Canaloplasty is a non-penetrating surgical technique for glaucoma which aims to restore the natural drainage of fluid from the eye.
Canaloplasty may be performed under local or general anaesthetic. A superficial hinged flap of sclera is made and a deeper flap excised, exposing Schlemm’s canal. A microcatheter with an illuminated tip is introduced into the canal and advanced around its entire circumference. As the catheter tip advances, viscoelastic fluid is injected into the canal to dilate it. After catheterisation of the entire canal length is complete, a suture is tied to the tip of the microcatheter, which is withdrawn, pulling the suture into the canal. The
suture is cut from the microcatheter and tied in a loop encircling the inner wall of the canal. The suture is tightened, so distending the trabecular meshwork with the aim of widening the canal.
The superficial flap is sutured. A special ultrasound imaging system is used to help identify the canal and to visualise the instruments in the canal before, during and after the surgery.
Efficacy
In a case series of 94 patients, successful circumferential catheterisation of Schlemm’s canal was achieved in 88% (83/94) of patients, and a suture was successfully placed in the canal in 79% (74/94) of patients. Mean intraocular
pressure was reduced from 24.7 mmHg at baseline to 15.3 mmHg at 12-month follow-up (p < 0.05). (The normal upper limit for intraocular pressure is 21 mmHg.) The mean number of drugs to lower the intraocular pressure was reduced from 1.9 at baseline to 0.6 at 12-month follow-up.
Furthermore, 88% (50/57) and 96% (46/48) of patients with successful suture placement had intraocular pressures of 21 mmHg or lower after 3 months and 6 months, respectively (with or without drugs to lower intraocular pressure).Four patients had poor intraocular pressure control after canaloplasty and required subsequent trabeculectomy.
The Specialist Advisers considered key efficacy outcomes to include control of intraocular pressure, preservation of the visual field and ocular comfort.
Safety
The case series of 94 patients reported ocular-related complications including hyphema (the presence of blood in the anterior chamber) (3%), elevated intraocular pressure (3%), detachment of Descemet’s membrane (1%), hypotony (abnormally low intraocular pressure) (1%), choroidal effusion (1%) and exposed closure suture (1%) (absolute figures not reported).
In the same case series, the loss of two or more lines of best corrected visual acuity was reported in 25% (18/71) of patients at 1-month follow-up, 7% (5/68) of patients at 3-month follow-up and 9% (4/47) of patients at 12-month follow-up. The authors noted that the decline in visual acuity in these patients was related to disease processes not associated with the canaloplasty procedure.
The Specialist Advisers considered theoretical adverse events to include anterior chamber perforation, tearing of Descemet’s membrane resulting in corneal opacification or retinal damage, intraocular inflammation caused by the suture, cataract formation, sustained increases in intraocular pressure, hypotony, and bleb formation or suture exposure with endophthalmitis.
