Dilation of Schlemm's Canal during Glaucoma Surgery

We compared surgical outcomes in patients with either primary open-angle glaucoma or exfoliation glaucoma after undergoing combined phacoemulsification with either a 120° or 180° incision during a Schlemm’s canal microhook ab interno trabeculotomy (μLOT-Phaco). This retrospective comparative case series examined 52 μLOT-Phaco eyes that underwent surgery between September 2017 and December 2020. Surgical qualified success was defined as an intraocular pressure (IOP) of ≤20 mmHg, ≥20% IOP reduction with IOP-lowering medications, and no additional glaucoma surgery. Success rates were evaluated by Kaplan-Meier survival analysis. The number of postoperative IOP-lowering medications and occurrence of complications were also assessed. Mean preoperative IOP in the 120° group was 16.9 ± 7.6 mmHg, which significantly decreased to 10.9 ± 2.7 mmHg (p < 0.01) and 11.1 ± 3.1 mmHg (p = 0.01) at 12 and 24 months, respectively. The mean number of preoperative IOP-lowering medications significantly decreased from 2.8 ± 1.4 to 1.4 ± 1.4 (p < 0.01) at 24 months. Mean preoperative IOP in the 180° group was 17.1 ± 7.0 mmHg, which significantly decreased to 12.1 ± 3.2 mmHg (p = 0.02) and 12.9 ± 1.4 mmHg (p = 0.01) at 12 and 24 months, respectively. The mean number of preoperative IOP-lowering medications significantly decreased from 2.9 ± 1.2 to 1.4 ± 1.5 (p < 0.01) at 24 months. The probability of qualified success at 24 months in the 120° and 180° groups was 50.4% and 54.6%, respectively (p = 0.58). There was no difference observed for hyphema formation or IOP spikes. Surgical outcomes were not significantly different between the 120° and 180° incisions in Schlemm’s canal.

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Complications Common to Nonpenetrating Surgeries

Complications of Glaucoma Surgery ◽

10.1093/oso/9780195382365.003.0079 ◽

2013 ◽

Author(s):

Andrew C. Crichton

Keyword(s):

Glaucoma Surgery ◽

Outer Wall ◽

Glaucoma Drainage Device ◽

Deep Sclerectomy ◽

Success Rates ◽

Schlemm’S Canal ◽

Schlemm's Canal ◽

Descemet's Membrane ◽

Descemet’S Membrane ◽

Controlled Flow

Nonpenetrating glaucoma surgery encompasses techniques that involve a deep dissection to the level of Descemet’s membrane, allowing aqueous seepage. The major techniques covered by the term “nonpenetrating surgery” are deep sclerectomy with or without implant and viscocanalostomy. In large meta-analyses comparing nonpenetrating procedures to trabeculectomy, trabeculectomy resulted in lower intraocular pressures (IOP) but a higher risk of postoperative complications. Although nonpenetrating surgery is successful in lowering IOP, the amount of IOP lowering is typically not as low as can be achieved with trabeculectomy. Consequently, patient selection with regard to the target IOP is important in the decision of whether or not to perform a nonpenetrating procedure. The goal of nonpenetrating procedures is to lower IOP with fewer complications than are seen with trabeculectomy. The complications that can occur can be easily understood and predicted by an understanding of the techniques and modifications, as well as knowledge and mechanisms of the adjustments that can be used postoperatively to enhance success. After appropriate anesthetic, the techniques involve a deep dissection in the sclera to the limbus. In the case of deep sclerectomy, after the initial half-thickness flap is fashioned, a second deeper flap is created and excised. This dissection is taken to the level of Descemet’s membrane, allowing controlled flow of aqueous. A fine forceps may be used to strip the outer wall of Schlemm’s canal, further enhancing the flow. The space created by the excision can then be filled with an implant, such as collagen (AquaFlow™ Collagen Glaucoma Drainage Device; STAAR® Surgical Company, Monrovia, California) or hyaluronate (SK Gel®; Corneal Laboratories, Paris, France). For viscocanalostomy, Schlemm’s canal is identified and dilated by using viscoelastic. With deep sclerectomy, intraoperative or postoperative antimetabolites may be used to try to increase success rates by limiting the inflammatory response. Goniopuncture to the Descemet’s window is often required postoperatively (in up to 67% of cases) to enhance flow and lower IOP. The available evidence on complications of nonpenetrating glaucoma surgery is relatively sparse and may be challenging to interpret. Comparative studies between trabeculectomy and nonpenetrating surgery would seem to show fewer complications in the nonpenetrating group.

