Albert & Jakobiec's Principles & Practice of Ophthalmology, 3rd Edition

CHAPTER 219 - Laser and Surgery Treatment of Angle-Closure Glaucoma

M. Roy Wilson,
Mark Gallardo

Obstruction of the flow of aqueous humor from the posterior chamber to the anterior chamber occurs during a relative or absolute pupillary blockade. This interference of the normal physiologic pathway for aqueous flow induces a pathologic pressure gradient between the posterior and anterior chambers. This results in anterior billowing of the peripheral iris and the trabecular meshwork is obstructed. Creating a full thickness hole in the peripheral iris provides an alternate pathway for aqueous to flow; pressure between the two chambers is normalized and the force that pushes the iris forward is eliminated.

The mechanism for creating this alternate pathway has evolved over the past several decades from conventional to laser surgery. The concept of surgical iridectomies for the treatment of acute glaucoma was introduced in 1857 by von Graefe,[1] but his concept did not gain acceptance until Curran uncovered and explained the mechanisms involved in relative pupillary-block glaucoma in 1920.[2] Barkan soon after introduced an anatomic classification of the causes of glaucoma, and surgical peripheral iridectomy became established as the treatment of choice for primary angle-closure glaucoma.[3]

Since the 1980s, the use of lasers has almost eliminated the need to perform surgical peripheral iridectomies. Laser facilitated iridotomies have undergone an evolution since the birth of the laser in the mid-twentieth century. Use of a light source to create a full-thickness hole in the iris was first introduced in 1956 by Meyer-Schwickerath.[4] These investigators used an arc xenon light to create their iridotomy, but the frequently encountered corneal and lens opacities hindered it's widespread use. The development of the argon laser in the late 1970s revolutionized the technique for creating a peripheral iridotomy because it provided more energy in a shorter period of time and eliminated some of the complications seen with other light sources.[5-14] Currently, peripheral iridotomies are most commonly created with the neodymium:yttrium-aluminum garnet (Nd:YAG) laser alone or combined with the argon laser. Other coherent light sources such as the Q-switched ruby laser, krypton laser, and the organic dye laser have proven capable of safely creating an iridotomy, but have had limited utility due to their lack of availability.[15-18]

This chapter reviews the indications, techniques, and complication profiles for both laser iridotomies and surgical iridectomies. It also reviews other techniques such as laser gonioplasty, sector iridectomy, and goniosynechialysis which are useful adjuncts in the management of complicated cases of angle-closure glaucoma.

INDICATIONS

There are a number of conditions that may require the creation of an alternate or adjunctive pathway for aqueous to flow. In most cases, the nonincisional laser iridotomy is the preferred modality due to its proven efficacy, relative convenience and ease. Conditions do, however, exist which may preclude the creation of a laser iridotomy or interfere with its patency. These include: (1) lack of functioning laser equipment, (2) uncooperative patient in which eye or head movement may be hazardous, (3) anterior uveitis and rubeosis which may lead to excessive inflammation, (4) poor visualization of iris due to corneal edema or opacification, or (5) presence of shallow or flat anterior chamber with broad cornea-iris contact. A surgical peripheral iridectomy is also indicated when iris tissue is necessary for pathologic analysis or when created as an adjunct to glaucoma filtering or cataract surgery.

Key Features: Indications for Iridotomy/Iridectomy

  

.   

Angle-closure glaucoma

  

.   

Primary pupillary block - acute, subacute, chronic

  

.   

Aphakic

  

.   

Pseudophakic

  

.   

Seclusio pupillae

  

.   

Occludable narrow anatomic angles

  

.   

Hyperopia

  

.   

Nanophthalmic

  

.   

Plateau iris configuration

  

.   

Phacomorphic crowding of the angle

  

.   

Combined-mechanism glaucoma

  

.   

