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

Life ◽  
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.

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

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.

scholarly journals Comparison of Efficacy between 120° and 180° Schlemm’s Canal Incision Microhook Ab Interno Trabeculotomy

2021 ◽  
Vol 10 (14) ◽  
pp. 3181
Author(s):  
Naoki Okada ◽  
Kazuyuki Hirooka ◽  
Hiromitsu Onoe ◽  
Yumiko Murakami ◽  
Hideaki Okumichi ◽  
...  
Keyword(s):  
Surgical Outcomes ◽  
Open Angle Glaucoma ◽  
Case Series ◽  
Glaucoma Surgery ◽  
Success Rates ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Kaplan Meier ◽  
The Mean ◽  
Ab Interno

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.

Complications Common to Nonpenetrating Surgeries

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.

scholarly journals Simultaneous influence of sympathetic autonomic stress on Schlemm’s canal, intraocular pressure and ocular circulation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Wei Chen ◽  
Zhiqi Chen ◽  
Yan Xiang ◽  
Chaohua Deng ◽  
Hong Zhang ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Cold Pressor Test ◽  
Cold Pressor ◽  
Retinal Vessel ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Schlemm’S Canal ◽  
Cold Stimulation ◽  
Cross Sectional ◽  
Schlemm's Canal

AbstractThis study aimed to investigate changes in Schlemm’s canal, intraocular pressure and ocular blood circulation following the activation of the sympathetic nervous system. Twenty healthy volunteers were enrolled in this study. The cold pressor test (CPT) was adopted. Cross-sectional area of Schlemm’s canal (SCAR), superficial and deep retinal vessel densities (s-RVD;d-RVD), pupil diameter (PD), intraocular pressure (IOP), mean ocular perfusion pressure (MOPP) and heart rate variability (HRV) were measured at three time-points: baseline (T0) and 5 min (T1) and 10 min (T2) after the CPT. After cold stimulation, LF/HF index (the ratio of low frenquency and high frenquency) increased significantly. IOP decreased from 16.9 ± 1.9 mmHg at baseline to 16.4 ± 2.7 mmHg at T1 and to 15.2 ± 2.7 mmHg at T2. The nasal cross-sectional area of SCAR (SCAR-n) increased from 6283.9 ± 2696.2 µm2 at baseline to 8392.9 ± 3258.7 µm2 at T1 and to 10422.0 ± 3643.8 µm2 at T2. The temporal cross-sectional area of SCAR (SCAR-t) increased from 6414.5 ± 2218.7 µm2 at baseline to 8610.8 ± 2317.1 µm2 at T1 and to 11544.0 ± 4129.2 µm2 at T2. The expansion of Schlemm’s canal was observed after the CPT might be caused by sympathetic nerve stimulation, subsequently leading to decreased IOP.

Viscocanalostomy: A Pilot Study

1998 ◽  
Vol 8 (2) ◽  
pp. 57-61 ◽  
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.

Multiplanar review of three-dimensional echocardiography gives new insights into the morphology of Ebstein’s malformation

2010 ◽  
Vol 20 (1) ◽  
pp. 49-53 ◽  
Author(s):  
Tara Bharucha ◽  
Robert H. Anderson ◽  
Zek S. Lim ◽  
Joseph J. Vettukattil
Keyword(s):  
Three Dimensional ◽  
Right Ventricular Outflow Tract ◽  
Ventricular Outflow Tract ◽  
Diagnostic Features ◽  
Cross Sectional ◽  
Dynamic Morphology ◽  
Clear Differentiation ◽  
Dimensional Echocardiography ◽  
Three Dimensional Echocardiography ◽  
The Right

AbstractIntroductionWe aimed to assess the ability of the multiplanar review modality of three-dimensional echocardiography to examine the dynamic morphology and the functional characteristics of malformed tricuspid valves in patients previously identified as having Ebstein’s malformation. Based on these characteristics, we attempted to differentiate Ebstein’s malformation from tricuspid valvar dysplasia.MethodsUsing three-dimensional multiplanar review, analysed with either Qlab 6.0 or Tomtech Image Arena 3.0, we studied 23 patients, aged from 1 day to 70 years, previously diagnosed using cross-sectional echocardiography as having Ebstein’s malformation.ResultsUsing the features of rotational abnormality, and the orientation, of the effective tricuspid valvar orifice as diagnostic features of Ebstein’s malformation, we reclassified 11 patients (48 per cent) as exhibiting tricuspid valvar dysplasia. In addition, we studied the dynamic morphology as well as the function of the tricuspid valve. Surgical treatment was undertaken on 10 patients, revealing good correlation with the findings obtained using three-dimensional multiplanar review. In those with Ebstein’s malformation, we found varying degrees of rotation, with the effective valvar orifice always directed towards the right ventricular outflow tract. The opening of the orifice of dysplastic tricuspid valves, in contrast, was towards the apex of the right ventricle. The degree of delamination, and abnormalities of subcordal apparatus, were similar in the two groups.DiscussionThree-dimensional multiplanar review permits accurate definition of the dynamic morphology of Ebstein’s malformation, permitting clear differentiation from tricuspid valvar dysplasia.

