Schlemm’s Canal and Collector Channels as Therapeutic Targets

Gong, Haiyan; Francis, Andrew

doi:10.1007/978-1-4614-8348-9_1

Cited by 15 publications

(17 citation statements)

References 72 publications

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“…42 The outflow tract of the eyes is different and has a much more diffuse and connected nexus of vessels with variable caliber. 7 The drainage system just distal to the outer wall of the SC is more similar to the honeycomb pattern of a capillary network, 7,43 but its vessels are larger and collapsible depending on the perfusion pressure. 44 This makes it challenging to use Doppler strategies to compute flow speeds in single vessels.…”

Section: Discussionmentioning

confidence: 99%

Quantification of Focal Outflow Enhancement Using Differential Canalograms

Loewen

Brown

Scott

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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PurposeTo quantify regional changes of conventional outflow caused by ab interno trabeculectomy (AIT).MethodsGonioscopic, plasma-mediated AIT was established in enucleated pig eyes. We developed a program to automatically quantify outflow changes (R, package eye-canalogram, github.com) using a fluorescent tracer reperfusion technique. Trabecular meshwork (TM) ablation was demonstrated with fluorescent spheres in six eyes before formal outflow quantification with two-dye reperfusion canalograms in six additional eyes. Eyes were perfused with a central, intracameral needle at 15 mm Hg. Canalograms and histology were correlated for each eye.ResultsThe pig eye provided a model with high similarity to AIT in human patients. Histology indicated ablation of TM and unroofing of most Schlemm's canal segments. Spheres highlighted additional circumferential and radial outflow beyond the immediate area of ablation. Differential canalograms showed that AIT caused an increase of outflow of 17 ± 5-fold inferonasally, 14 ± 3-fold superonasally, and also an increase in the opposite quadrants with a 2 ± 1-fold increase superotemporally, and 3 ± 3 inferotemporally. Perilimbal specific flow image analysis showed an accelerated nasal filling with an additional perilimbal flow direction into adjacent quadrants.ConclusionsA quantitative, differential canalography technique was developed that allows us to quantify supraphysiological outflow enhancement by AIT.

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Section: Discussionmentioning

confidence: 99%

Quantification of Focal Outflow Enhancement Using Differential Canalograms

Loewen

Brown

Scott

et al. 2016

Invest. Ophthalmol. Vis. Sci.

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“…Elevated IOP was not the only reason for a lack of blood reflux into SC. Aqueous humor drainage preferentially occurs near collector channels (CCs) [ 7 , 29 ]. CC ostia obstructed by TM herniations when IOP increasing and might lead to the SC blood reflux absence from the episcleral venous system into SC, which could help evaluate the patency of the distal outflow pathway [ 30 , 31 ].…”

Section: Discussionmentioning

confidence: 99%

“…Following complete trabeculectomy [ 6 ], 71% of the outflow resistance was eliminated at a perfusion pressure of 25 mmHg, but only 49% of the resistance was eliminated at a normal perfusion pressure of 7 mmHg. Gong et al [ 7 ] reported that one third to one half of the outflow resistance is located distal to the inner wall of SC. These results suggested that pressure-dependent changes in outflow resistance occurred in the TM, SC, and distal to SC [ 4 – 7 ].…”

Section: Introductionmentioning

confidence: 99%

“…Gong et al [ 7 ] reported that one third to one half of the outflow resistance is located distal to the inner wall of SC. These results suggested that pressure-dependent changes in outflow resistance occurred in the TM, SC, and distal to SC [ 4 – 7 ]. Abnormal aqueous humor outflow pathway resistance can result in excess aqueous humor and elevated IOP.…”

Section: Introductionmentioning

confidence: 99%

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Schlemm’s Canal and Trabecular Meshwork in Eyes with Primary Open Angle Glaucoma: A Comparative Study Using High-Frequency Ultrasound Biomicroscopy

