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Editors Selection IGR 11-2

Surgical Treatment: Canaloplasty

Comment by Shlomo Melamed on:

23834 Canaloplasty: circumferential viscodilation and tensioning of Schlemm canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults: two-year interim clinical study results, Lewis RA; von Wolff K; Tetz M et al., Journal of Cataract and Refractive Surgery, 2009; 35: 814-824

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In recent years, various new methodologies for glaucoma surgery have evolved. The common denominator for most of these procedures is the attempt to lower IOP by using a less invasive approach and without the formation of a filtration bleb ( which may be associated with too many complications). Surgery of Schlemm's canal is certainly one of these approaches, with quite a few novel technologies already in use: Non-penetrating deep Sclerectomy (NPDS) , viscocanalostomy, Trabeculotomy, Trabectome, Stents into Schlemm's canal and Canaloplasty.

In this manuscript, Lewis et al. (892) report on the results of canaloplasty in 127 eyes with a follow-up of 24 months. Their results show IOP reduction of from 23.6 mmHg to 16 mmHg for all patients. However, when analyzing the data for canaloplasty alone versus combined cataract extraction with canaloplasty ‐ there seems to be a better effect on IOP in the latter group (postoperative IOP of 13.4 mmHg in the combined operation group versus 16.3 mmHg in the canaloplasty-only group).
The hypotensive effect of canaloplasty is apparently enhanced by phacoemulcification in the combined group, and this adds to other reports claiming IOP reduction by phacoemulcification only. But, canaloplasty is certainly effective on its own, with stable reduction of IOP to the mid-teens when performed as a single procedure. The mechanism of IOP reduction in canaloplasty is still not fully understood. It is believed that distention of Schlemm's canal, disruption of the inner wall and stretching of trabecular beams are associated with the increased outflow facility reported in these cases. It is interesting that, although 30% of the resistance to aqueous flow beyond Schlemm's canal is not affected in this procedure, IOP is still effectively reduced.

Canalolpasty seems to be a very safe procedure, as it is less invasive than trabeculectomy. One of the problems is the long learning curve and surgery time needed. More experience with this technology and other less invasive procedures is needed before any of them is declared the better approach.

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