Malignant glaucoma

 

 

LASER IRIDOTOMIES

PREOPERATIVE PREPARATION

Application of laser energy to the structures of the anterior segment may induce postoperative intraocular pressure (IOP) spikes.[19-21] To avoid this pressure increase, patients can be given IOP lowering agents prior to laser treatment. The alpha-adrenergic agonists apraclonidine and brimonidine have proven effective in blunting or even preventing such an event.[22-26] Other classes of medications such as prostaglandin analogues, beta-blockers, and carbonic anhydrase inhibitors have been evaluated and have also been shown to be effective at preventing or reducing IOP spikes.[27-29] It is common to use apraclonidine 0.5% and instill the medication 30 min prior to laser treatment.

Pre-treatment with a miotic agent such as 1-2% pilocarpine is also important. Miosis places the iris on stretch and thins the peripheral iris which allows for easier perforation. The miotic agent should be instilled three times every 5 min beginning 30 min prior to the laser treatment. Patients should be informed that the miotic may induce a mild brow ache.

Anesthesia is usually limited to that of a topical anesthetic agent such as tetracaine hydrochloride 0.5% or proparacaine hydrochloride 0.5%. While the anesthetic is very effective in eliminating the patients' awareness of the iridotomy lens on the corneal surface, it does not anesthetize the iris. Some patients complain of a 'pin-prick' sensation with each laser shot, but this is usually tolerated. In rare circumstances, patients may require a retrobulbar or peribulbar anesthetic injection.

In cases of acute angle closure or other conditions causing corneal edema, visualization of the iris may be difficult. In such situations, it may be necessary to treat the cornea with topical glycerin to dehydrate the cornea and maximize clarity.

 

 

SELECTION OF LASER

There are a variety of techniques to perform an iridotomy using a myriad of laser sources. The Nd:YAG laser has become the principle laser for most surgeons (Fig. 219.1), although the diode and argon lasers are also commonly used. In addition, some surgeons prefer using the lasers sequentially; the coagulative argon laser to first thin the iris and coagulate iris vessels and then the photodisruptive Nd:YAG laser to complete the iridotomy (Fig. 219.2). This combined technique is valuable in patients with the following conditions: (1) patients with thick, dark irides, (2) those on anticoagulants or who suffer from other bleeding diathesis, and (3) those with friable iris vessels as in uveitis and iris neovascularization (See Table 219.1 for laser settings).

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FIGURE 219.1  The laser energy is passed through the iridotomy lens and focused onto the iris. With successive shots, the iris is excavated and thinned. Once the stroma is cleared, the iris epithelium will be encountered and perforated providing a path for aqueous to flow from the posterior chamber into the anterior chamber.

 

 

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FIGURE 219.2  Illustration showing combined technique: The coagulative argon or diode laser is used to focally thin the iris and coagulate iris vessels (left). The Nd:YAG laser is then used to perforate the iris and complete the iridotomy (right).

 

 


TABLE 219.1   -- Settings for Laser Iridotomy

  

 

Nd:YAG

  

 

-Energy: 4-6 mJ

  

 

-Applications: 1-10 bursts using 1-3 bursts per second

  

 

Argon Green (long pulse for light-colored eyes)

  

 

-Power: 700-1500 mW

  

 

-Spot size: 50 ?m

  

 

-Time: 0.2 s

  

 

-Applications: 1-30

  

 

Argon Green (short pulse for dark-colored eyes)

  

 

-Power: 1000-1500 mW

  

 

-Spot size: 50 ?m

  

 

-Time: 0.05-0.2 s

  

 

-Applications: 50-100

  

 

Diode

  

 

-Power: 750-1250

  

 

-Spot size: 50-75 ?m

  

 

-Time: 0.05-0.1 s

  

 

-Applications: 20-50

  

 

Combined Argon/Diode and Nd:YAG

  

 

Argon/Diode - pre-treatment

  

 

-Power: 1000 mW

  

 

-Spot size: 50 ?m

  

 

-Time: 0.02-0.05 s

  

 

-Applications: 5-25

  

 

Nd:YAG - iris perforation

  

 

