Trabecular Bypass: Effect of Schlemm’s Canal and Collector Channel Dilation

2004 ◽  
Author(s):  
Jianbo Zhou ◽  
Gregory T. Smedley
Keyword(s):  
Intraocular Pressure ◽  
Second Order ◽  
Polynomial Equations ◽  
Outflow Resistance ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Elevated Intraocular Pressure ◽  
Order Polynomial ◽  
Trabecular Bypass

An ocular outflow model is proposed to theorize the effect of Schlemm’s canal (SC) and/or collector channel (CC) dilation combined with a trabecular bypass on elevated intraocular pressure (IOP) in glaucomatous eyes. The dilated height of the elliptic SC is largest at the bypass and linearly deceases to the non-dilated height over the dilated circumferential length. The CC dilation is modeled with a reduced outflow resistance of second order polynomial. Equations governing the pressure and flow in SC are solved numerically. The model predicts that the IOP is reduced substantially with moderate dilation from the normal 20 μm to 40 μm at the bypass. SC dilation is more effective for eyes with smaller SC. The dilation of CC can also significantly lower the IOP. With the trabecular bypass alone, the elevated IOP is expected to drop to the mid-to-high teens. The IOP can be further reduced by another 3 to 6 mmHg with moderate SC and CC dilation.

Differential P1-purinergic modulation of human Schlemm's canal inner-wall cells

2005 ◽  
Vol 288 (4) ◽  
pp. C784-C794 ◽  
Author(s):  
Mike O. Karl ◽  
Johannes C. Fleischhauer ◽  
W. Daniel Stamer ◽  
Kim Peterson-Yantorno ◽  
Claire H. Mitchell ◽  
...  
Keyword(s):  
Intraocular Pressure ◽  
Aqueous Humor ◽  
Adenosine Receptors ◽  
Outer Wall ◽  
Outflow Resistance ◽  
Schlemm’S Canal ◽  
Adenosine Receptor Agonists ◽  
Schlemm's Canal ◽  
Aqueous Humor Flow

Intraocular pressure is directly dependent on aqueous humor flow into, and resistance to flow out of, the eye. Adenosine has complex effects on intraocular pressure. Stimulation of A1and A2Aadenosine receptors changes intraocular pressure oppositely, likely through opposing actions on the outflow of aqueous humor. While the cellular sites regulating outflow resistance are unknown, the cells lining the inner wall of Schlemm's canal (SC) are a likely regulatory site. We applied selective adenosine receptor agonists to SC cells in vitro to compare the responses to A1and A2Astimulation. Parallel studies were conducted with human inner-wall SC cells isolated by a novel enzyme-assisted technique and with cannula-derived mixed inner- and outer-wall SC cells. A1agonists increased whole cell currents of both inner-wall and cannula-derived SC cells. An A2Aagonist reduced currents most consistently in specifically inner-wall SC cells. Those currents were also increased by A2B, but not consistently affected by A3, stimulation. A1, A2A, and A3agonists all increased SC-cell intracellular Ca2+. The electrophysiological results are consistent with the possibility that inner-wall SC cells may mediate the previously reported modulatory effects of adenosine on outflow resistance. The results are also consistent with the presence of functional A2B, as well as A1, A2A, and A3adenosine receptors in SC cells.

Endothelial Tyrosine Kinase Tie1 Is Required for Normal Schlemm’s Canal Development

2022 ◽  
Author(s):  
Jing Du ◽  
Benjamin R. Thomson ◽  
Tuncer Onay ◽  
Susan E. Quaggin
Keyword(s):  
Intraocular Pressure ◽  
Quantitative Polymerase Chain Reaction ◽  
Schlemm’S Canal ◽  
Knock Out ◽  
Schlemm's Canal ◽  
Elevated Intraocular Pressure ◽  
Knock Out Mice ◽  
And Function ◽  
The Impact

