Lisa S. Gamell, MD; Alexander Zabaneh, MD; and Cristan M. Arena, MD
Argon laser iridoplasty (also called gonioplasty) was first described by Hager in 1973, who used the procedure to coagulate the iris base and deepen a narrow angle. Since that time, it has been described to widen the angle in a variety of syndromes. Typically, the contraction burns are applied to the peripheral iris with an argon laser, thereby thinning the peripheral iris tissue. The iris then shrinks away from the angle structures, ideally fostering outflow.
Iridoplasty can be performed when a laser peripheral iridotomy (LPI) is not possible, in eyes that have a narrow angle despite the presence of a patent iridotomy, in eyes with narrow angles due to mechanisms other than pupillary block, or in the presence of narrow angles with peripheral anterior synechiae (PAS).
In this chapter, each of these indications will be described in detail, as will contraindications, technique, postoperative management, and postoperative complications.
INDICATIONS
Acute Angle Closure
One of the first things learned in residency is that LPI is the definitive treatment for acute primary angle-closure glaucoma (PACG) because it reverses pupillary block. However, in order to perform this procedure in a more facile manner, it is necessary to break the attack by first lowering intraocular pressure (IOP). This allows the edematous cornea to clear, but also allows for patient comfort. Breaking an attack of PACG is usually accomplished both with topical ocular hypotensives and systemic medication, such as carbonic anhydrase inhibitors and/or hyperosmotics.
Argon laser peripheral iridoplasty (ALPI) is valuable in that it can open the angle mechanically in PACG resistant to medical therapy. During an attack, the iris is apposed to the trabecular meshwork. Iridoplasty can contract the iris adequately to pull it away from the meshwork.1 In addition, a recent prospective trial that randomized patients to either immediate ALPI or conventional systemic medical therapy (acetazolamide and mannitol) revealed that ALPI can be an effective alternative to conventional medical therapy in lowering IOP in PACG.2 Furthermore, argon laser iridoplasty may be successful in treating angle-closure glaucoma unrelieved despite a patent laser iridotomy.3
It should be stressed that the definitive procedure to break pupillary block once IOP is controlled and the cornea is clear is indeed LPI.
Chronic Angle Closure
Chronic angle-closure glaucoma (CACG) may develop in 2 ways. The first is in eyes that have suffered an attack of PACG and residual angle closure leads to PAS formation. The second is in eyes with angles that slowly narrow over time, usually asymptomatically, and IOP rises slowly as the angle is compromised. The latter is more common.4
In patients who have suffered an attack of PACG and have residual angle closure and PAS, iridoplasty can be used. If PAS are of less than 1-year duration, there is a 50% chance of restoring outflow function to the affected portion of the angle, but best results are achieved if PAS have been present for less than 6 months. Anecdotal evidence suggests that PAS of up to 1-year duration can be broken with iridoplasty.5 This has not been reproducible, and iridoplasty is rarely successful if the PAS have been present for more than 1 year. These may require surgical intervention, such as goniosynechialysis.6,7
In those patients with the second type of CACG, the initial procedure performed should be LPI. However, occasionally, LPI alone is insufficient to open the angle and prevent apposition. In this situation, laser peripheral iridoplasty is a useful adjunct to open the angle. Areas of apposition may be successfully treated as iris contraction mechanically pulls open the angle, thus helping to prevent PAS formation. Iridoplasty may be successful even after the development of PAS.5
Lens-Induced Angle Closure
Angle-closure glaucoma can be the result of the size or position of the lens. Iridoplasty can be used in eyes with narrow angles from gradually enlarging lenses without significant visual dysfunction. This can delay the need for lens extraction; however, if the cataract is visually significant or the angle is unresponsive to iridoplasty, cataract extraction should be performed.