-Energy: 4-6 mJ

  

 

-Applications: 1-10 bursts using 1-3 pulses per burst

 

Each laser has its own set of benefits and drawbacks. The Nd:YAG is able to exert its effect on the iris independent of the amount of iris pigmentation. It is equally efficacious in light and dark irides. On the other hand, the energy from the argon and diode, is dependent on iris pigmentation; more the pigment, greater is the effect. Although both types can create patent iridotomies, late closure is found more commonly with the argon than with the Nd:YAG.[30]

 

 

TECHNIQUE

The patient is positioned comfortably and instructed to avoid excessive head movement. Using the slit beam, the relationship of the superior lid margin to the corneal limbus is evaluated to determine the optimum site of treatment. The site selected should allow full coverage of the iridotomy by the lid margin to avoid postoperative visual disturbances.[31] An iridotomy lens is placed on the cornea using a coupling agent such as methylcellulose. The two most widely used iridotomy lenses are the Abraham and Wise lenses. These lenses are modified Goldman fundus lenses with a planoconvex button attached to their anterior surfaces with powers of +66.0 diopters and +103 diopters, respectively. These high-powered buttons magnify the underlying iris and provide better visualization of the iris detail (Fig. 219.3). The optical properties of the magnifying lenses also increase the effective laser power in the area being treated.[32]

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FIGURE 219.3  Image of the iris viewed through a slit lamp without (left) and with (right) an iridotomy lens. Note magnified iris detail.
Compliments of Paul Comeau, CRA, University of Texas Health Science Center-San Antonio.

 

 

An iris crypt is localized in the predetermined area of treatment between 11 and 1 o'clock position. (Fig. 219.4) When using the argon laser, the 12:00 position should be avoided as gas bubbles may form and hinder the view of the treatment area. The laser is focused through the lens button onto the iris crypt. In the case of the Nd:YAG laser, a helium-neon aiming beam is associated with the Nd:YAG laser, the laser energy is focused slightly anterior to the focus of the aiming beam. As the laser energy increases, the laser focus moves even further anteriorly. Because the aiming beam and the laser energy are not precisely coupled, it may be necessary to place the focus point of the aiming beam slightly posterior to the surface of the iris. To minimize the possibility of causing retinal foveal lesions, the laser beam should be directed away from the posterior pole.[33]

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FIGURE 219.4  Photo illustrating recommended locations of iridotomy placement. Straight line represents location of upper eyelid margin.

 

 

After the aiming beam is focused on its desired location, the laser energy is applied and the effect it has on the iris is evaluated to determine if more or less energy is needed. Once the energy is appropriately titrated, treatment is resumed with sequential applications of laser shots onto the iris. As the iris becomes excavated, the aiming beam will need to be re-focused further posteriorly. When the laser energy is absorbed by the iris, pigment may be liberated obscuring the view of the iridotomy site. This tends to occur more commonly with the Nd:YAG laser. When this occurs, the procedure should be temporarily halted to allow the plume of pigment to resolve.

Following clearance of the iris stroma, the iris epithelium is perforated and a gush of fluid will be seen flowing through the iridotomy from the posterior chamber into the anterior chamber. In the setting of pupillary-block glaucoma, successful creation of the iridotomy may be accompanied by a widening of the angle and deepening of the anterior chamber. (Figs 219.5 and 219.6) When using the argon or diode lasers, iris stromal contraction may pull the pupil toward the iridotomy treatment area and break the pupillary block. In such cases, even if the iris has not been perforated, aqueous will flow through the pupil and may deepen the chamber.

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FIGURE 219.5  Gonioscopic view of chamber angles pre (top) and post (bottom) peripheral iridotomy in a patient with angle-closure glaucoma. Note the deepening of the angle and visibility of angle structures after the iridotomy was performed.
Courtesy of Robert Ritch, MD, New York Eye and Ear Infirmary.

