Effects of viscoelastic injection into Schlemm’s canal in primate and human eyes

Smit, Barbara; Johnstone, Murray

doi:10.1016/s0161-6420(01)01006-5

Cited by 97 publications

(85 citation statements)

References 20 publications

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“…44 The effects of pressure-induced reversal have, in addition, been studied in the laboratory and shown to cause marked changes in SC structural relationships. 32 Devices currently being inserted into SC in the operating room to bypass the TM are thought to achieve their best effect when placed near CCO; at the same time, efforts are made to avoid damage to or occlusion of CCO. The positioning of MIGS devices has been evaluated through imaging with SEM, 45,46 but not OCT. Device placement requirements illustrate the need for in vivo imaging tools to inform device development and to optimize device placement, thereby enabling improvement of clinical outcomes.…”

Section: Discussionmentioning

confidence: 99%

“…Scanning electron microscopy (SEM) was used to image radial sections cut to a thickness of ∼100 μm from each quadrant of the limbus of a 13.9-year-old, 6.7-kg nemestrina monkey. Following viscoelastic SC dilation by a previously described technique, 32 the sections were fixed with Karnovsky's solution. Further processing involved dehydration with graded alcohols and then postfixation with osmium, tannic acid, and uranyl acetate.…”

Section: Tissue Preparationmentioning

confidence: 99%

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Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

et al. 2014

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Abstract. The aqueous outflow system (AOS) is responsible for maintaining normal intraocular pressure (IOP) in the eye. Structures of the AOS have an active role in regulating IOP in healthy eyes and these structures become abnormal in the eyes with glaucoma. We describe a newly developed system platform to obtain high-resolution images of the AOS structures. By incorporating spectral domain optical coherence tomography (SD-OCT), the platform allows us to systematically control, image, and quantitate the responses of AOS tissue to pressure with a millisecond resolution of pulsed flow. We use SD-OCT to image radial limbal segments from the surface of the trabecular meshwork (TM) with a spatial resolution of ∼5 μm in ex vivo nonhuman primate eyes. We carefully insert a cannula into Schlemm's canal (SC) to control both pressures and flow rates. The experimental results demonstrate the capability of the platform to visualize the unprecedented details of AOS tissue components comparable to that delivered by scanning electron microscopy, as well as to delineate the complex pressure-dependent relationships among the TM, structures within the SC, and collector channel ostia. The described technique provides a new means to characterize the anatomic and pressure-dependent relationships of SC structures, particularly the active motion of collagenous elements at collector channel ostia; such relationships have not previously been amenable to study. Experimental findings suggest that continuing improvements in the OCT imaging of the AOS may provide both insights into the glaucoma enigma and improvements in its management.

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Section: Discussionmentioning

confidence: 99%

Section: Tissue Preparationmentioning

confidence: 99%

Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

et al. 2014

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“…3(a)], which is used as the length (L) of the rectangular box in our model. The anterior-posterior length of SC has been measured to be 230 to 30 μm, 61 which is used as the width (W) of the rectangular box [refer to Fig. 3(b)].…”

Section: Theoretical Considerationsmentioning

confidence: 99%

“…The total height of the box is estimated to be 11 μm. 61 Aqueous flow has been estimated to be 1.5 μl/min. 62,63 For a 60-beats-per-minute heart rate, the aqueous stroke volume with each pulse wave, which corresponds to the change in SC volume (ΔV) per heartbeat, is therefore 0.025 μl.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement inex vivononhuman primate eyes

et al. 2012

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Abstract. Glaucoma is a blinding disease for which intraocular pressure (IOP) is the only treatable risk factor. The mean IOP is regulated through the aqueous outflow system, which contains the trabecular meshwork (TM). Considerable evidence indicates that trabecular tissue movement regulates the aqueous outflow and becomes abnormal during glaucoma; however, such motion has thus far escaped detection. The purpose of this study is to describe anovel use of a phase-sensitive optical coherence tomography (PhS-OCT) method to assess pulsedependent TM movement. For this study, we used enucleated monkey eyes, each mounted in an anterior segment holder. A perfusion system was used to control the mean IOP as well as to provide IOP sinusoidal transients (amplitude 3 mmHg, frequency 1 pulse/second) in all experiments. Measurements were carried out at seven graded mean IOPs (5,8,10,20,30,40, and 50 mm Hg). We demonstrate that PhS-OCT is sensitive enough to image/ visualize TM movement synchronous with the pulse-induced IOP transients, providing quantitative measurements of dynamic parameters such as velocity, displacement, and strain rate that are important for assessing the biomechanical compliance of the TM. We find that the largest TM displacement is in the area closest to Schlemm's canal (SC) endothelium. While maintaining constant ocular pulse amplitude, an increase of mean IOP results in a decrease of TM displacement and mean size of the SC. These results demonstrate that the PhS-OCT is a useful imaging technique capable of assessing functional properties necessary to maintain IOP in a healthy range, offering a new diagnostic alternative for glaucoma.

