG laser than thick, dark brown ones.

4.Site of iridectomy:

•Base of iris crypt or thin spot

•Iris freckle, if argon laser used

•Avoid visible blood vessels, especially with Nd:YAG