Balyeat HD. Cataract surgery in the glaucoma patient. Part 1: A cataract surgeon’s perspective. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 1998, module 3.
Friedman DS, Jampel HD, Lubomski LH, et al. Surgical strategies for coexisting glaucoma and cataract: an evidence-based update. Ophthalmology. 2002;109(10):1902–1913.
Jampel HD, Friedman DS, Lubomski LH, et al. Effect of technique on intraocular pressure after combined cataract and glaucoma surgery: an evidence-based review. Ophthalmology. 2002;109(10):2215–2224.
Jin GJ, Crandall AS, Jones JJ. Phacotrabeculectomy: assessment of outcomes and surgical improvements. J Cataract Refract Surg. 2007;33(7):1201–1208.
Skuta GL. Cataract surgery in the glaucoma patient. Part 2: A glaucoma surgeon’s perspective. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 1998, module 4.
Weinreb RN, Mills RP, eds. Glaucoma Surgery: Principles and Techniques. 2nd ed. Ophthalmology Monograph 4. San Francisco: American Academy of Ophthalmology; 1998:65–85.
Surgery for Angle-Closure Glaucoma
The first clinical decision to be made following diagnosis of angle-closure glaucoma (ACG) is whether angle closure is due to pupillary block or another mechanism. The treatment of angle closure due to pupillary block, whether primary or secondary, is a laser iridotomy or an incisional iridectomy. These procedures provide an alternate route for aqueous trapped in the posterior chamber to enter the anterior chamber, which then allows the iris to recede from its occlusion of the trabecular meshwork (Fig 8-13). Laser surgery has become the preferred method in almost all cases. Both the argon laser and the Nd:YAG laser are effective, but the Nd:YAG laser has become the more popular instrument to use. Cataract extraction is also effective as therapy for angle closure secondary to pupillary block. Following the successful resolution of pupillary block, IOP may return to normal or may remain elevated. At this point, the indications for surgery become similar to those for POAG, except for possible surgical goniosynechialysis. When cataract surgery will result in aphakia or anterior chamber intraocular lens placement, a surgical iridectomy should be performed at the time of the cataract surgery.
Figure 8-13 Angle-closure glaucoma (top). Laser iridotomy or surgical iridectomy breaks the pupillary block and results in opening of the entire peripheral angle (bottom) if no permanent peripheral anterior synechiae are present. (Reproduced and
modified with permission from Kolker AE, Hetherington J, eds. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas. 5th ed. St Louis: Mosby; 1983.)
For eyes with secondary angle closure not caused by pupillary block, the ophthalmologist should attempt to identify and treat underlying conditions before surgery. For example, an eye with rubeosis iridis from diabetic retinopathy should be treated with panretinal photocoagulation and consideration should be given to intravitreal injection of an antivascular endothelial growth factor (anti-VEGF) agent prior to glaucoma surgery. In early cases, the IOP elevation may be reversible. Even in the presence of complete synechial angle closure from rubeosis, neovascularization may regress following panretinal photocoagulation, allowing subsequent successful filtering surgery and reducing the risk of hyphema.
Laser Iridotomy
Indications
The indication for iridotomy is the presence of pupillary block. However, it is sometimes necessary to perform iridotomy for diagnostic as well as therapeutic purposes. For example, the diagnosis of plateau iris can be confirmed only when a patent iridotomy fails to change the peripheral iris configuration and relieve angle closure. Laser iridotomy is also indicated to prevent pupillary block in an eye considered to be at risk of this condition, based on gonioscopic findings or an angleclosure attack in the fellow eye.
Contraindications
An eye with active rubeosis iridis may bleed following laser iridotomy. The risk of bleeding is also increased in a patient taking systemic anticoagulants, including aspirin. The argon laser may be more appropriate than the Nd:YAG, should laser iridotomy be performed in such an individual.