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“…Enlarging a greater part may increase the chance for a more consistent patency of SC and a circumferential flow. 11 The idea of re-establishing the internal physiological pathway was the initiation of the development of a lighted flexible microcatheter (iTrack; iScience Interventional, Menlo Park, CA, USA). In a study on human perfused cadaver eyes, 1801 expansion of SC showed a significant increase in the outflow facility and amount of expansion was related to the relative increase in outflow facility.…”

Section: Introductionmentioning

confidence: 99%

Comparing two tensioning suture sizes for 360° viscocanalostomy (canaloplasty): a randomised controlled trial

Grieshaber

Pienaar

Olivier

et al. 2010

Eye

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Purpose To compare the safety and efficacy of two polypropylene (Prolene) sutures for tensioning of the inner wall of Schlemm's canal (SC) in black African patients with primary open-angle glaucoma (POAG) undergoing canaloplasty. Methods In a prospective randomised trial of 90 patients, canaloplasty was performed with a flexible microcatheter (iTrack-250A) and sodium hyaluronidate 1.4% (Healon GV). After complete circumferential dilatation of the SC, a Prolene suture, either 6-0 Prolene (group 1) or 10-0 Prolene (group 2), was retracted through the SC and tightened leaving tension on the canal and trabecular meshwork. Nd:YAG laser goniopuncture was not performed postoperatively. Results The mean preoperative intraocular pressure (IOP) was 42.7 mm Hg±12.5 (SD) in group 1 and 45.0 mm Hg ± 12.1 (SD) in group 2 (P ¼ 0.70). The mean postoperative IOP without medications was 18.4 mm Hg ± 7.1 (SD) in group 1 and 16.4 mm Hg ± 6.6 (SD) in group 2 at 1 month (P ¼ 0.10), 19.2 mm Hg±6.4 (SD) in group 1 and 16.4 mm Hg±4.9 (SD) at 15 months (P ¼ 0.04). Pressures equal or less than 21, 18, and 16 mm Hg without medications (complete success) at 12 months were 51.0% (95% confidence interval (CI) 0.35-0.73), 34.1% (95% CI 0.21-0.56), and 21.2% (95% CI 0.11-0.42) in group 1, and 76.9% (95% CI 0.62-0.96), 68.8% (95% CI 0.54-0.89), and 53.6% (95% CI 0.38-0.76) in group 2, respectively. In the Cox regression analysis, IOP o18 mm Hg without medications depended significantly on the type of Prolene (hazard ratio (HR) 2.60, 95% CI 1.24-5.46, P ¼ 0.01) and age (HR 1.3, 95% CI 1.03-1.86, P ¼ 0.03), but not on preoperative IOP (HR 1.01, 95% CI 0.99-1.04, P ¼ 0.16) and gender (HR 0.67, 95% CI 0.34-1.33, P ¼ 0.26). No filtering bleb was observed. Intra-and postoperative complications were similarly rare in the two groups and included partial 'cheese-wiring' (2), Descemet's rupture (2), and hyphaema (3). Conclusions In this clinical trial, IOP reduction was substantial in canaloplasty and slightly greater in combination with 10-0 Prolene than 6-0 Prolene sutures at an equally low complication rate. Younger age, but not the level of IOP at surgery, had a positive effect on the amount of IOP reduction, thus suggesting that an early surgical intervention to re-establish physiological outflow offers the best prognosis.

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Effects of viscoelastic injection into Schlemm’s canal in primate and human eyes

Cited by 97 publications

References 20 publications

Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

Platform to investigate aqueous outflow system structure and pressure-dependent motion using high-resolution spectral domain optical coherence tomography

Phase-sensitive optical coherence tomography characterization of pulse-induced trabecular meshwork displacement inex vivononhuman primate eyes

Comparing two tensioning suture sizes for 360° viscocanalostomy (canaloplasty): a randomised controlled trial

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