 

 

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FIGURE 219.6  Ultrasound biomicroscopy showing angle configuration in a patient with angle-closure glaucoma before (left) iridotomy and after (right) iridotomy. Arrows point to area of trabecular meshwork.
Courtesy of Robert Ritch, MD, New York Eye and Ear Infirmary.

 

 

When using the combined technique, the argon is applied to create a peripheral crater to thin the iris to approximately one-fourth of its original thickness and to coagulate underlying vessels. The patient is then transferred to the Nd:YAG laser to complete the iridotomy. Combining the two laser techniques reduces the amount of energy required than when the argon is used alone.[34] Pre-treatment with argon laser also decreases the incidence of microhyphema seen when the Nd:YAG laser is used alone.[35]

 

 

POSTOPERATIVE MANAGEMENT

After creating the iridotomy, an additional drop of apraclonidine 0.5% is instilled into the treated eye. Gonioscopy should be performed to determine if the angle is still occludable or if synechial closure is present. The IOP should be checked immediately after the laser and again 1 h after the procedure is performed to determine if additional ocular hypotensive agents may be necessary. If the IOP is stable, the patient may be discharged and instructed to use prednisolone acetate 1% four times per day in the treated eye. At the 1-week follow-up examination, the IOP, anterior chamber reaction, patency of the iridotomy, and lens clarity should be assessed. Gonioscopy should also be performed to evaluate the peripheral iris configuration and possible need for additional therapy, such as laser iridoplasty. It is also recommended to perform a dilated fundus examination at this visit. In conditions where delayed iridotomy closure may occur, as in uveitis or rubeosis, additional follow-up several weeks later is indicated.

 

 

COMPLICATIONS

Key Features: Complications of Laser Iridotomy

  

.   

Increased intraocular pressure

  

.   

Corneal burns/edema

  

.   

Transient iritis

  

.   

Hyphema/microhyphema

  

.   

Pupillary distortion

  

.   

Closure of iridotomy

  

.   

Posterior synechiae

  

.   

Cataract formation

  

.   

Retinal detachment

  

.   

Retinal burns

  

.   

Cystoid macular edema

  

.   

Choroidal effusion

  

.   

Aqueous misdirection

The two most common complications associated with laser iridotomies are closure of the iridotomy and IOP spike. To reduce the incidence of closure, the iridotomy should be at least 150 micrometers in size. The IOP spike can occur immediately following the procedure, but usually occurs within the first 24 h. As previously mentioned, this can be avoided or blunted by instilling an IOP-lowering agent preoperatively and postoperatively. Other rare complications include corneal endothelial damage with focal corneal edema, anterior capsule disruption with secondary lens opacification, hyphema, aqueous misdirection, choroidal effusion, retinal burns, retinal detachments, cystoid macular edema, and monocular diplopia.[36-43]

 

 

LASER GONIOPLASTY

Key Features: Indications for Argon Laser Gonioplasty/Iridoplasty

  

.   

Plateau iris configuration/syndrome

  

.   

Narrow anatomic angles

  

.   

Phacomorphic narrowing of angles (intumescence, microspherophakia)

  

.   

Nanophthalmos

  

.   

Hyperopia

  

.   

Following scleral buckle

  

.   

Angle-closure glaucoma

  

.   

Post-iridotomy with persistent narrow angles

  

.   

Pre-iridotomy when corneal edema prevents iridotomy creation

  

.   

Goniosynechialysis post-treatment

  

.   

Open-angle glaucoma

  

.   

Adjunct to laser trabeculoplasty

 

Key Features: Complications of Argon Laser Gonioplasty/Iridoplasty

  

.   

Increased intraocular pressure

  

.   

Transient iritis

  

.   

Peripheral anterior synechiae

  

.   

Pupillary distortion

  

.   

Iris atrophy

  

.   

