Suture Distension of Schlemm's Canal in Canaloplasty: An Anterior Segment Imaging Study

Ab-externo canaloplasty with and without suture in highly myopic eyes

PURPOSE

To evaluate the effectiveness of ab-externo canaloplasty using the iTrack canaloplasty microcatheter (Nova Eye Inc, Fremont, California), with or without suture, in glaucoma patients with high myopia.

METHODS

This was a prospective, single-center, single-surgeon, observational study comparing the outcomes of ab-externo canaloplasty performed with a tensioning suture (suture group) and without a tensioning suture (no-suture group) in mild to severe glaucoma patients with high myopia. Twenty-three eyes received canaloplasty as a standalone procedure, 5 in combination with phacoemulsification. Primary efficacy endpoints included intraocular pressure (IOP) and the number of glaucoma medications. Safety was assessed based on reported complications and adverse events.

RESULTS

Twenty-nine eyes of 29 patients with a mean age of 61.2 ± 12.3 years; 19 eyes in the no-suture group and 10 eyes in the suture group. All eyes demonstrated a significant reduction in IOP 24 months postoperatively, from 21.9 ± 7.22 to 15.4 ± 4.86 mmHg in the suture group and from 23.8 ± 7.58 to 19.7 ± 3.68 mmHg in the no-suture group. The mean number of anti-glaucoma medications reduced from 3.1 ± 0.6 to 0.4 ± 0.7 in the suture group and 3.3 ± 0.9 to and 0.2 ± 0.6 in the no-suture group at 24 months. IOP was not significantly different at baseline between the 2 groups, but it was statistically different at 12 and 24 months. There was no statistically significant difference in the number of medications between the groups at baseline, 12 and 24 months. No serious complications were reported.

CONCLUSION

Ab-externo canaloplasty performed either with or without a tensioning suture demonstrated good effectiveness in highly myopic eyes with a significant reduction in IOP and number of anti-glaucoma medications. The suture group achieved a lower postoperative IOP. However, the no-suture modification provides a similar reduction in medications with reduced tissue handling.

Access to Schlemm's canal for canaloplasty: an intra-individual comparison of two dissection techniques

PURPOSE

To compare a modified incision technique with classic scleral flap dissection for canaloplasty with canal expander regarding efficacy and safety.

METHODS

In a prospective randomized pilot study of 32 eyes of 16 patients with primary open-angle glaucoma, access to Schlemm's canal was created by deep lamellar dissection (scleral flap excision, group 1) or by vertical cut-down incision (group 2). Following canal opening and viscodilation with microcannula and sodium hyaluronate, two Stegmann Canal Expanders were implanted, and the scleral flap or vertical incision, respectively, was closed watertight.

RESULTS

Mean preoperative intraocular pressure (IOP) was 34.9 mmHg ± 6.7 [standard deviation (SD)] in group 1 and 33.8 mmHg ± 7.7 (SD) in group 2 (p = 0.66); mean postoperative IOP without medications was 14.3 mmHg ± 2.9 (SD) in group 1 and 14.8 mmHg ± 5.2 (SD) in group 2 at 1 month (p = 0.76), and 14.4 mmHg ± 1.9 (SD) in group 1 and 16.8 mmHg ± 3.1 (SD) in group 2 at 12 months (p = 0.01). Overall, there was a significant preoperative-postoperative IOP difference between groups (19.4 mmHg ± 10.1, group 1; 16.6 mmHg ± 8.9, group 2; p = 0.02). Surgery type had a significant effect when adjusted for preoperative IOP, cup-disc ratio, eye side, follow-up number and surgery type (p < 0.01, anova). No filtering bleb was observed in either group. Intra- and postoperative complications were rare and included peripheral Descemet's membrane detachment (3), microhyphema (2) and cannulation into the anterior chamber (1).

CONCLUSIONS

In this intra-individual comparative study of ab externo canaloplasty with the canal expander, IOP reduction was substantial in both groups and slightly greater in the group with deep scleral flap excision. Additional IOP reduction by transscleral drainage through the Descemet's membrane window and intrascleral lake is suggested.

Canaloplasty in the Treatment of Primary Open-Angle Glaucoma: Patient Selection and Perspectives

Canaloplasty is a surgical procedure that has undergone a number of developments since its introduction in 2005. Many thousands of canaloplasties have been performed around the world since then and is, by definition, a blebless procedure. It does not necessitate the use of any antifibrotic agents and results in safe and effective IOP reductions in patients with open-angle glaucoma (OAG) with minimal complications and no bleb-related adverse events. When considering the surgical management of patients with early and medium stages of the disease, canaloplasty can be considered as a first line option. This paper will overview the theoretical effectiveness of canal surgery, the fundamental aspects of aqueous outflow resistance with particular emphasis on the role of the trabecular meshwork, Schlemm's canal, and the collector channels, and the methods available for the clinical evaluation of the outflow pathways in relation to the ocular anatomy. Further, the paper will detail the surgical technique itself and how this has developed over time together with the clinical aspects that should be accounted for when selecting patients for this surgery.

