The pressures in the episcleral veins, Schlemm's canal and the trabecular meshwork in monkeys: Effects of changes in intraocular pressure

1989 ◽  
Vol 49 (4) ◽  
pp. 645-663 ◽  
Author(s):  
Olav Mäepea ◽  
Anders Bill
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Schlemm’S Canal ◽  
Schlemm's Canal

scholarly journals Morphological changes in the trabecular meshwork and Schlemm’s canal after treatment with topical intraocular pressure-lowering agents

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ji-Hye Park ◽  
Hyun Woo Chung ◽  
Eun Gyu Yoon ◽  
Min Jung Ji ◽  
Chungkwon Yoo ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Morphological Changes ◽  
Open Angle Glaucoma ◽  
Anterior Segment ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Before And After ◽  
Treatment Naïve ◽  
Aqueous Outflow

AbstractGlaucoma treatment is usually initiated with topical medication that lowers the intraocular pressure (IOP) by reducing the aqueous production, enhancing the aqueous outflow, or both. However, the effect of topical IOP-lowering medications on the microstructures of the aqueous outflow pathway are relatively unknown. In this retrospective, observational study, 56 treatment-naïve patients with primary open-angle glaucoma were enrolled. Images of the nasal and temporal corneoscleral limbus were obtained using anterior segment optical coherence tomography (AS-OCT). The conjunctival vessels and iris anatomy were used as landmarks to select the same limbal area scan, and the trabecular meshwork (TM) width, TM thickness, and Schlemm’s canal (SC) area were measured before and after using the IOP-lowering agents for 3 months. Among the 56 patients enrolled, 33 patients used prostaglandin (PG) analogues, and 23 patients used dorzolamide/timolol fixed combination (DTFC). After 3 months of DTFC usage, the TM width, TM thickness, and SC area did not show significant changes in either the nasal or temporal sectors. Conversely, after prostaglandin analog usage, the TM thickness significantly increased, and the SC area significantly decreased (all P < 0.01). These findings warrant a deeper investigation into their relationship to aqueous outflow through the conventional and unconventional outflow pathways after treatment with PG analogues.

scholarly journals Influence of Exercise on Intraocular Pressure, Schlemm's Canal, and the Trabecular Meshwork

2016 ◽  
Vol 57 (11) ◽  
pp. 4733 ◽  
Author(s):  
Xiaoqin Yan ◽  
Mu Li ◽  
Yinwei Song ◽  
Jingmin Guo ◽  
Yin Zhao ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Schlemm’S Canal ◽  
Schlemm's Canal

Combined Circumferential Canaloplasty and Trabeculotomy Ab Interno with the OMNI Surgical System

2021 ◽  
pp. 1-9
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
New Technology ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Surgical Device ◽  
Outflow Pathway ◽  
Consequent Increase ◽  
Surgical System ◽  
Ab Interno

In the normal eye the conventional outflow pathway is responsible for the majority of aqueous humor egress and plays a key role in the maintenance of healthy intraocular pressure. However, in the glaucomatous eye pathologic changes to the pathway in the trabecular meshwork, Schlemm’s canal, and collector channel ostia can introduce abnormal resistance to outflow with consequent increase in intraocular pressure. The OMNI Surgical System (Sight Sciences, Menlo Park, CA USA) is a relatively new surgical device and the only one that combines two ab interno minimally invasive treatments in a single procedure, canaloplasty and trabeculotomy. This new technology allows surgeons to address outflow resistance wherever it may be, both proximally (juxtacanalicular trabecular meshwork and inner wall of Schlemm’s canal), and distally (Schlemm’s canal and the collector channels). This review covers several recent clinical studies of the OMNI device with the aim of collating what is known and what remains to be learned.

Stegmann Canal Expander for canaloplasty: A novel technique

2018 ◽  
Vol 28 (4) ◽  
pp. 472-478 ◽  
Author(s):  
Matthias C Grieshaber
Keyword(s):  
Intraocular Pressure ◽  
Trabecular Meshwork ◽  
Deep Sclerectomy ◽  
Specific Design ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Novel Technique ◽  
Dissection Technique ◽  
Aqueous Outflow ◽  
Outflow System

Introduction: The concept of canaloplasty is to increase aqueous egress through all structures that control the aqueous outflow, such as the trabecular meshwork, Schlemm’s canal, and collector channels, by viscomodulation and by placing of a suture stent into the canal. Clinical studies show canaloplasty to be safe and efficient in lowering the intraocular pressure; however, proper knotting of the tensioning suture is technically challenging and even impossible if circumferential cannulation cannot be achieved; furthermore, protrusion of the suture stent is a potential lifelong risk. Methods: The specific design of the Stegmann Canal Expander allows a permanent expansion of the canal and distension of the trabecular meshwork. Two expanders are implanted on either side of the surgically created ostium of Schlemm’s canal to treat half of the circumferential outflow system. This article describes the technique step by step, provides the clinician with surgical pearls, and highlights the management of adverse events. Results: Technically, implantation of the Stegmann Canal Expander is simple and does not require a long learning curve, compared to placing and knotting a tensioning suture. Most issues are related to the two-flap dissection technique (deep sclerectomy technique) and not to implantation of the Stegmann Canal Expander. Intraocular pressure reduction without medications to the low teens can be achieved. Conclusions: The Stegmann Canal Expander is a novel micro-device that has the potential to make canaloplasty a simplified, more controlled, and reproducible surgical procedure.