Iris perforation (inadvertent iridotomy)

First described by Krasnov in 1974, laser gonioplasty or iridoplasty is a procedure designed to flatten out the peripheral iris. Application of broad, long-duration thermal burns to the peripheral iris causes contracture of the iris and widens the angle between the iris and cornea.(Fig. 219.7) It is used alone or as an adjunct to treat a variety of disorders associated with narrow anatomic angles.[44-47]

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FIGURE 219.7  Ultrasound biomicroscopy of a patient with plateau iris configuration. Note shallow angle (arrow) between the peripheral iris and cornea before iridotomy (left) and after iridotomy (right).
Courtesy of Robert Ritch, MD, New York Eye and Ear Infirmary.

 

 

There are two ways to focus and apply the thermal energy to induce contracture of the peripheral iris. The iris can be treated directly with or without a contact lens (iridoplasty), or indirectly using a mirrored lens (gonioplasty) (Fig. 219.8). The Abraham lens may be used for iridoplasty and the three-mirrored Goldman lens may be used for gonioplasty. The eye is pre-medicated in a manner similar to a laser iridotomy using an IOP-lowering agent, miotic agent, and topical anesthetic.

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FIGURE 219.8  Figure on left depicts iridoplasty where laser energy is focused directly onto iris without aid of focusing lens. Figure on right depicts gonioplasty where energy is focused through a mirrored lens (Goldman) onto iris of opposite quadrant.

 

 

After positioning the patient at the laser, the laser beam should be directed at the peripheral iris just inside the iris root. For conditions with narrow anatomic angles requiring 360° of treatment, laser spots should be placed one to one-and-a-half spots sizes apart. (Fig. 219.9) If anterior synechiae is present, the laser should be applied central to the synechiae and applied more peripherally with each consecutive shot (See Table 219.2 for laser settings).

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FIGURE 219.9  Photo of a patient following iridoplasty. Areas of treatment appear darker than neighboring iris (arrows). Note distance between treated areas.
Courtesy of Robert Ritch, MD, New York Eye and Ear Infirmary.

 

 


TABLE 219.2   -- Settings for Argon Laser Gonioplasty/Iridoplasty

-Power: 100-300 mW

-Size: 200-250 ?m

-Time: 0.2 s

-Spacing: 1-1.5 spot sizes apart

 

Note:When using the Abraham lens, the laser power will be condensed into a small area and less power or a larger spot size may be needed.

 

 

As with the iridotomy, the energy should be titrated to ensure an adequate thermal effect while avoiding excessive tissue charring. The desired effect will be that of tissue contracture without pigment liberation or iris stromal penetration. When performing gonioplasty, the iridocorneal angle can be directly visualized. When performed correctly, deeper angle structures should become visible as the iris contracts.

Following treatment, the patient is managed with a topical steroid. As complications are minimal and typically limited to peripheral anterior synechiae and mild anterior chamber inflammation, follow-up examination can be performed 1 week following laser treatment. Gonioscopy should be performed to reassess the iridocorneal angle and IOP should be checked as spikes may occur.

 

 

SURGICAL IRIDECTOMIES

PREOPERATIVE PREPARATION

Local anesthesia with lidocaine 2%, injected in the retrobulbar or peribulbar space, combined with a lid block is desirable. General anesthesia should be reserved for uncooperative patients. In order to reduce the risk of postoperative endophthalmitis, the eye and ocular adnexa should be treated with a betadine 5% solution. Pre-treatment with topical antibiotics may also be added.

 

 

MIOSIS

Pupillary constriction facilitates the creation of a surgical iridectomy by placing the iris on stretch. Miosis can be achieved preoperatively by instilling 2-4% pilocarpine solution topically every 30 min for three doses or intraoperatively with an intracameral injection of acetylcholine.

 

 

SURGICAL TECHNIQUE

Exposure of the superior limbus is achieved by placing a superior rectus bridal suture using a 4-0 silk suture. A paracentesis is made though clear cornea at the 10 or 2 o'clock position with a Wheeler knife or simply a sharp blade. The corneal incision is made in one of the superior quadrants just anterior to the limbal corneal vessels. This incision should be perpendicular to the surface, ?3 mm wide, and extend through two-thirds of the corneal thickness. In the limbal approach, a small fornix-based conjunctival flap is made in one of the superior quadrants, and the incision is placed ?1-1.5 mm behind the corneoscleral junction. This incision should also be ?3 mm wide and two-thirds deep but may be beveled slightly anteriorly.

