Aqueous shunts for glaucoma

Minckler D, Vedula SS, Li T, Mathew M, Ayyala R, Francis B

Published Online:

January 21, 2009

Glaucoma is a leading cause of blindness worldwide. Treatments for glaucoma include the use of eye drops, laser treatment, and a variety of surgical operations. Surgery is usually considered only after eye drops and lasers have proven to be ineffective. Among surgical operations, aqueous shunts or glaucoma drainage devices which come in a variety of sizes and shapes are often used in complicated cases when traditional types of surgery such as trabeculectomy (making a cleft in the eye wall) have not worked. The typical aqueous shunt includes a tiny rubber tube (drain) that connects the eye fluid chamber to a plate that is attached to the eye wall. The plate or explant stimulates the formation by the body of a space into which eye fluid can drain. This review summarizes previously published randomized and quasi-randomized controlled trial results for aqueous shunts (studies that compare treatment with no treatment or to alternative treatments including a control group). We included 15 trials involving 1153 participants with varied diagnoses of glaucoma. At present there is insufficient evidence to conclude that clinical outcomes of trabeculectomy differ substantially from those of aqueous shunts in similar patients with complicated glaucomas. There is also insufficient evidence to conclude that any specific aqueous shunt is superior to the others currently in widespread use.

Abstract (click to read)

Background:

Aqueous shunts are employed for intraocular pressure (IOP) control in primary and secondary glaucomas that fail medical, laser, and other surgical therapies.

Objectives:

This review compares aqueous shunts for IOP control and safety.

Search strategy:

We searched CENTRAL, MEDLINE, PubMed, EMBASE, NRR in January 2006, LILACS to February 2004 and reference lists of included trials.

Selection criteria:

We included all randomized and quasi-randomized trials in which one arm of the study involved shunts.

Data collection and analysis:

Two authors independently extracted data for included studies and a third adjudicated discrepancies. We contacted investigators for missing information. We used fixed-effect models and summarized continuous outcomes using mean differences.

Main results:

We included fifteen trials with a total of 1153 participants with mixed diagnoses. Five studies reported details sufficient to verify the method of randomization but only two had adequate allocation concealment. Data collection and follow-up times were variable.

Meta-analysis of two trials comparing Ahmed implant with trabeculectomy found trabeculectomy resulted in lower mean IOPs 11 to 13 months later (mean difference 3.81 mm Hg, 95% CI 1.94 to 5.69 mm Hg). Meta-analysis of two trials comparing double-plate Molteno implant with the Schocket shunt was not done due to substantial heterogeneity. One study comparing ridged with standard double-plate Molteno implants found no clinically significant differences in outcome. Two trials investigating the effectiveness of adjunctive mitomycin (MMC) with the Molteno and Ahmed implants found no evidence of benefit with MMC. Two trials that investigated surgical technique variations with the Ahmed found no benefit with partial tube ligation or excision of Tenon's capsule. One study concluded there were outcome advantages with a double versus a single-plate Molteno implant and one trial comparing the 350 mm2 and 500 mm2 Baerveldt shunts found no clinically significant advantage of the larger device but neither of these trials included all patients randomized. One study suggested improved clinical outcome when MMC was employed with a newly described shunt including ultrasound supporting the conclusion. One small study did not demonstrate an outcome advantage to systemic steroid use postoperatively with single-plate Molteno shunts. One study comparing endocyclophotocoagulation (ECP) with Ahmed implant in complicated glaucomas found no evidence of better IOP control with Ahmed implant over ECP.

Authors' conclusions:

Relatively few randomized trials have been published on aqueous shunts and methodology and data quality among them is poor. To date there is no evidence of superiority of one shunt over another.

This record should be cited as:

Minckler D, Vedula SS, Li T, Mathew M, Ayyala R, Francis B. Aqueous shunts for glaucoma. Cochrane Database of Systematic Reviews 2006, Issue 2. Art. No.: CD004918. DOI: 10.1002/14651858.CD004918.pub2

Assessed as up to date:

January 31, 2006

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Primary Review Group:

Eyes and Vision Group

Health topics:

Eyes & vision > Glaucoma > Open angle

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