scholarly journals Histological Findings in the Trabecular Meshwork of a Patient with Atopic Glaucoma

2017 ◽  
Vol 11 (1) ◽  
pp. 103-106 ◽  
Author(s):  
Satoru Kase ◽  
Shiki Chin ◽  
Teruhiko Hamanaka ◽  
Yasuhiro Shinmei ◽  
Takeshi Ohguchi ◽  
...  
Keyword(s):  
Atopic Dermatitis ◽  
Trabecular Meshwork ◽  
Severe Atopic Dermatitis ◽  
Histological Findings ◽  
Schlemm’S Canal ◽  
Blurred Vision ◽  
Schlemm's Canal ◽  
The Right ◽  
Histological Results ◽  
Topical Medications

Purpose: The aim of this study was to report a case of atopic dermatitis showing elevated intraocular pressure (IOP) beyond the baseline levels followed by a modified 360-degree suture trabeculotomy, and to analyze the histological findings in the trabecular meshwork. Methods: A 40-year-old male suffered from blurred vision in the right eye (OD). He had a medical history of severe atopic dermatitis and intraocular lens implantation OU due to atopic cataract. At the initial presentation, the visual acuity was 0.03, and IOP was 35 mmHg OD. Slit-lamp examination demonstrated corneal epithelial edema OD. Increased IOP was refractory to several topical medications. The patient underwent a modified 360-degree suture trabeculotomy. The visual field defect, however, deteriorated with persistently high IOP. The patient underwent trabeculectomy together with drainage implant surgery. In the outflow routes, although there seemed to be an opening of Schlemm’s canal into the anterior chamber, there was no endothelium of the canal in the region of its opening. The fibrotic changes were conspicuous around Schlemm’s canal. Conclusion: The histological results indicated that trabeculotomy might not be an appropriate treatment for patients with atopic glaucoma, possibly because of excessive repair to the newly created uveoscleral outflow in addition to the increased postoperative fibrosis in the trabecular meshwork and Schlemm’s canal.

Angle and Nonpenetrating Glaucoma Surgery

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.

scholarly journals Pharmacological regulation of outflow resistance distal to Schlemm’s canal

2018 ◽  
Vol 315 (1) ◽  
pp. C44-C51 ◽  
Author(s):  
Fiona McDonnell ◽  
W. Michael Dismuke ◽  
Darryl R. Overby ◽  
W. Daniel Stamer
Keyword(s):  
Dynamic Range ◽  
Smooth Muscle Actin ◽  
Anterior Segment ◽  
Physiological Model ◽  
Outflow Resistance ◽  
Schlemm’S Canal ◽  
Outflow Facility ◽  
Schlemm's Canal ◽  
Anterior Segments ◽  
Outflow Pathway

The trabecular meshwork (TM) and Schlemm’s canal generate the majority of outflow resistance; however, the distal regions of the conventional outflow pathway account for 25–50% of total resistance. Sections of distal vessels are surrounded by α-smooth muscle actin-containing cells, indicating that they may be vasoregulated. This study examined the effect of a potent vasodilator, nitric oxide (NO), and its physiological antagonist, endothelin-1 (ET-1), on the regulation of outflow resistance in the distal regions of the conventional outflow pathway. Using a physiological model of the conventional outflow pathway, human and porcine anterior segments were perfused in organ culture under constant flow conditions, while intrachamber pressure was continually monitored. For porcine anterior segments, a stable baseline outflow facility with TM intact was first achieved before anterior segments were removed and a trabeculotomy was performed. For human anterior segments, a trabeculotomy was immediately performed. In human anterior segments, 100 nM ET-1 significantly decreased distal outflow facility from 0.49 ± 0.26 to 0.31 ±  0.18 (mean ± SD) µl·min−1·mmHg, P < 0.01. Perfusion with 100 µM diethylenetriamine-NO in the presence of 1 nM ET-1 immediately reversed ET-1 effects, significantly increasing distal outflow facility to 0.54 ± 0.35 µl·min−1·mmHg, P = 0.01. Similar results were obtained in porcine anterior segment experiments. Therefore, data show a dynamic range of resistance generation by distal vessels in both the human and the porcine conventional outflow pathways. Interestingly, maximal contraction of vessels in the distal outflow tract of trabeculotomized eyes generated resistance very near physiological levels for both species having an intact TM.

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