Background: Schlemm’s canal (SC) is a large vessel residing in the iridocorneal angle and is required to regulate aqueous humor outflow. Normal SC structure and function is indispensable for maintaining normal intraocular pressure, and elevated intraocular pressure is a risk factor for development of glaucoma. Recent reports have identified a key role of the angiopoietin-Tie2 pathway for SC development and function; however, the role of the orphan receptor Tie1 has not been clarified. Methods: We used Tie1 knock out mice to study the function of Tie1 in SC development and function. Real-time quantitative polymerase chain reaction and Western blot analyses were used to verify Tie1 deletion. High-resolution microscopy of mouse SC whole mount and cross sections were used to study SC morphology. Measurement of intraocular pressure in live mice was used to study the impact of Tie1 on SC function. Results: Tie1 is highly expressed in both human and mouse SC. Tie1 knock out mice display hypomorphic SC and elevated intraocular pressure as a result of attenuated SC development. Conclusions: Tie1 is indispensable for SC development and function, supporting it as a novel target for future SC-targeted glaucoma therapies and a candidate gene for glaucoma in humans.

A Novel 8-mm Schlemm's Canal Scaffold Reduces Outflow Resistance in a Human Anterior Segment Perfusion Model

2013 ◽  
Vol 54 (3) ◽  
pp. 1698 ◽  
Author(s):  
Vikas Gulati ◽  
Shan Fan ◽  
Cassandra L. Hays ◽  
Thomas W. Samuelson ◽  
Iqbal Ike K. Ahmed ◽  
...  
Keyword(s):  
Anterior Segment ◽  
Outflow Resistance ◽  
Schlemm’S Canal ◽  
Schlemm's Canal ◽  
Perfusion Model

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 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.

scholarly journals Shear Stress in Schlemm’s Canal as a Sensor of Intraocular Pressure

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fiona McDonnell ◽  
Kristin M. Perkumas ◽  
Nicole E. Ashpole ◽  
Joan Kalnitsky ◽  
Joseph M. Sherwood ◽  
...  
Keyword(s):  
Shear Stress ◽  
Intraocular Pressure ◽  
Schlemm’S Canal ◽  
Schlemm's Canal

scholarly journals Anterior Segment Optical Coherence Tomography Signs of Local Dilatation Effect of a Micro-Stent on Schlemm’s Canal

2018 ◽  
Vol 10 (2) ◽  
pp. 184-187
Author(s):  
Kevin Gillmann ◽  
Giorgio Enrico Bravetti ◽  
Kaweh Mansouri ◽  
André Mermoud
Keyword(s):  
Optical Coherence Tomography ◽  
Trabecular Meshwork ◽  
Anterior Segment ◽  
Optical Coherence ◽  
Schlemm’S Canal ◽  
New Device ◽  
Schlemm's Canal ◽  
Canal Diameter ◽  
Trabecular Bypass

Introduction: The iStent inject® (Glaukos Corporation, CA, USA) is a relatively new device designed to be implanted ab-interno through the trabecular meshwork. This is, to the best of our knowledge, the first in-vivo description of a trabecular bypass device visualised with anterior segment optical coherence tomography (AS-OCT), and report of its structural effect on Schlemm’s canal. Case Report: A 74 year-old female patient suffering from long-standing primary open-angle glaucoma and nuclear sclerosis underwent cataract surgery combined with the implantation of two iStent injects®. Surgery was uncomplicated and achieved intraocular pressure (-1 mmHg) and medication (-2 molecules) reduction at 6 months. Under AS-OCT (Spectralis OCT, Heidelberg Engineering AG, Germany) the stent appears as a 300 μm long hyper reflective hollow device within the trabecular meshwork. Approximately a third of it protruded into the anterior chamber. Profound OCT signal loss was notable within the shadow of the device. A second AS-OCT section 500 μm beside the microstent shows a markedly dilated Schlemm’s canal, with a major diameter of 390 μm. Discussions: This report confirms that AS-OCT is a suitable technique to assess microstent positioning, and provides a first report on the in-vivo appearance of a functioning stent. It also indicates that iStent injects® could have a tangible effect on adjacent portions of Schlemm’s canal with, in this case, a 220% increase in canal diameter compared to the observed average (122 μm). This suggests the IOP-lowering effect of trabecular bypass devices could rely on a  dual mechanism involving Schlemm’s canal dilatation.

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