The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Tin Aung - One of the best experts on this subject based on the ideXlab platform.
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Analysis of Association Between the Insertion Location of Iris Root and Narrow Angle.
Journal of Glaucoma, 2015Co-Authors: Bingsong Wang, Monisha E. Nongpiur, Ning Dong, Tin AungAbstract:To study the association between the insertion location of iris root and narrow angle. This was a prospective observational study. A total of 142 eyes of 142 subjects were recruited, including 78 with narrow angles and 64 normals. All participants underwent ultrasound biomicroscopy and customized software was used to quantitatively analyze the images. An eye was considered to have narrow angle if there was iridotrabecular contact for at least 180 degrees on nonindentation gonioscopy in the primary position. The difference in various parameters between subjects with narrow angle and normal controls were analyzed. The association between the distance from the iris root to Scleral Spur (IrisD) and angle open distance was also analyzed. Significant differences between narrow angle and normal eyes were found for anterior chamber depth (ACD, 2.01±0.26 vs. 2.66±0.34 mm, P≤0.001), anterior chamber width (ACW, 10.96±0.45 vs. 11.19±0.39 mm, P=0.003), IrisD (0.083±0.091 vs. 0.174±0.094 mm, P<0.001), and iris thickness at 1500 µm from the Scleral Spur (IT1500, 0.533±0.087 vs. 0.503±0.081 mm, P=0.007). After adjusting for age, sex, ACD, ACW, and IT1500, a smaller IrisD was associated significantly with narrow angle (odds ratio, 104.3; 95% confidence interval, 5.9-1852, comparing highest with lowest quartile). In terms of distinguishing narrow angle subjects from open angle subjects, IrisD [area under the receiver operator characteristic curve (AUC) 0.76] performed relatively poorer compared with ACD (AUC 0.95). A smaller distance from iris root to Scleral Spur was associated with the presence of narrow angle.
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Associations of iris structural measurements in a Chinese population: the Singapore Chinese Eye Study.
Investigative Ophthalmology & Visual Science, 2013Co-Authors: John Carson Allen, Carol Y. Cheung, David S Friedman, Mingguang He, Monisha E. Nongpiur, Yingfeng Zheng, Tien Yin Wong, Tin AungAbstract:PURPOSE: We determined the ocular biometric and demographic factors associated with iris parameters in Singaporean Chinese persons from a population-based sample. METHODS: Subjects were participants in the Singapore Chinese Eye Study, a population-based cross-sectional study of eye disease. Anterior segment optical coherence tomography images were analyzed using customized software to measure iris thickness at 750 μm from the Scleral Spur (IT750), iris area (I-Area), and iris curvature (I-Curv). Regression analyses were performed to assess the association between iris measurements with a range of demographic and ocular variables. The contribution of each independent variable to the iris parameter of interest was determined sequentially using a stepwise selection algorithm. RESULTS: We included 1473 participants with a mean age of 57.7 + 8.68 years, and 50.6% were men. The mean IT750, I-Area, and I-Curv were 0.46 ± 0.10 mm, 1.49 ± 0.24 mm(2), and 0.25 ± 0.13 mm, respectively. Statistical regression models, including a range of demographic and ocular parameters, explained 59.3%, 41.9%, and 34.3% of the variability in I-Curv, IT750, and I-Area, respectively. Angle opening distance at 750 μm from the Scleral Spur (AOD750) was the single factor associated most strongly with I-Curv, and explained 46.6% of its variation. CONCLUSIONS: A significant proportion of the variation in iris area, curvature, and thickness was not explained by other ocular and demographic parameters. Iris curvature was associated strongly with angle width, and of all parameters investigated, AOD750 was most highly correlated with iris curvature.
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assessment of trabecular meshwork width using swept source optical coherence tomography
Graefes Archive for Clinical and Experimental Ophthalmology, 2013Co-Authors: Mani Baskaran, Carol Y. Cheung, Lisandro M Sakata, David S Friedman, Ce Zheng, Shamira A. Perera, Anita S Chan, Tin AungAbstract:Purpose Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the Scleral Spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement.