A suture of 10-0 nylon is pre-placed through the groove and looped out of the wound (Fig. 219.10a). While the assistant spreads apart the lips of the groove by grasping the two parts of the suture with tying forceps, Descemet's membrane is penetrated with a sharp blade, and the anterior chamber is entered (Fig. 219.10b). Care is taken to ensure that the internal opening is nearly as wide as the external incision (Fig. 219.10c).

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FIGURE 219.10  (a) Pre-placement of 10-0 nylon suture. (b) Incision into the anterior chamber with a sharp blade. (c) An internal incision is made to be as wide as the external incision. (d) The prolapsed iris is grasped and cut. (e) Massaging the peripheral cornea with a blunt instrument. (f) A picture of the successful iridectomy. (g) The pre-placed suture is tied, and the knot is buried.

 

 

The assistant may facilitate prolapse of the iris by pulling on the pre-placed suture and exerting gentle pressure on the posterior lip of the incision. Once the iris has prolapsed, it is grasped with fine forceps and cut using Vannas or deWecker scissors (Fig. 219.10d). If the iris does not prolapse, the anterior chamber must be entered with fine nontoothed forceps and the iris must be grasped and gently lifted out of the incision for surgical excision. The excised tissue should be inspected for the presence of the pigment epithelium.

Repositioning of the iris is usually achieved by gentle massage over the peripheral cornea radially with a blunt cannula or muscle hook (Fig. 219.10e). Irrigation with acetylcholine through the previously made paracentesis may facilitate this process. Occasionally, it may be necessary to gently push the iris tissue back into the anterior chamber with an iris spatula. Care must be taken to avoid inserting instruments into the anterior chamber through the incision site because this may inadvertently damage the lens. After successful repositioning of the iris, the iridectomy should be visible and the pupil should be round and centrally located (Fig. 219.10f). If necessary, the anterior chamber can be re-formed with balanced salt solution through the paracentesis site.

The pre-placed suture is then tightened and tied to re-approximate the wound (Fig. 219.10 g). The suture is cut close to the knot, and the knot buried. If the limbal approach is used, the conjunctiva is brought over the wound and is closed with a 7-0 Vicryl suture. Subconjunctival antibiotics and corticosteroids are injected inferiorly.

 

 

POSTOPERATIVE MANAGEMENT

As is with all intraocular surgery, the patient should be examined by slit-lamp biomicroscopy the day following surgery. In addition to visual acuity and IOP, the integrity of the corneal wound, the anterior chamber depth and its level of inflammation, and the patency of the iridectomy are assessed. Topical antibiotics are administered four times per day. A topical steroid is also prescribed and it's dosing and eventual tapering is dependent on the degree of inflammation. A cycloplegic agent such as tropicamide hydrochloride 1% or cyclopentolate hydrochloride 1% may be administered twice-daily if the eye is inflamed to minimize the chances of posterior synechiae formation. The surgeon should be aware of the possible IOP rise that can occur as a response to steroids or possibly from mydriatic-induced angle crowding by the peripheral iris. If the ophthalmic exam is stable on the first postoperative day, the patient should be re-evaluated seven to 10 days later. Gonioscopy should be performed at this time to evaluate the effect of the procedure.

 

 

COMMON COMPLICATIONS

Intraoperative

Key Features: Surgical Iridectomy - Intraoperative Complications

  

.   

Intraocular hemorrhage

  

.   

Anterior capsular disruption of the crystalline lens

Serious complications are rare during the creation of a surgical iridectomy, but intraocular hemorrhage, peripheral anterior synechiae, and disruption of the lens capsule have been reported.[48-52] While constructing the corneal or limbal wound, care must be taken to avoid penetrating the lens capsule with the surgical blade, and causing cataract formation. Placement of the wound is important because creation of a wound that is too posterior may lead to inadvertent penetration of the posterior segment and cause vitreous to be expelled from the eye.

