Iridotomy to slow progression of visual field loss in angle‐closure glaucoma

Background Primary angle‐closure glaucoma is a type of glaucoma associated with a physically obstructed anterior chamber angle. For example, contact between the iris and lens at the pupillary margin creates a pupillary block that increases resistance to aqueous outflow. Obstruction of the anterior chamber angle blocks drainage of fluids (aqueous humor) within the eye and may raise intraocular pressure (IOP). Elevated IOP is associated with glaucomatous optic nerve damage and visual field loss. Laser peripheral iridotomy ('iridotomy') is a procedure to eliminate pupillary block by allowing aqueous humor to pass directly from the posterior to anterior chamber, which is achieved by creating a hole in the iris using laser. Iridotomy is used to treat patients with primary angle‐closure glaucoma, patients with primary angle‐closure (narrow angles and no signs of glaucomatous optic neuropathy), and patients who are primary angle‐closure suspects (patients with reversible obstruction). However, the effectiveness of iridotomy on slowing progression of visual field loss is uncertain. Objectives To assess the effects of iridotomy compared with no iridotomy for primary angle‐closure glaucoma, primary angle‐closure, and primary angle‐closure suspect. Search methods We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2021, Issue 10), which contains the Cochrane Eyes and Vision Trials Register; MEDLINE Ovid; Embase Ovid; PubMed; LILACS; ClinicalTrials.gov; and the WHO ICTRP. The date of the most recent search was 10 October 2021. Selection criteria Randomized or quasi‐randomized controlled trials that compared iridotomy with no iridotomy in primary angle‐closure suspects, people with primary angle‐closure, or people with primary angle‐closure glaucoma in one or both eyes were eligible. Data collection and analysis We used standard Cochrane methodology and assessed the certainty of the body of evidence for prespecified outcomes using the GRADE approach. Main results We identified four studies (3086 eyes of 1543 participants) that compared iridotomy with no iridotomy in participants (range of mean age 59.6 to 62.9 years) who were primary angle‐closure suspects from China, Singapore, or the UK. Study investigators randomized one eye of each participant to iridotomy and the other to no iridotomy. Two studies provided long‐term (five or more years) results. We judged the certainty of the evidence as moderate to low across the prespecified outcomes, downgr