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Editors Selection IGR 17-3

Surgical treatment: Aqueous drainage devices

Comment by Steven Gedde on:

57192 Effect of Early Treatment with Aqueous Suppressants on Ahmed Glaucoma Valve Implantation Outcomes, Pakravan M; Rad SS; Yazdani S et al., Ophthalmology, 2014; 121: 1693-1698

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Pakravan and colleagues conducted a randomized clinical trial to evaluate the effect of early treatment with aqueous suppressants on the outcomes of Ahmed glaucoma valve (AGV) implantation. Patients undergoing AGV surgery were randomized to receive timolol- dorzolamide fixed-combination drops twice daily when the intraocular pressure (IOP) exceeded ten mmHg, or conventional medical therapy. A stepwise regimen of glaucoma medications was used in both study groups to maintain IOP at a target level of 15 mmHg or less. Mean IOP was lower in the group with early aqueous suppressant treatment at 54 weeks (14.0 mmHg vs 16.8 mmHg, p = 0.012), despite a similar mean number of glaucoma medications (1.8 vs 1.6, p = 0.184). The success rate (6 mmHg < IOP < 15 mmHg and ≥ 30% reduction from baseline) was higher in the group receiving early medical treatment at one year (63.2% vs 33.3%, p = 0.008). The frequency of a hypertensive phase (IOP > 21 mmHg in first three months postoperatively) was reduced in the early treatment group (20.4% vs 66.0%, p < 0.001), but no significant difference was observed in the rate of choroidal effusions or other complications between study groups. The capsule surrounding the end plate of a glaucoma drainage implant offers the major resistance to aqueous outflow through the device. An early exposure of the plate to aqueous humor rich in inflammatory mediators could contribute to the development of a thicker capsule. A higher hydrostatic pressure within the bleb cavity may also compress and compact the capsule, resulting in decreased permeability. Early treatment with aqueous suppressants after AGV implantation may beneficially influence surgical outcomes by reducing the level of inflammatory mediators delivered to the plate and/or decreasing the hydrostatic pressure in the bleb with less compression of the capsule.

Early treatment with aqueous suppressants after AGV implantation may beneficially influence surgical outcomes by reducing the level of inflammatory mediators delivered to the plate and/or decreasing the hydrostatic pressure in the bleb with less compression of the capsule

Subjects enrolled in the study were relatively young (mean age 44 years), and only 2.1% had primary open-angle glaucoma. This is not a typical population undergoing glaucoma surgery and could affect the generalizability of findings. The target pressure of 15 mmHg in the study may have been more aggressive than needed and resulted in overtreatment in some patients. Subdividing subjects into qualified and complete successes is less meaningful, given the different criteria for use of medical therapy between study groups. The AGV is a valved implant, and study results may not be applicable to non-valved implants that delay aqueous humor delivery to the end plate. Despite these limitations, the authors are to be congratulated for adding important information to the medical literature regarding glaucoma drainage implants.

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