Outcomes of 360° suture trabeculotomy after unsuccessful canaloplasty

BACKGROUND

Canaloplasty is a well-established non-penetrating glaucoma surgery. Unsuccessful outcomes can be enhanced by micro-invasive 360° suture trabeculotomy (360°trabeculotomy), analyzed in this study.

METHODS

This retrospective study included twenty eyes of 19 patients, mean age 59.7±17.2 years, with primary open-angle glaucoma (POWG n = 14), pseudoexfoliation glaucoma (PEX n = 3), juvenile glaucoma (n = 2) and aphakic glaucoma (n = 1), who underwent micro-invasive 360° trabeculotomy after unsuccessful (intraocular pressure (IOP) >21 mmHg under maximum glaucoma eye drop therapy (Meds)) canaloplasty. IOPs, Meds, complications and failure rates (IOP >21 mmHg at two consecutive follow-ups) were evaluated. Complete success (no Meds) and qualified success (with Meds) rates for IOP levels ≤21 mmHg and ≤ 18 mmHg at the last follow-up were evaluated.

RESULTS

IOPs and Meds were significantly reduced from before to 1 week (10.3±3.1 days) after 360° trabeculotomy (IOP, 28.3±6.0 mmHg to 15.8±4.5 mmHg; p < 0.001; Meds, 3.1 ± 1.2 to 1.0 ± 1.2; p < 0.001). IOPs (p = 0.37) and Meds (p = 0.33) did not decrease further from 1 week until the last follow-up (18.3 ± 8.2 months (IOP, 14.4±3.8 mmHg; Meds, 1.5±1.3)). Complete and qualified success was 25% (5/20) and 70% (14/20) for IOP ≤21 mmHg, as well as 25% (5/20) and 60% (12/20) for IOP ≤18 mmHg. Four eyes had postoperative hyphema, which resolved after a mean period of 4.0 ± 2.2 days. Five failures occurred after a mean of 40.6 ± 51.9 days after 360° trabeculotomy. All failures underwent trabeculectomy. Eyes that needed early (≤3 months post canaloplasty) 360° trabeculotomy showed higher IOPs before (p < 0.001) and lower (p = 0.03) IOPs 2 months post 360° trabeculotomy than eyes with late (>3 months) 360° trabeculotomy surgery.

CONCLUSIONS

360° trabeculotomy is a safe, micro-invasive, simple and successful method to enhance failed canaloplasty.

Changes in spectral parameters of corneal pulse following canaloplasty

PURPOSE

To ascertain whether changes in the spectral content of the corneal pulse (CP) signal, measured in vivo in primary open-angle glaucoma (POAG) patients, indirectly reflect changes in corneal biomechanics after canaloplasty.

METHODS

Fifteen eyes of 15 POAG patients who underwent canaloplasty combined with phacoemulsification were enrolled. Standard ophthalmic examinations were conducted before washout, pre-operatively, at days 1, 7, and 1, 3, 6, and 12 months after surgery. Non-contact measurements of the CP signal were performed at pre-washout, pre-operatively, and at 3, 6, and 12 months post-operatively. Then, amplitudes of the CP first five harmonics associated with the heart rate were estimated. Temporal changes of all considered parameters were tested at a Bonferroni-adjusted significance level set to 0.005.

RESULTS

A decrease in the amplitude of the first harmonic and an increase in the normalized amplitude of the third harmonic (A_CP3n) of the CP signal were noticed between the pre-washout and the pre-operative stages (p = 0.003 and p = 0.004, respectively). This corresponds to an increase in median intraocular pressure (IOP) values by 6.0 mmHg (p = 0.0045). After surgery, A_CP3n reached the highest value at 3 months post-operatively, compared with pre-washout level (p = 0.0045).

CONCLUSIONS

Alterations in corneoscleral stiffness caused by surgery are reflected in changes in the A_CP3n value. Hence, post-operative corneal biomechanics could be monitored indirectly by this supporting indicator that can be used to estimate the time at which measures of IOP are no longer biased by the changed cornea boundary conditions caused by canaloplasty.

CLINICAL TRIALS REGISTRATION

NCT02908633.

Circumferential viscodilation of Schlemm's canal for open-angle glaucoma: ab-interno vs ab-externo canaloplasty with tensioning suture

Purpose

To compare the efficacy of minimally invasive ab-interno canaloplasty (ABiC) vs ab-externo canaloplasty (CP) in reducing intraocular pressure (IOP) and glaucoma medication dependence.

Patients and methods

This nonrandomized, retrospective, single-center, paired eye study assessed the 12-month outcomes of 12 patients with primary open-angle glaucoma who underwent ABiC in one eye and CP in the other eye, either as stand-alone procedures or combined with cataract extraction. Primary endpoints included mean IOP and number of glaucoma medications at 12 months postoperative. Secondary endpoints included surgical complications and secondary interventions.