Rapid depressurization of an eye with high IOP, as in acute angle closure, can lead to the development of a suprachoroidal hemorrhage. The risk of suprachoroidal hemorrhage can be lessened by aggressively reducing the IOP with topical and systemic aqueous suppressants augmented with systemic hyperosmotic agents preoperatively.

Bleeding can occur from both the iris and ciliary body while excising the peripheral iris. This is usually a self-limited condition. In cases of excessive bleeding, hemostasis may be achieved by thermocautery using Simmons-Savage diathermy or similar instrument, inducing vasoconstriction with topical epinephrine 1:1000, or injection of an air bubble or a viscoelastic agent to tamponade the bleeding vessels. When a viscoelastic agent is injected into the anterior chamber, care must be taken to remove the viscoelastic once bleeding is controlled to avoid postoperative pressure elevation.

Postoperative

Wound leak

As with other incisional ophthalmic surgeries, wound leaks can occur. Proper wound closure with a 10-0 nylon suture can help avoid this complication and its sequelae. Excessive leakage can lead to anterior chamber flattening, hypotony, and choroidal effusion. Leaks can be treated with a pressure patch, bandage contact lens, bio-adhesive agent, or suture closure. The patient should be started on a topical antibiotic and a cycloplegic agent until the anterior chamber re-forms and the wound secures. If lenticulocorneal touch has developed, the wound must be immediately closed and the anterior chamber re-formed with balanced salt solution to avoid corneal decompensation. It should be noted that a flat anterior chamber can also occur secondary to aqueous misdirection, choroidal hemorrhages, and choroidal effusions, all of which may develop as a complication of the initial surgical procedure. Small choroidal effusions can be observed. Moderate to severe choroidal effusions may require systemic steroids and/or surgical drainage.

Hyphema

Persistent bleeding from iris or ciliary body vessels can lead to hyphema formation. The hyphema is typically self-limiting and usually does not require treatment.

Cataract

Disruption of the capsule integrity can cause the lens to hydrate and lead to cataract formation. Cataracts can also occur as a result of anterior chamber flattening, lenticulocorneal touch, and chronic inflammation. Even when definite evidence of direct lens trauma from surgery is lacking, eyes that have had a peripheral iridectomy appear to be at increased risk for progressive cataract formation.[51-54]

Persistently elevated IOP

The IOP may remain elevated despite a surgical peripheral iridectomy if the iridectomy is imperforate, synechial angle closure is present, the iridectomy is blocked by vitreous, plateau iris syndrome is present, or malignant glaucoma develops. A re-operation or adjunctive laser treatment is indicated if the iridectomy is imperforate or blocked by vitreous. Intraoperative gonioscopy should be performed to identify areas of synechial closure which may be treated at the same time by goniosynechialysis. Synechiae that have been present for more than 6 months to a year may damage the trabecular meshwork rendering synechialysis ineffective, thus necessitating a filtration surgery.

Miscellaneous

Key Features: Surgical Iridectomy - Postoperative Complications

  

.   

Wound lead and associated sequelae

  

.   

Flat anterior chamber

  

.   

Choroidal effusion

  

.   

Hypotomy

  

.   

Cataract formation

  

.   

Peripheral anterior synechiae formation

  

.   

Hyphema

  

.   

Aqueous misdirection

  

.   

Endophthalmitis

  

.   

Visual disturbances

  

.   

Diplopia

  

.   

Photophobia

  

.   