Three-dimensional confocal laser microscopy of fibronectin in normal and glaucomatous eyes

1991 ◽  
Vol 49 ◽  
pp. 402-403
Author(s):  
Annelies W. de Kater ◽  
R. Rand Allingham ◽  
Doug S. Bowman ◽  
Fredric S. Fay
Keyword(s):  
Fluid Flow ◽  
Intraocular Pressure ◽  
Aqueous Humor ◽  
Trabecular Meshwork ◽  
Open Angle Glaucoma ◽  
Confocal Laser ◽  
Schlemm’S Canal ◽  
Endothelial Lining ◽  
Schlemm's Canal ◽  
Specific Distribution

Aqueous humor exits the anterior chamber of the eye through the trabecular meshwork into Schlemm's canal, a vessel which drains into the systemic circulatory system. The aqueous humor crosses the endothelial lining of Schlemm's canal by means of focal invaginations which form pores and allow digress of fluid into the canal. The trabecular meshwork provides a resistance to fluid flow resulting in a physiologic intraocular pressure in normal eyes. The region adjacent to Schlemm's canal appears to be the site of highest resistance to fluid flow in both normal and glaucomatous eyes. In eyes with primary open angle glaucoma (POAG) the resistance to fluid flow through the trabecular meshwork is abnormally high, causing an elevated intraocular pressure (IOP), which can lead to irreversible damage of the optic nerve and blindness. A definitive morphologic correlate of this disease has not been discovered. Immunohistochemical studies localizing fibronectin in unfixed frozen sections of human eyes have shown elevated levels of fibronectin in the eyes with glaucoma, however the specific distribution of this protein has not been determined due to poor tissue preservation.

scholarly journals An imaged-based inverse finite element method to determine in-vivo mechanical properties of the human trabecular meshwork

2017 ◽  
Vol 1 (3) ◽  
pp. 100-111
Author(s):  
Anup D. Pant ◽  
Larry Kagemann ◽  
Joel S. Schuman ◽  
Ian A. Sigal ◽  
Rouzbeh Amini
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Shear Modulus ◽  
Trabecular Meshwork ◽  
Computational Simulation ◽  
Optimization Technique ◽  
Schlemm’S Canal ◽  
Aqueous Humor Outflow ◽  
Schlemm's Canal

Aim/Purpose: Previous studies have shown that the trabecular meshwork (TM) is mechanically stiffer in glaucomatous eyes as compared to normal eyes. It is believed that elevated TM stiffness increases resistance to the aqueous humor outflow, producing increased intraocular pressure (IOP).It would be advantageous to measure TM mechanical properties in vivo, as these properties are believed to play an important role in the pathophysiology of glaucoma and could be useful for identifying potential risk factors.  The purpose of this study was to develop a method to estimate in-vivo TM mechanical properties using clinically available exams and computer simulations.Design: Inverse finite element simulationMethods: A finite element model of the TM was constructed from optical coherence tomography (OCT) images of a healthy volunteer before and during IOP elevation. An axisymmetric model of the TM was then constructed. Images of the TM at a baseline IOP level of 11, and elevated level of 23 mmHg were treated as the undeformed and deformed configurations, respectively. An inverse modeling technique was subsequently used to estimate the TM shear modulus (G). An optimization technique was used to find the shear modulus that minimized the difference between Schlemm’s canal area in the in-vivo images and simulations.Results: Upon completion of inverse finite element modeling, the simulated area of the Schlemm’s canal changed from 8,889 μm2 to 2,088 μm2, similar to the experimentally measured areal change of the canal (from 8,889 μm2 to 2,100 μm2). The calculated value of shear modulus was found to be 1.93 kPa,  (implying an approximate Young’s modulus of 5.75 kPa), which is consistent with previous ex-vivo measurements.Conclusion: The combined imaging and computational simulation technique provides a unique approach to calculate the mechanical properties of the TM in vivo without any surgical intervention. Quantification of such mechanical properties will help us examine the mechanistic role of TM biomechanics in the regulation of IOP in healthy and glaucomatous eyes. 

scholarly journals Schlemm's canal and trabecular meshwork morphology in high myopia

2018 ◽  
Vol 38 (3) ◽  
pp. 266-272 ◽  
Author(s):  
Zhiqi Chen ◽  
Yinwei Song ◽  
Mu Li ◽  
Wei Chen ◽  
Shiliang Liu ◽  
...  
Keyword(s):  
Trabecular Meshwork ◽  
High Myopia ◽  
Schlemm’S Canal ◽  
Schlemm's Canal

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.

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