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Viscocanalostomy: A Pilot Study

European Journal of Ophthalmology ◽

10.1177/112067219800800201 ◽

1998 ◽

Vol 8 (2) ◽

pp. 57-61 ◽

Cited By ~ 52

Author(s):

R.G. Carassa ◽

P. Bettin ◽

M. Fiori ◽

R. Brancato

Keyword(s):

Intraoperative Complications ◽

Glaucoma Surgery ◽

Ophthalmological Examination ◽

Schlemm’S Canal ◽

Short Term ◽

Term Study ◽

Schlemm's Canal ◽

Short Term Study ◽

A Prospective Study

Purpose Viscocanalostomy is a new, non-penetrating procedure for glaucoma surgery. We started a prospective study to assess the effectiveness and safety of the operation. Materials and methods Up to March 1998 we enrolled 33 patients (33 eyes) suffering from glaucoma, uncontrolled despite maximum medical therapy, who underwent viscocanalostomy according to Stegmann's technique. A complete ophthalmological examination was performed the day before surgery and on days 1 and 7 postoperatively. Further visits were scheduled at months 1, 3, 6 and 12. Results In four eyes Schlemm's canal was either missed or not deroofed properly, and the procedure was converted into simple trabeculectomy. After a mean follow-up of 3.0±2.6 months (range 1–10), success defined as IOP > 2 and < 21 mmHg with no medication was obtained in 86.2% of the cases (25/29); 23 out of 29 eyes (79.3%) had IOP > 2 and < 16 mmHg. In the 25 successful eyes, mean IOP was 27.7±9.5 mmHg (range 13–48) preoperatively and 12.0±3.0 mmHg (range 7–18) (p<0.0001) at the end of the follow-up period. Mean VA ranged from 0.35±0.34 to 0.32±0.32 (n.s.). Intraoperative complications included Descemet rupture (7), with iris plugging in two cases; choroidal deroofing (3), irregular incision of Schlemm's canal (2). Postoperative complications included: self-resolving 2-mm hyphema (4); IOP spike (1); inadvertent filtering bleb (2); hypotony with choroidal detachment for one week (1). Conclusions In this short-term study, viscocanalostomy proved effective and safe in lowering IOP in glaucomatous eyes.

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Angle and Nonpenetrating Glaucoma Surgery

Complications of Glaucoma Surgery ◽

10.1093/oso/9780195382365.003.0011 ◽

2013 ◽

Author(s):

Huijuan Wu ◽

Teresa C. Chen

Keyword(s):

Endothelial Cells ◽

Anterior Chamber ◽

Trabecular Meshwork ◽

Glaucoma Surgery ◽

Anterior Chamber Angle ◽

Schlemm’S Canal ◽

Schlemm's Canal ◽

Outflow Pathway ◽

Aqueous Outflow ◽

Chamber Angle

The outflow of aqueous via the anterior chamber angle is a constant process. The aqueous is formed by the ciliary processes and then passes through the pupil from the posterior chamber to the anterior chamber (Figure 2.1). About 83%–96% of the aqueous finally exits the eye into the anterior chamber angle via the trabecular meshwork—Schlemm’s canal—venous system (i.e., the conventional or canalicular outflow pathway). The other 5%–15% of aqueous outflow occurs via uveoscleral outflow (i.e., the unconventional or extracanalicular outflow pathway), with aqueous passing through the ciliary muscle and iris, then entering into the supraciliary and suprachoroidal spaces, and then finally exiting the eye through the sclera or along the penetrating nerves and vessels. Glaucoma is usually associated with aqueous outflow problems through a variety of mechanisms. For the developmental glaucomas, the improper development of the outflow structures is the main reason for high eye pressures. In the primary and secondary open-angle glaucomas, the theories to explain the diminished outflow facility are numerous. Possible etiologies are as follows: deposition of foreign material (such as pigment, red blood cells, glycosaminoglycans, extracellular lysosomes, plaque-like material, and proteins) into the trabecular meshwork (TM) and the wall of Schlemm’s canal (SC), loss of trabecular endothelial cells, structural changes of the inner wall of SC, and abnormal phagocytic activity of trabecular endothelial cells. In angle closure glaucoma, the peripheral iris closes the entrance to the TM by the anterior pulling mechanism or the posterior pushing mechanism, resulting in the direct blockage of conventional outflow. The goal of angle and nonpenetrating procedures is to restore aqueous outflow, thereby lowering intraocular pressure (IOP). Angle surgery restores outflow by re-opening the natural channels for aqueous outflow, and nonpenetrating glaucoma surgery creates an artificial external filtration site and partly restores the normal physiologic pathways. In 1936, Otto Barkan was the first to describe a surgical procedure that creates an internal incision into trabecular tissue under direct magnified view of the anterior chamber angle.

