Canaloplasty an option after failed trabeculectomy

A perfectly performed trabeculectomy can fail to lower intraocular pressure (IOP), even if mitomycin C has been used, because of pre-existing conjunctival scarring. If this is the case, a second trabeculectomy will seldom provide adequate IOP control for precisely the same reasons that caused the initial surgical failure. Typically, either the implant of a tube or a diode laser cyclophotocoagulation would be recommended as the next step for treating these cases, but both of these options entail several possible serious complications. Therefore, an alternative surgical option for treating glaucoma is essential.

Although it is normally indicated for eyes that have not undergone previous filtrating surgery for glaucoma, canaloplasty is a viable alternative surgical option for a select number of eyes in which postoperative gonioscopic examination shows that the initial 'trabeculectomy' had been performed anterior to the trabecular structures - in other words, had in fact been a sclero-keratectomy - and that Schlemm's canal had been left intact. This scenario is now seen more frequently, especially in eyes in which an emport-piece trabeculectomy is associated with a one-site phacoemulsification.

As canaloplasty is not dependent on conjunctiva status for proper functioning, it is an appropriate treatment in these eyes, particularly in cases where IOP remains elevated despite maximum tolerated medical therapy and therefore further surgery is indicated.

"A mandatory prerequisite for this surgery is an apparently intact Schlemm's canal at gonioscopy," he notes. "The presence of peripheral anterior synechiae or previous argon laser trabeculoplasty can affect the success of canaloplasty, making it difficult or sometimes impossible to perform cannulation; however, these should not be considered as absolute contraindications for this procedure."