Long-term evaluation of the use of Ahmed gonioimplants in dogs with primary glaucoma: nine cases (2000–2008)

Abstract

In dogs with medically refractory primary glaucoma, placement of a gonioimplant appears to be effective in maintaining vision.

Surgical Treatment of Canine Glaucoma

“…Hypotony is usually more commonly reported with nonvalved devices, 9 but poor flow control caused by excessive peritubular filtration at the anterior chamber site can also occur in valved devices. 44,45 Hypotensive retinopathy with multifocal retinal folds has been described in dogs and people undergoing glaucoma filtering surgery, 14,46 and shallow anterior chamber (15%, 17% of the cases), choroidal effusion (13%, 14%), and corneal decompensation (7%, 14%) have also been reported in a large study on human patients implanted with Ahmed and Baerveldt devices, respectively. 20 Inadequate placement of the tube may result in corneal endothelial damage and edema caused by its excessive length, its obstruction by the base of the iris when trimmed too short, or its displacement secondary to failure of the securing sutures.…”

“…3). [7][8][9][10][11][12][13][14][15] The subconjunctival space is the most common site for AH diversion, but experimental studies have investigated other possible outlets, such as the jugular vein via the facial vein, the subcutaneous space, and the parotid duct, with limited to no success. 16,17 The Cullen shunt to the frontal sinus has also been described.…”

“…Topical corticosteroids, administered every 6 to 8 hours, not only aid in addressing the anterior uveitis postintracameral penetration, 1 but may help in suppressing the cyclooxygenase pathway and inhibiting fibroblasts proliferation, both responsible for implant fibrosis. 14,28,29 Several studies support the use of systemic corticosteroids to limit capsular fibrosis and achieve better IOP control in the human field [30][31][32] ; however, a report of the American Academy of Ophthalmology has recently disproved the claim. 33 Despite this current debate, systemic corticosteroids are currently recommended, when possible, in veterinary ophthalmology.…”

“…1 Topical corticosteroids are tapered over the course of several weeks; however, long-term treatment with topical prednisolone acetate 1% every 24 to 48 hours is warranted. 14 Topical and systemic antibiotics are administered for 2 weeks postoperatively. Topical antiglaucoma medications are typically maintained long-term.…”

“…The rationale behind this is that cyclodestruction causes massive release of intraocular inflammatory mediators and postoperative increases in IOP, with increased amount of cytokine-laden AH outflow through the implant, likely leading to its premature fibrosis. 14,35 For this reason, several studies have suggested a staggered two-stage technique, with early Ahmed gonioimplantation followed by later TSCP or ECP. [35][36][37] ECP allows direct visualization and optimal laser energy delivery, resulting in decreased intraocular inflammation when compared with TSCP.…”