Yan

Chen

et al. 2016

PLoS ONE

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We investigated in vivo changes in Schlemm’s canal and the trabecular meshwork in eyes with primary open angle glaucoma (POAG). Relationships between Schlemm’s canal diameter, trabecular meshwork thickness, and intraocular pressure (IOP) were examined. Forty POAG patients and 40 normal individuals underwent 80-MHz Ultrasound Biomicroscopy examinations. The Schlemm’s canal and trabecular meshwork were imaged in superior, inferior, nasal and temporal regions. Normal individuals had an observable Schlemm’s canal in 80.3% of sections, a meridional canal diameter of 233.0±34.5 μm, a coronal diameter of 44.5±12.6 μm and a trabecular meshwork thickness of 103.9±11.1 μm, in POAG patients, Schlemm’s canal was observable in 53.1% of sections, a meridional canal diameter of 195.6±31.3 μm, a coronal diameter of 35.7±8.0 μm, and a trabecular meshwork thickness of 88.3±13.2 μm, which significantly differed from normal (both p <0.001). Coronal canal diameter (r = -0.623, p < 0.001) and trabecular meshwork thickness (r = -0.663, p < 0.001) were negatively correlated with IOP, but meridional canal diameter was not (r = -0.160, p = 0.156). Schlemm’s canal was observable in 50.5% and 56.6% of POAG patients with normal (<21 mmHg) and elevated (>21 mmHg) IOP, respectively (χ = 1.159, p = 0.282). Coronal canal diameter was significantly lower in the elevated IOP group (32.6±4.9 μm) than in the normal IOP group (35.7±8.0 μm, p < 0.001). This was also true of trabecular meshwork thickness (81.9±10.0 μm vs. 97.1±12.0 μm, p < 0.001). In conclusion, eyes with POAG had fewer sections with an observable Schlemm’s canal. Canal diameter and trabecular meshwork thickness were also lower than normal in POAG patients. Schlemm’s canal coronal diameter and trabecular meshwork thickness were negatively correlated with IOP.

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“…Channelography and canalography are essentially the same technique that relies on unroofing Schlemm’s canal (SC) with introduction of the tracer (fluorescein, ICG, or trypan blue) [54–59]. The introduction can occur through local injection analogous to a viscocanulostomy surgery or through intermittent deposition from a flexible microcatheter as it is pulled through the eye during canaloplasty surgery.…”

Section: Real-time Techniques For Functional Assessment Of Aqueous Humentioning

confidence: 99%

Aqueous Humor Outflow Structure and Function Imaging At the Bench and Bedside: A Review

Huang

Mohindroo

Weinreb

2016

J Clin Exp Ophthalmol

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Anterior segment glaucoma clinical care and research has recently gained new focus because of novel imaging modalities and the advent of angle-based surgical treatments. Traditional investigation drawn to the trabecular meshwork now emphasizes the entire conventional aqueous humor outflow (AHO) pathway from the anterior chamber to the episcleral vein. AHO investigation can be divided into structural and functional assessments using different methods. The historical basis for studying the anterior segment of the eye and AHO in glaucoma is discussed. Structural studies of AHO are reviewed and include traditional pathological approaches to modern tools such as multi-model two-photon microscopy and optical coherence tomography. Functional assessment focuses on visualizing AHO itself through a variety of non-real-time and real-time techniques such as aqueous angiography. Implications of distal outflow resistance and segmental AHO are discussed with an emphasis on melding bench-side research to viable clinical applications. Through the development of an improved structure: function relationship for AHO in the anterior segment of the normal and diseased eye, a better understanding of the eye with improved therapeutics may be developed.

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Schlemm’s Canal and Collector Channels as Therapeutic Targets

Cited by 15 publications

References 72 publications

Quantification of Focal Outflow Enhancement Using Differential Canalograms

Quantification of Focal Outflow Enhancement Using Differential Canalograms

Schlemm’s Canal and Trabecular Meshwork in Eyes with Primary Open Angle Glaucoma: A Comparative Study Using High-Frequency Ultrasound Biomicroscopy

Aqueous Humor Outflow Structure and Function Imaging At the Bench and Bedside: A Review

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