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H. A. Khaja, D. O. Hodge, A. J. Sit; Trabectome Ablation Arc Clinical Results and Relation to Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4191.
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The Trabectome is a novel device for performing ab interno goniotomy for the treatment of open angle glaucoma. The procedure differs from traditional goniotomies in that the trabecular meshwork (TM) and inner wall of Schlemm’s canal (SC) are not incised, but ablated with electrocautery. The purpose of this study is to determine if the amount of tissue ablation is associated with the degree of intraocular pressure (IOP) lowering and reduction of glaucoma medications.
The medical records of subjects who had undergone Trabectome surgery at the Mayo Clinic between Sept 2006-Aug 2007 and were at least 3 months from their initial surgery date were reviewed. Stereoscopic gonioscopy photographs were obtained for 360 degrees of the corneoscleral angle in each eye which had undergone surgery. Photographic montages were used to reconstruct a single image of the entire angle for each eye. The areas in which the TM and SC remained visibly open (ablation arc) were identified using the montages in conjunction with the stereoscopic photographs. Generalized estimating equation models were used to determine the correlation between the size of the ablation arc in degrees, and the amount of IOP lowering and reduction in number of medications.
Fifty-seven patients underwent Trabectome surgery between September 1, 2006 and August 31, 2007. Seven of 57 patients underwent bilateral surgery and two required a second Trabectome surgery yielding 66 unique procedures. Of these 66% were combined with cataract extraction. 28 eyes of 26 patients were photographed and analyzed. The mean ablation arc for the 28 available eyes was 87.0 ± 29.1 degrees (mean ± SD) at a mean of 6.9 ± 3.3 months after surgery. The pre operative IOP was 20.4 ± 9.7 and final post operative IOP was 15.4 ± 6.1 yielding a mean decrease in IOP of 5.06 ± 9.4 (p<0.001). There was a reduction in the number of IOP lowering medications from 2.6 ± 0.9 to 1.1 ± 1.0 with (p < 0.001). There was no statistically significant the correlation between ablation arc and reduction in IOP (p=0.50) or final IOP (p=0.89).
Our results indicate that the amount of TM and SC tissue ablated does not significantly alter the post-operative IOP result. One possible explanation is that if at least partially circumferential flow in SC exists, then the size of the opening would be less important than the maintenance of a patent opening in the TM and SC. An alternate explanation is that the size of the ablation arcs fell in a relatively narrow range in our patients. Clarification of this issue may require comparison of one-site vs two-site surgeries with a larger range of ablation arcs.
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