In conditions such as phacomorphic glaucoma or anterior subluxation of the lens, lens extraction is indeed the definitive treatment needed. Nevertheless, like other types of angle-closure glaucoma, corneal edema and inflammation may preclude this procedure. In eyes that do not respond to medical therapy and laser iridotomy, iridoplasty can be used to eliminate appositional closure until such time as cataract surgery can be performed.6
Plateau Iris Syndrome
Plateau iris describes an abnormal iris configuration in which angle-closure glaucoma occurs without pupillary block. Plateau iris configuration describes the gonioscopic appearance of a closed angle but flat iris plane and deep central anterior chamber. Abnormal ciliary processes are most often responsible for this condition. On ultrasound biomicroscopy, the ciliary processes are anteriorly positioned and shortened, which in turn result in a more anterior insertion of the iris and crowding of the angle. Most of these cases may be treated with LPI. Plateau iris syndrome results when such an angle is persistently narrow despite a patent iridotomy, resulting in IOP elevation after pupillary dilation.8 About 20% of Japanese patients with primary angle closure and PACG, who also had a patent peripheral iridotomy, had findings of plateau iris on ultrasound biomicroscopy.9 Miotics such as pilocarpine may be initially effective in keeping the angle open, but over time, synechiae may still develop. Iridoplasty can help prevent synechial angle closure in these patients.10
Laser Trabeculoplasty
Laser peripheral iridoplasty can be used to pull the iris away from the trabecular meshwork and increase visibility, thus permitting laser trabeculoplasty.1,6
Nanophthalmos
Nanophthalmos is a rare condition in which an otherwise normal eye has a small volume, small equatorial diameter, and small corneal diameter. The lens is normal in size, however, which results in shallowing of the anterior chamber and narrowing of the angle. The condition has been described to follow certain stages. In stage 1, the angle is narrow, and IOP is normal. In stages 2 and 3, the angle appears more narrow and becomes partially closed. Once stage 4 is reached, angle closure is present, and IOP is elevated but controllable with medications. At stage 5, synechial angle closure is present, and IOP is no longer controllable with medications. Early LPI is the treatment of choice, preferably in stage 1 or 2, to prevent angle closure. If the angle continues to narrow or remains narrow despite a patent iridotomy, laser iridoplasty is used to open the angle. It may be repeated if necessary. In addition, once stage 3 or 4 is reached, iridoplasty may be a useful adjunct to iridotomy. If a nanophthalmic eye reaches stage 5, it will most likely need surgery to control IOP. Therefore, given the complications of surgery in nanophthalmos, such as choroidal effusion and serous retinal detachment, early diagnosis and aggressive treatment with LPI and iridoplasty are of utmost importance.1,6
Topiramate-Induced Angle Closure
Topiramate was first approved by the US Food and Drug Administration as an antiepileptic in partial-onset seizures and primary generalized tonic-clonic seizures in 1996. In 2004, it received approval for the prophylaxis of migraine headaches. With this indication, use of topiramate increased.
Topiramate has been associated with a syndrome in which supraciliary effusion causes anterior displacement of the lens-iris diaphragm, with resultant acute myopia and secondary angle closure. Symptoms typically occur within 1 month of initiating therapy. In contrast to PACG, which is rare in individuals younger than 40 years, secondary angle-closure glaucoma associated with topiramate has been reported in pediatric patients as well as adults. Furthermore, while bilateral acute PACG is rare, topiramate usually affects both eyes.11
First and foremost, topiramate must be discontinued. Pilocarpine is contraindicated in this situation, as it can promote further anterior displacement of the lens-iris diaphragm. Topical and oral medications to lower IOP are initiated, and cycloplegic agents can be used in an attempt to shift the lens-iris diaphragm posteriorly. It is important to note that pupillary block does not play a role in this situation; thus, an LPI would be unsuccessful in breaking the attack.
There have been reported cases of laser peripheral iridoplasty being effective in topiramate-associated bilateral acute angle-closure glaucoma. In one series, the IOP was markedly reduced and the anterior chamber deepened after several hours of ineffective medical therapy in 4 patients.12 Another report demonstrated ALPI to open the angle within 1 hour after treatment.13
Vitreoretinal Procedures
Certain vitreoretinal procedures, such as scleral buckling and panretinal photocoagulation, can lead to ciliary body edema. Ciliary body edema causes anterior lens displacement and narrowing of the angle. Iridoplasty can be used to treat angle closure in these situations.6
Uveitis-Induced Angle Closure
One case has been reported in the European literature of a patient with uveitic acute closure who responded to ALPI after medical treatment and laser iridotomy failed to break the attack. In this situation, iridoplasty broke posterior synechiae, opened the angle, and reduced the IOP.14
Iris and Pupil Configuration
Iris configuration can affect visual function after intraocular lens implantation, especially with multifocal lenses. When the iris is encroaching on the intraocular lens, causing a decentration of the lens, ALPI can be applied to the mid-peripheral iris. This allows for better centration of the intraocular lens and has been shown to improve subjective and objective visual acuity and quality.15
Iridoplasty has also been used for cobblestone iris configuration induced angle closure and iris obstruction of Boston keratoprosthesis, with reported success.16,17
CONTRAINDICATIONS
Poor Visualization
In PACG, the cornea is often edematous, precluding an adequate view of the iris to allow for laser treatment, both iridotomy and iridoplasty. In this case, laser treatment of any kind may further damage the cornea.
Flat Anterior Chamber
Similarly, performing iridoplasty in the setting of a flat anterior chamber can result in endothelial burns and irreparable corneal damage.
PRACTICAL CONSIDERATIONS FOR ARGON LASER PERIPHERAL IRIDOPLASTY
Lisa S. Gamell, MD
In many patients with occludable angles after laser iridotomy, there may be some component of phacomorphic block occurring due to the increased thickness of the cataractous lens. Certainly, in patients with visually significant cataracts, who are viable candidates for surgery, a reasonable choice might be to proceed with cataract surgery; this would relieve the phacomorphic component, and hopefully restore functional angle anatomy, as long as PAS have not formed (Figures 58-1 and 58-2).
In patients who are poor surgical candidates, or in whom cataracts are not yet visually significant—and where the benefits do not outweigh the risks of surgery—ALPI is a reasonable option for treating residual angle closure. It is preferable to treat with ALPI before PAS formation is apparent. Note, however, that if IOP starts to rise despite medical therapy or angle anatomy is seriously compromised, then lens extraction should be seriously considered.
Figure 58-1. Gonioscopic view of closed angle prior to phacoemulsification.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