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Analysis of Anterior Segment Dynamics Using Anterior Segment Optical Coherence Tomography Before and After Laser Peripheral Iridotomy
JAMA Ophthalmology, 2013Co-Authors: Ce Zheng, David S Friedman, Celeste P. Guzman, Carol Yim-lui Cheung, Yingke He, Arun Narayanaswamy, Paul T.k. Chew, Shamira A. Perera, Tin AungAbstract:Objective To evaluate changes in the speed of pupil constriction and in anterior segment parameters after laser peripheral iridotomy (LPI) in patients with angle closure using anterior segment optical coherence tomography. Methods In this prospective observational study, videos of pupil and anterior segment changes in response to illumination were captured with real-time video recording using anterior segment optical coherence tomography and were analyzed frame by frame before and after LPI. Customized software was used to measure the speed of pupil constriction and changes in anterior chamber depth and anterior chamber area, as well as iris thickness at 750 μm from the Scleral Spur, at the sphincter muscle region (0.75 mm from the pupillary margin), and at the mid-iris location (half the distance between the Scleral Spur and the pupillary margin). Pupil diameter, angle opening distance, and trabecular–iris space area at 500 μm from the Scleral Spur were determined. The speed of pupil constriction was defined as the rate of pupil diameter change in response to illumination. Results Twenty-nine patients were included. Most were Chinese (26 of 29 [90%]) and female (18 of 29 [62%]). The anterior chamber area, angle opening distance at 500 μm from the Scleral Spur, and trabecular–iris space area at 500 μm from the Scleral Spur were significantly higher after LPI (P Conclusions In patients with angle closure, changes in dynamic iridopupillary behavior are observed after LPI. The speed of pupillary constriction is faster after LPI.
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diagnostic performance of anterior chamber angle measurements for detecting eyes with narrow angles an anterior segment oct study
Archives of Ophthalmology, 2010Co-Authors: Arun Narayanaswamy, Tin Aung, Lisandro M Sakata, Raghavan Lavanya, David S Friedman, Paul J Foster, Mingguang He, Yiong Huak Chan, Mani BaskaranAbstract:Objective To assess the diagnostic performance of angle measurements from anterior segment optical coherence tomography (AS-OCT) images for identifying eyes with narrow angles. Methods We conducted a community-based cross-sectional study of individuals 50 years or older who had phakic eyes and who underwent AS-OCT imaging in the dark by a single operator and gonioscopy by an ophthalmologist masked to AS-OCT findings. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for at least 180° on gonioscopy. Horizontal AS-OCT images were analyzed for the following measurements using customized software: angle opening distance (AOD) at 250, 500, and 750 μm from the Scleral Spur; trabecular-iris space area (TISA) at 500 and 750 μm; and angle recess area (ARA) at 750 μm. Areas under the receiver operating characteristic curves (AUCs) were generated for AOD, TISA, and ARA to assess the performance of these measurements in detecting eyes with narrow angles. Results Of 2047 individuals examined, 582 were excluded mostly because of poor image quality or inability to locate the Scleral Spur. Of the remaining 1465 participants, 315 (21.5%) had narrow angles on gonioscopy. Mean (SD) age was 62.7 (7.7) years, 54.1% were women, and 90.0% were Chinese. The AUCs were highest for AOD750 in the nasal (0.90 [95% confidence interval, 0.89-0.92]) and temporal (0.91 [0.90-0.93]) quadrants. Conclusions The AOD750 is the most useful angle measurement for identifying individuals with gonioscopic narrow angles in gradable AS-OCT images. Poor definition of the Scleral Spur precludes quantitative analysis in approximately 25% of AS-OCT images.
David S Friedman - One of the best experts on this subject based on the ideXlab platform.
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Associations of iris structural measurements in a Chinese population: the Singapore Chinese Eye Study.