Glare

Endophthalmitis, as well as all the complications of intraocular surgery may occur, although they are extremely rare. Complaints of uniocular diplopia, photophobia, and glare have been reported.[50,55]

 

 

OTHER SURGICAL PROCEDURES

SECTOR IRIDECTOMY

A sector iridectomy should be considered instead of a peripheral iridectomy when there is a need for a large optical opening. This may be the situation when the visual axis is occluded by a membrane, the pupil is displaced, or visual access to the retinal periphery is necessary for examination or treatment of retinal disease. The procedure is similar to performing a peripheral iridectomy, except that the initial entry incision is larger to allow the iris to be grasped close to the pupillary margin. The iris is then withdrawn until the pupillary margin is exposed. Alternatively, after the iris has prolapsed, a hand-over-hand technique may be used until the sphincter has been exteriorized. Excision of the iris is performed with a single cut (Fig. 219.11).

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FIGURE 219.11  Excision of the iris for a sector iridectomy.

 

 

 

 

SURGICAL GONIOSYNECHIALYSIS

Current techniques for performing goniosynechialysis stemmed from the modernized method described by Campbell and Vela in 1984.[56] Their technique relied on direct visualization of the chamber angle that was facilitated by an iatrogenically deepened and maintained anterior chamber. This allowed for the safe insertion of a cyclodialysis spatula and subsequent cleavage of the synechiae from their anterior attachments. Their small case series provided evidence that goniosynechialysis could be effective in reducing IOP. Further studies by both Shingleton et al[57] and Tanihara et al[58] provided further evidence that surgical goniosynechialysis effectively reduces the degree of synechiae, either alone or in conjunction with other surgical procedures, and lowers IOP.

The surgical procedure can be divided into three stages: (1) anterior chamber deepening, (2) intraoperative gonioscopy, and (3) lysis of iris adhesions using a cyclodialysis spatula. The preoperative preparation and anesthesia is the same as that for the surgical iridectomy. Deepening of the anterior chamber is instituted by first removing the aqueous from the anterior and posterior chambers. This is achieved by creating a beveled temporal paracentesis. Application of pressure to the posterior lip of the wound allows for egress of the anterior chamber aqueous. A gentle massage ?360° of the limbus with a muscle hook encourages aqueous from the posterior chamber to flow into the anterior chamber. This fluid can then be expressed from the eye by again applying pressure to the posterior lips of the paracentesis. The anterior chamber is then deepened by injecting a viscoelastic agent into the anterior chamber through the paracentesis with a blunt cannula.

Gonioscopy is then performed to determine the degree and location of synechial closure using a Koeppe or Barkan lens. Under direct visualization, a curved irrigating cyclodialysis spatula is inserted into the previously placed temporal paracentesis site to treat any synechiae present in the nasal angle. Separation of the peripheral anterior synechiae is achieved by gently depressing the peripheral iris next to the synechiae in an anterior-to-posterior movement. Care is taken to avoid creating an iatrogenic angle recession or cyclodialysis cleft. If synechiae are present temporally, an additional paracentesis is made nasally whereby the cyclodialysis spatula can be passed to treat the temporal angle. Following completion of the synechialysis, it is imperative to remove the viscoelastic agent to avoid spikes in IOP. This is easily achieved by irrigating the anterior chamber with balanced salt solution and forcing the viscoelastic out through the paracentesis. Postoperative success rates may be enhanced by combining the synechialysis with cataract extraction and/or performing diode laser peripheral iridoplasty in the early postoperative period.[59-61]

Although rare, potential complications of goniosynechialysis include minor intraoperative hemorrhage, exudation of fibrin, transient IOP spike, and inadvertent cyclodialysis cleft formation.

 

 

SUMMARY

There are a variety of clinical conditions that require the creation of a peripheral iris hole to facilitate passage of aqueous from the posterior chamber into the anterior chamber. Although useful, the surgical iridectomy has been replaced by the less invasive and equally effective laser iridotomy. Despite the widespread use of lasers, it is important to know the steps for performing a surgical iridectomy or sector iridectomy due to conditions that may hinder iridotomy creation. Both surgical goniosynechialysis and argon laser gonioplasty serve as useful adjuncts to iridotomies/iridectomies.

 

 

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