Blood Reflux Into Schlemm's Canal

Phelps, Charles D.; Asseff, Carl F.; Weisman, Robert L.; Podos, Steven M.; Becker, Bernard

doi:10.1001/archopht.1972.01000030627011

Cited by 20 publications

(7 citation statements)

References 14 publications

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“…Changes in cellularity and extracellular matrix elements are associated with the glaucoma process in both animal models and in glaucoma patients. 44 – 50 Pulsatile aqueous flow progressively decreases and is eventually lost as the glaucoma process worsens. 44 – 46 In glaucoma patients, miotics transiently restore pulsatile aqueous flow into episcleral veins followed by a drop in IOP that persists throughout the duration of action of the drug.…”

Section: Discussionmentioning

confidence: 99%

Quantification of Pulse-Dependent Trabecular Meshwork Motion in Normal Humans Using Phase-Sensitive OCT

Chen

Song

Johnstone

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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PurposeThe purpose of this study was to characterize the pulsatile motion of trabecular meshwork (TM) in normal subjects and demonstrate its changes in accommodation with phase-sensitive optical coherence tomography (PhS-OCT).MethodsA new PhS-OCT laboratory prototype was designed to measure pulsatile TM motion in 13 healthy humans. Two sets of images were captured in 10 subjects, first with best corrective refraction and the other with an additional 3.0 diopters of accommodation. In each image, both maximum velocity (MV) and cumulative displacement (CD) in two selected regions of TM, the internal (IMV and ICD) and external (EMV and ECD) region, were measured.ResultsFor all parameters the intraclass correlation coefficient was >0.75. Neither MV nor CD was significantly different between eyes in individual subjects (PIMV = 0.967, PEMV = 0.391, PICD = 0.603, PECD = 0.482). In 26 eyes, with best corrective refraction, the EMV was higher than the IMV (23.9 ± 9.8 vs. 18.9 ± 8.08 μm/s; P = 0.0001), as was the ECD compared with the ICD (0.340 ±0.125 vs. 0.264 ± 0.111 μm; P = 0.000004). With accommodation, MV and CD significantly increased (PIMV = 0.0003, PEMV = 0.0003, PICD = 0.019, and PECD = 0.007), whereas MV and CD in the external region were still larger than those in the internal area (PEMV vs. IMV = 0.009, PECD vs. ICD = 0.023).ConclusionsThis study demonstrates the differences in TM motion between the internal and external regions of TM and displays its change with accommodation. The findings and good reproducibility suggest PhS-OCT helps to understand TM function in regulation of IOP, and, with further refinements, it may be useful in clinical management of glaucoma.

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Section: Discussionmentioning

confidence: 99%

Quantification of Pulse-Dependent Trabecular Meshwork Motion in Normal Humans Using Phase-Sensitive OCT

Chen

Song

Johnstone

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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“…Our results are in line with those in previous clinical studies indicating an inverse relation between IOP and blood reflux. 17,21,23 Experimental studies further showed that the canal becomes much narrower as the TM expands into the lumen of the canal with increasing IOP, 46,47 risking collapse at high IOP levels. 48 It has been suggested that at an IOP of 40 mm Hg, the canal may be largely collapsed, 49 except at the site of the CC ostia, where bridging septae may assist in the prevention of such a collapse.…”

Section: Discussionmentioning

confidence: 99%

Clinical Evaluation of the Aqueous Outflow System in Primary Open-Angle Glaucoma for Canaloplasty

Grieshaber

Pienaar

Olivier

et al. 2010

Invest. Ophthalmol. Vis. Sci.

129

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High mean IOP may be associated with poor blood reflux and filling of SC. A collapsed canal, probably secondary to high IOP, may be an underestimated sign in black African patients with POAG. The quality of blood reflux and episcleral venous egress may both be predictive of the level of IOP after surgery. Provocative gonioscopy and channelography may reflect the function of the outflow pathway and may be helpful in assessing the surgical outcome of canaloplasty.

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“…Clinical compression of the episcleral veins during gonioscopy causes a reversal of the usual pressure gradient between the anterior chamber (AC) and SC. Pressure in SC is then higher than in the AC, and the TM moves toward the AC as blood refluxes into the canal ( Smith, 1956 ; Schirmer, 1969 , 1971 ; Suson and Schultz, 1969 ; Phelps et al, 1972 ). SC filling begins in 5–10 s and finishes in 15–30 s ( Schirmer, 1971 ).…”

Section: Clinical Science: An Aqueous Outflow Pump That Fails In Glaucomamentioning

confidence: 99%

Aqueous outflow regulation – 21st century concepts

Johnstone

Chen

Tan

et al. 2021

Progress in Retinal and Eye Research

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We propose an integrated model of aqueous outflow control that employs a pump-conduit system in this article. Our model exploits accepted physiologic regulatory mechanisms such as those of the arterial, venous, and lymphatic systems. Here, we also provide a framework for developing novel diagnostic and therapeutic strategies to improve glaucoma patient care. In the model, the trabecular meshwork distends and recoils in response to continuous physiologic IOP transients like the ocular pulse, blinking, and eye movement. The elasticity of the trabecular meshwork determines cyclic volume changes in Schlemm’s canal (SC). Tube-like SC inlet valves provide aqueous entry into the canal, and outlet valve leaflets at collector channels control aqueous exit from SC. Connections between the pressure-sensing trabecular meshwork and the outlet valve leaflets dynamically control flow from SC. Normal function requires regulation of the trabecular meshwork properties that determine distention and recoil. The aqueous pump-conduit provides short-term pressure control by varying stroke volume in response to pressure changes. Modulating TM constituents that regulate stroke volume provides long-term control. The aqueous outflow pump fails in glaucoma due to the loss of trabecular tissue elastance, as well as alterations in ciliary body tension. These processes lead to SC wall apposition and loss of motion. Visible evidence of pump failure includes a lack of pulsatile aqueous discharge into aqueous veins and reduced ability to reflux blood into SC. These alterations in the functional properties are challenging to monitor clinically. Phase-sensitive OCT now permits noninvasive, quantitative measurement of pulse-dependent TM motion in humans. This proposed conceptual model and related techniques offer a novel framework for understanding mechanisms, improving management, and development of therapeutic options for glaucoma.

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Blood Reflux Into Schlemm's Canal

Cited by 20 publications

References 14 publications

Quantification of Pulse-Dependent Trabecular Meshwork Motion in Normal Humans Using Phase-Sensitive OCT

Quantification of Pulse-Dependent Trabecular Meshwork Motion in Normal Humans Using Phase-Sensitive OCT

Clinical Evaluation of the Aqueous Outflow System in Primary Open-Angle Glaucoma for Canaloplasty

Aqueous outflow regulation – 21st century concepts

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