Canaloplasty for open angle glaucoma: a three years critical evaluation and comparison with viscocanalostomy

OBJECTIVE: Patients undergoing primary Canaloplasty for open angle glaucoma, under the care of the two authors, were entered into a common data base. The two authors also pooled their results at three years, from a prospective audit of patients undergoing Viscocanalostomy, from the same sites, in order to provide a comparison of the successes and complications of the two procedures. PATIENTS AND METHODS: Surgery was carried at: Warrington Hospital, Warrington, UK; Spire Cheshire Hospital, Stretton, UK; Augencentrum Porz, Cologne, Germany and University Eye Hospital Padua, Italy, between May 1997 and May 2008. Ninety seven eyes of 75 patients underwent Canaloplasty with a mean age of 67 years (range 41 to 85 years) and a mean follow up of 19 months (range 6 months to 3 years). One hundred and twenty eyes of 92 patients had undergone Viscocanalostomy with a mean age of 68 years (range 26 to 92 years) and a mean follow up of 22 months (range: 3 months to 3 years). RESULTS: There were no statistically significant differences in the mean pre-operative IOP and number of medications between groups. Both Canaloplasty and Viscocanalostomy groups showed a statistically significant reduction in IOP (t = 19.25. p < 0.05 and 15.54. p < 0.05 respectively) and number of medications (t = 21.18 p < 0.05 and 23.04 p < 0.05 respectively) from pre-operative levels. There was a statistically significant difference in favour of the Canaloplasty group in post-operative reduction of both IOP and number of medications compared with the Viscocanalostomy group (Mann-Whitney U 3940.5 and 4109.5 p = < .001 respectively). Of the 97 eyes that underwent Canaloplasty, using the criteria of success as ≤ 21 mm Hg, a success rate of 97% with medication and 92% with no medication was achieved. When success is defined at ≤ 17 mm Hg, the success rate was 87% with medication and 83% with no medication. For the 120 eyes undergoing Viscocanalostomy, using the criteria of success as ≤ 21 mm Hg, a success rate of 96% on medication and 55% with no medication was achieved. However, when success is defined at ≤ 17 mm Hg the success rate drops to 68% on medication and 42% with no medication. There was a statistically significant difference between groups in favour of the Canaloplasty group in the number of patients achieving a post-operative IOP of 17mm Hg or less (t = 2.55 p = .001). CONCLUSIONS: The results reported here show that both Viscocanalostomy and Canaloplasty are safe and effective surgical procedures for the management of Primary Open Angle Glaucoma with fewer complications than the current literature states for trabeculectomy. Moreover, when the results of these two groups of similar patients are compared, Canaloplasty produced significantly better results than Viscocanalostomy.