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Canaloplasty with mitomycin C after previous combined cataract surgery and Schlemm’s canal microstent implantation

European Journal of Ophthalmology ◽

10.1177/11206721211000275 ◽

2021 ◽

pp. 112067212110002

Author(s):

Eva Elksne ◽

Karl Mercieca ◽

Verena Prokosch-Willing

Keyword(s):

Cataract Surgery ◽

Mitomycin C ◽

Primary Open Angle Glaucoma ◽

Open Angle Glaucoma ◽

Glaucoma Surgery ◽

Glaucomatous Optic Neuropathy ◽

Schlemm’S Canal ◽

Schlemm's Canal ◽

The Right

We report on a 56-year-old male with primary open-angle glaucoma who underwent mitomycin C augmented canaloplasty enabling filtration in the right eye after cataract surgery combined with a Schlemm’s canal microstent 3 years previously. He showed progressive glaucomatous optic neuropathy and was highly myopic (axial length 32.05 mm, spherical equivalent −18.75 dioptres in the right eye). Augmented canaloplasty was performed uneventfully and 360° catheterisation was achieved followed by the placement of a 10-0 polypropylene suture in Schlemm’s canal. Intraocular pressure (IOP) in the first post-operative day was reduced from 19 to 6 mmHg. At 1-month follow-up IOP was 12 mmHg off glaucoma medications. The presence of a minimally invasive glaucoma surgery (MIGS) device did not hinder successful catheterisation of Schlemm’s canal. Significant reduction of IOP was obtained in the early post-surgical period. No intra-operative complications were registered and only transient hyphema in early post-operative period was reported. This augmented canaloplasty could be an effective alternative to trabeculectomy even after Schlemm’s canal microstent implantation.

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360° Ab-Interno Schlemm’s Canal Viscodilation with OMNI Viscosurgical Systems for Open-Angle Glaucoma—Midterm Results

Journal of Clinical Medicine ◽

10.3390/jcm11010259 ◽

2022 ◽

Vol 11 (1) ◽

pp. 259

Author(s):

Giacomo Toneatto ◽

Marco Zeppieri ◽

Veronica Papa ◽

Laura Rizzi ◽

Carlo Salati ◽

...

Keyword(s):

Surgical Procedures ◽

Open Angle Glaucoma ◽

Cataract Extraction ◽

Glaucoma Surgery ◽

Open Angle ◽

Schlemm’S Canal ◽

Schlemm's Canal ◽

Primary Success ◽

Group 2 ◽

Ab Interno

Purpose: To evaluate the effectiveness of ab-interno microcatheterization and 360° viscodilation of Schlemm’s canal (SC) performed with OMNI viscosurgical system in open angle glaucoma (OAG) together or not with phacoemulsification. Setting: Two surgical sites. Design: Retrospective, observational. Methods: Eighty eyes from 73 patients with mild to moderate OAG underwent ab- interno SC viscodilation performed with OMNI system. Fifty eyes (Group 1) underwent only SC viscodilation, while 30 eyes (Group 2) underwent glaucoma surgery + cataract extraction. Primary success endpoint at 12 months was an intraocular pressure (IOP) reduction higher than 25% from baseline with an absolute value of 18 mmHg or lower, either on the same number or fewer ocular hypotensive medications, without further interventions. Secondary effectiveness endpoints included mean IOP, number of medications and comparison of outcomes between groups. Safety endpoints consisted of best-corrected visual acuity (BCVA), adverse events (AEs), and subsequent surgical procedures. Results: Primary success was achieved in 40.0% and 67.9% in Groups 1 and 2, respectively. Mean IOP at 12-month follow-up showed a significant reduction in both groups (from 23.0 to 15.6 mmHg, p < 0.001, and from 21.5 to 14.1, p < 0.001, in Groups 1 and 2, respectively). Mean medication number decreased in both groups (from 3.0 to 2.0, p < 0.001 and from 3.4 to 1.9, p < 0.001, in Groups 1 and 2, respectively). AEs included hyphema (2 eyes), mild hypotony (4 eyes), IOP spikes one month after surgery (1 eye). Twelve eyes (15.0%) required subsequent surgical procedures. No BCVA reduction was observed. Conclusions: Viscodilation of SC using OMNI viscosurgical systems is safe and relatively effective in reducing IOP in adult patients with OAG.