Preoperative considerations
In the setting of acute angle closure, it is often difficult to perform laser iridotomy because of the cloudy cornea, shallow chamber, and engorged iris. The clinician should attempt to break the attack medically and then proceed to surgery. Corneal edema may be improved prior to laser iridotomy by pretreatment with topical glycerin. It is easiest to penetrate the iris in a crypt. The surgeon should take care to keep the iridotomy in the peripheral iris and covered by eyelid, if possible, or at the 3- or 9- o’clock position, to avoid monocular diplopia. Pretreatment with pilocarpine may be helpful by stretching and thinning the iris. Pretreatment with apraclonidine or brimonidine can help blunt IOP spikes.
Technique
The argon laser may be used for performing iridotomy in most eyes, but very dark and very light irides present technical difficulties. With a condensing contact lens, the typical initial laser settings are 0.1 second of duration, 50-µm spot size, and 800–1000 mW of power. There are a number of variations in technique, and iris color dictates which technique is chosen. Complications include localized lens opacity, acute rise in IOP (which may damage the optic nerve), transient or persistent iritis, early closure of the iridotomy, posterior synechiae, and corneal and retinal burns.
Iridotomy performed with the Q-switched Nd:YAG laser is preferred for most eyes. A patent iridotomy created with the Q-switched Nd:YAG laser generally requires fewer pulses and less energy than one created with an argon laser. Also, the effectiveness of the Q-switched Nd:YAG laser is not affected by iris color, and the iridotomy created by this laser does not close as often over the long term as one created by argon laser. With a condensing contact lens, the typical initial setting for the Q-switched Nd:YAG laser is 2–8 mJ. Potential complications include disruption of the anterior lens
capsule or corneal endothelium, bleeding (usually transient), postoperative IOP spike, inflammation, and delayed closure of the iridotomy. To prevent damage to the lens, the surgeon must use caution with the Q-switched Nd:YAG laser when further enlarging the opening once patency has been established. The site of the iridotomy should be as peripheral as possible. Some authors advocate placing the iridotomy at the 3- or 9-o’clock position to minimize the risk of linear dysphotopsias.
Postoperative care
Bleeding may occur from the iridotomy site, particularly with use of the Nd:YAG laser. Often, compression of the eye with the laser lens will tamponade the vessel, thereby slowing bleeding until coagulation can occur. In rare cases when this does not work, it may be helpful to use the argon laser to coagulate the vessel. Postoperative spikes in IOP may occur, as with LTP, and they are treated as described in the section on LTP. Inflammation is treated as necessary with topical corticosteroids.
Murphy PH, Trope GE. Monocular blurring: a complication of YAG laser iridotomy. Ophthalmology. 1991;98(10):1539–1542. Ritch R, Shields MB, Krupin T, eds. The Glaucomas. 2nd ed. St Louis: Mosby; 1996.
Shields MB. Textbook of Glaucoma. 4th ed. Philadelphia: Williams & Wilkins; 2000.
Spaeth GL, Idowu O, Seligsohn A, et al. The effects of iridotomy size and position on symptoms following laser peripheral iridotomy. J Glaucoma. 2005;14(5):364–367.
Laser Gonioplasty, or Peripheral Iridoplasty
Indications
Gonioplasty, or iridoplasty, is a technique to deepen the angle. It is primarily used in angle-closure glaucoma resulting from plateau iris. Stromal burns are created with the argon laser in the peripheral iris to cause contraction and flattening.
Contraindications
The contraindications are the same as those for laser iridotomy.
Preoperative considerations
An angle that is closed from plateau iris will not open with creation of a laser iridotomy, because the underlying mechanism is not pupillary block. Anterior segment ultrasonography may be helpful in making this diagnosis.
Technique
Typical laser settings for the argon green laser are 0.1–0.5 second duration, 200to 500-µm spot size, and 200–500 mW of power. Laser gonioplasty can be used to open the angle temporarily, in anticipation of a more definitive laser or incisional iridectomy, or in other types of angle closure, such as plateau iris syndrome and nanophthalmos.
Ritch R, Tham CC, Lam DS. Argon laser peripheral iridoplasty (ALPI): an update. Surv Ophthalmol. 2007;52(3):279–288.
Postoperative considerations
Elevated IOP may occur in the postoperative period and should be monitored, as is done after other laser procedures. Anisocoria and iris pigment changes may also be noted. The clinician should mention this possibility to the patient during the preoperative consent process.