Laser Treatment for Glaucoma

Abstract

An iridotomy, or opening in the iris, can be created with a laser to treat or prevent pupillary block without having to perform incisional surgery. Laser iridectomies are most commonly performed with argon or Nd:YAG lasers. Here the term iridectomy will refer to the procedure used to create an iris opening by laser, and iridotomy will refer to the iris opening itself. •Primary acute and chronic angle-closure glaucoma (also combined-mechanism): Laser iridectomy is performed to relieve acute pupillary block (to break an acute attack of primary angle closure glaucoma) or as part of management of chronic angle-closure glaucoma concomitantly with medical therapy. •Pseudophakic/aphakic pupillary block glaucoma and other secondary forms of pupillary block glaucoma (i.e., uveitis, following retinal surgery) Incomplete surgical iridectomy •Prophylaxis for narrow angle configuration: Performed when the eye is considered at risk for pupillary block (acute angle-closure glaucoma) as determined by gonioscopy or because of an angle-closure attack in the fellow eye •Pigment dispersion glaucoma: Posterior bowing of the iris with “reverse pupillary block” configuration is often noted in pigmentary glaucoma, which possibly causes increased pigment release from contact between zonules and the posterior iris. Laser iridectomy may minimize the degree of posterior bowing. •Diagnostic: Occasionally an iridectomy may be indicated to ensure pupillary block is not a contributing factor to angle closure in cases where it is not thought to be the primary mechanism (such as in plateau iris). •Caution should be used in eyes with rubeosis irides and in patients on systemic anticoagulation due to risk of hyphema. Argon laser, which coagulates blood vessels, may be more appropriate than Nd:YAG laser in these settings. •Challenges include: •Corneal edema in angle closure glaucoma: May use topical glycerin to improve edema •Shallow anterior chamber: Locate iris crypts where iris is thinnest. •Engorged iris: Avoid large blood vessels; use argon laser first. •Thick iris stroma •For information on medications, •Performed at slit lamp •Lenses: Special iridectomy lenses allow better control of eye movement, aid in eyelid retraction, facilitate delivery of laser energy to the iris, and may prevent corneal burns by acting as heat-sinks.