Results

Four males and eight females with a mean age of 73.8±12.6 years were included. In the CP group, the mean preoperative IOP was 18.1±3.9 mmHg on 2.4±0.5 medications, which reduced to 13.5±2.2 mmHg (P<0.05) on 0.9±0.9 medications (P<0.001). In the ABiC group, the mean preoperative IOP was 18.5±3.4 mmHg on 2.4±0.5 medications and postoperative IOP was 13.8±2.2 mmHg (P<0.05) on 0.8±0.8 medications (P<0.05). There was no significant difference in IOP and medication use between treatment groups at 12 months postoperative. No serious adverse events were recorded in either group, though two patients in the CP group developed pressure spikes 10 mmHg beyond preoperative IOP.

Conclusion

This paired eye study found ABiC to have comparable IOP lowering and glaucoma medication reduction to CP in open-angle glaucoma. This suggests ABiC may be a suitable method for improving aqueous outflow via the trabecular pathway. Further large-scale investigation is needed.

Canaloplasty with Stegmann Canal Expander for primary open-angle glaucoma: two-year clinical results

PURPOSE

To examine longer-term postsurgical safety and efficacy of a new expander for Schlemm's canal.

METHODS

In a non-comparative, prospective study, 42 White patients with medically uncontrolled primary open-angle glaucoma (POAG) underwent primary canaloplasty with >2-year follow-up. The bleb-independent procedure comprised catheter-assisted canaloplasty and implantation of two Stegmann Canal Expanders to maintain trabecular distension and canal patency over 180°. Intraocular pressure (IOP), glaucoma medication use and complications were assessed.

RESULTS

Mean IOP was 26.8 ± 5.6 mmHg presurgery, 12.8 ± 1.5 mmHg at 6 months, 13.2 ± 1.2 mmHg at 12 months and 13.3 ± 2.5 mmHg at 24 months (p < 0.001). Rate of complete success, defined as IOP ≤21, ≤18 and ≤16 mmHg and a ≥ 30% IOP reduction, was 85% (95% CI: 0.76-0.95), 85% (0.76-0.95) and 82% (0.70-0.96) at 12 months and 83% (0.73-0.94), 80% (0.70-0.92) and 80% (0.70-0.92) at 24 months. Preoperative factors were not significant predictors of ≤16 mmHg IOP reduction: IOP (hazard ratio [HR]: 0.68; 95% CI: 0.44-1.04; p = 0.08), mean visual defect (1.06; 0.90-1.20; p = 0.47), number of medications (0.59; 0.17-2.14; p = 0.42) and age (0.96; 0.87-1.13; p = 0.41). Number of medications dropped from 2.8 ± 0.4 presurgery to 0.2 ± 0.5 postsurgery (p < 0.001). Mean preoperative best-corrected visual acuity was 0.19 ± SD 0.21 (range: 0-1.6), and logMAR was similar to 0.23 ± 0.16 (range: 0-1.6; p = 0.42) after a mean follow-up of 27.4 months. Complications included peripheral Descemet's membrane detachment (7.2%) and trimming of the expander (4.7%) during surgery, and transient microhyphaema (23.8%) and IOP elevation (7.2%) postsurgery.

CONCLUSION

Canaloplasty with the Stegmann Canal Expander was a safe and effective procedure to reduce IOP in White patients with moderate to advanced POAG.

A System Review and Meta-Analysis of Canaloplasty Outcomes in Glaucoma Treatment in Comparison with Trabeculectomy

Purpose. This system review studied the efficiency and safety of canaloplasty (CP) and compared the outcomes between CP and trabeculectomy (TE). Methods. Literatures were searched in PubMed and EMBASE. The meta-analysis was conducted on the postoperative outcomes in CP and then on the differences of outcomes between CP and TE. Results. In the meta-analysis, IOP decreased by 9.94 (95% CI 8.42 to 11.45) mmHg with an average AGM reduction of 2.11 (95% CI 1.80 to 2.42) one year after CP. The IOP reduction was significantly higher after TE than after CP, with an average difference of 3.61 (95% CI 1.69 to 5.53) mmHg at 12 months postoperationally. For complications, the incidence of hyphema was significantly higher in CP and the Descemet membrane detachment was just reported in CP, with an incidence of 3%. However, the incidence was significantly lower in CP of hypotony and of choroidal effusion/detachment. Meanwhile, suprachoroidal hemorrhage and bleb needling were only reported in TE. Conclusions. CP was less effective in IOP reduction than TE, but CP was able to achieve similar postoperative success rates and reduce the number of AGMs likewise. CP was also associated with lower incidence of complications. More high-quality researches are needed in the future to verify our findings in this system review.

Canaloplasty: Current Value in the Management of Glaucoma

Canaloplasty is a nonpenetrating blebless surgical technique for open-angle glaucoma, in which a flexible microcatheter is inserted within Schlemm's canal for the entire 360 degrees. When the microcatheter exits the opposite end, a 10-0 prolene suture is tied and it is then withdrawn, by pulling microcatheter back through the canal in the opposite direction. Ligation of prolene suture provides tension on the canal and facilitates aqueous outflow. The main advantage of canaloplasty is that this technique avoids the major complications of fistulating surgery related to blebs and hypotony. Currently, canaloplasty is performed in glaucoma patients with early to moderate disease and combination with cataract surgery is a suitable option in patients with clinically significant lens opacities.