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Effects of Schlemm’s Canal Expansion: Biomechanics and MIGS Implications

Life ◽

10.3390/life11020176 ◽

2021 ◽

Vol 11 (2) ◽

pp. 176

Author(s):

Chen Xin ◽

Shaozhen Song ◽

Ningli Wang ◽

Ruikang Wang ◽

Murray Johnstone

Keyword(s):

Three Dimensional ◽

Glaucoma Surgery ◽

Pressure Control ◽

Biomechanical Properties ◽

Schlemm’S Canal ◽

Fluid Bolus ◽

Cross Sectional ◽

Schlemm's Canal ◽

Anterior Segments ◽

The Right

Objective: To evaluate the change of biomechanical properties of the trabecular meshwork (TM) and configuration of collector channels (CC) by high-resolution optical coherence tomography (HR-OCT) induced by Schlemm’s canal (SC) dilation. Methods: The anterior segments of two human eyes were divided into four quadrants. One end of a specially designed cannula was placed in SC and the other end connected to a perfusion reservoir. HR-OCT provided three-dimensional (3D) volumetric and two-dimensional (2D) cross-sectional imaging permitting assessment of the biomechanical properties of the TM. A large fluid bolus was introduced into SC. Same-sample, pre and post deformation and disruption of SC and CC lumen areas were analyzed. Results: Morphologic 3D reconstructions documented pressure-dependent changes in lumen dimension of SC, CC, and circumferential intrascleral channels. 2D imaging established volumetric stress-strain curves (elastance curves) of the TM in quadrants. The curves of TM elastance shift to the right with an increase in pressure-dependent steady-state SC area. After a bolus disruption, the SC area increased, while the CC area decreased. Conclusion: Our experimental setup permits the study of the biomechanical properties of TM by examining elastance, which differs segmentally and is altered by mechanical expansion of SC by a fluid bolus. The study may shed light on mechanisms of intraocular pressure control of some glaucoma surgery.

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Advanced Glaucoma Surgery with a Focus on Schlemm’s Canal

European Ophthalmic Review ◽

10.17925/eor.2009.03.02.40 ◽

2009 ◽

Vol 03 (02) ◽

pp. 40 ◽

Cited By ~ 1

Author(s):

Matthias C Grieshaber ◽

Keyword(s):

Open Angle Glaucoma ◽

Venous Pressure ◽

Glaucoma Surgery ◽

Schlemm’S Canal ◽

Schlemm's Canal ◽

Lower Complication ◽

Lower Complication Rate ◽

Advanced Glaucoma ◽

Randomised Controlled ◽

Near Future

New surgical strategies for open-angle glaucoma aim to re-establish the physiological aqueous outflow by directly targeting the site of maximal resistance, i.e. the juxtacanalicular meshwork and inner wall of Schlemm’s canal. Canaloplasty uses anab externoapproach, whereas Trabectome (trabeculotomy) and trabecular micro-bypass (iStent) use anab internoapproach. They all work independently of a filtering bleb and have an inherently lower complication rate than trabeculectomy. Preliminary data suggest that they lower intraocular pressure (IOP) to the mid-teens and are more efficient in combination with phacoemulsification. However, their ability to lower IOP is limited by the level of the episcleral venous pressure. Its good safety profile means that Schlemm’s canal surgery may become more popular in the near future, but the outcome of these procedures still needs to be validated in long-term randomised, controlled studies.

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Technique for identifying Schlemm's canal in paediatric glaucoma surgery

British Journal of Ophthalmology ◽

10.1136/bjophthalmol-2014-305164 ◽

2015 ◽

Vol 99 (5) ◽

pp. 715-716

Author(s):

Anagha Medsinge ◽

Ken K Nischal

Keyword(s):

Glaucoma Surgery ◽

Schlemm’S Canal ◽

Schlemm's Canal

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Comparison of Surgical Outcomes between Canaloplasty and Schlemm’s Canal Scaffold at 24 Months’ Follow-Up

Journal of Ophthalmology ◽

10.1155/2016/3410469 ◽

2016 ◽

Vol 2016 ◽

pp. 1-5 ◽

Cited By ~ 18

Author(s):

Stefano A. Gandolfi ◽

Nicola Ungaro ◽

Stella Ghirardini ◽

Maria Grazia Tardini ◽

Paolo Mora

Keyword(s):

Safety Profile ◽

Surgical Outcomes ◽

Clinical Success ◽

Open Angle Glaucoma ◽

Glaucoma Surgery ◽

Open Angle ◽

Schlemm’S Canal ◽

Comparable Rate ◽

Schlemm's Canal

The results of canaloplasty (CP) and Hydrus Microstent (HM) implantation were retrospectively compared at 24 months’ follow-up in a cohort of subjects referred to our Institution for uncontrolled IOP in primary or secondary (e.g., pseudoexfoliative and pigmentary) open-angle glaucoma. The outcome was labelled as “complete” success, “qualified” success, or “failure” if, two years after surgery, the eyes operated on needed “no” hypotensive medications, “some” hypotensive medications, or further glaucoma surgery to attain the target IOP, respectively. Both CP and HM implant allowed significant IOP reductions, with comparable rate of clinical success and safety profile. A slightly (albeit not significant) better trend for a “complete” clinical success was observed in the CP group.

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