Investigative Ophthalmology & Visual Science, 2013Co-Authors: John Carson Allen, Carol Y. Cheung, David S Friedman, Mingguang He, Monisha E. Nongpiur, Yingfeng Zheng, Tien Yin Wong, Tin AungAbstract:PURPOSE: We determined the ocular biometric and demographic factors associated with iris parameters in Singaporean Chinese persons from a population-based sample. METHODS: Subjects were participants in the Singapore Chinese Eye Study, a population-based cross-sectional study of eye disease. Anterior segment optical coherence tomography images were analyzed using customized software to measure iris thickness at 750 μm from the Scleral Spur (IT750), iris area (I-Area), and iris curvature (I-Curv). Regression analyses were performed to assess the association between iris measurements with a range of demographic and ocular variables. The contribution of each independent variable to the iris parameter of interest was determined sequentially using a stepwise selection algorithm. RESULTS: We included 1473 participants with a mean age of 57.7 + 8.68 years, and 50.6% were men. The mean IT750, I-Area, and I-Curv were 0.46 ± 0.10 mm, 1.49 ± 0.24 mm(2), and 0.25 ± 0.13 mm, respectively. Statistical regression models, including a range of demographic and ocular parameters, explained 59.3%, 41.9%, and 34.3% of the variability in I-Curv, IT750, and I-Area, respectively. Angle opening distance at 750 μm from the Scleral Spur (AOD750) was the single factor associated most strongly with I-Curv, and explained 46.6% of its variation. CONCLUSIONS: A significant proportion of the variation in iris area, curvature, and thickness was not explained by other ocular and demographic parameters. Iris curvature was associated strongly with angle width, and of all parameters investigated, AOD750 was most highly correlated with iris curvature.
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assessment of trabecular meshwork width using swept source optical coherence tomography
Graefes Archive for Clinical and Experimental Ophthalmology, 2013Co-Authors: Mani Baskaran, Carol Y. Cheung, Lisandro M Sakata, David S Friedman, Ce Zheng, Shamira A. Perera, Anita S Chan, Tin AungAbstract:Purpose Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the Scleral Spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement.
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Analysis of Anterior Segment Dynamics Using Anterior Segment Optical Coherence Tomography Before and After Laser Peripheral Iridotomy
JAMA Ophthalmology, 2013Co-Authors: Ce Zheng, David S Friedman, Celeste P. Guzman, Carol Yim-lui Cheung, Yingke He, Arun Narayanaswamy, Paul T.k. Chew, Shamira A. Perera, Tin AungAbstract:Objective To evaluate changes in the speed of pupil constriction and in anterior segment parameters after laser peripheral iridotomy (LPI) in patients with angle closure using anterior segment optical coherence tomography. Methods In this prospective observational study, videos of pupil and anterior segment changes in response to illumination were captured with real-time video recording using anterior segment optical coherence tomography and were analyzed frame by frame before and after LPI. Customized software was used to measure the speed of pupil constriction and changes in anterior chamber depth and anterior chamber area, as well as iris thickness at 750 μm from the Scleral Spur, at the sphincter muscle region (0.75 mm from the pupillary margin), and at the mid-iris location (half the distance between the Scleral Spur and the pupillary margin). Pupil diameter, angle opening distance, and trabecular–iris space area at 500 μm from the Scleral Spur were determined. The speed of pupil constriction was defined as the rate of pupil diameter change in response to illumination. Results Twenty-nine patients were included. Most were Chinese (26 of 29 [90%]) and female (18 of 29 [62%]). The anterior chamber area, angle opening distance at 500 μm from the Scleral Spur, and trabecular–iris space area at 500 μm from the Scleral Spur were significantly higher after LPI (P Conclusions In patients with angle closure, changes in dynamic iridopupillary behavior are observed after LPI. The speed of pupillary constriction is faster after LPI.
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diagnostic performance of anterior chamber angle measurements for detecting eyes with narrow angles an anterior segment oct study
Archives of Ophthalmology, 2010Co-Authors: Arun Narayanaswamy, Tin Aung, Lisandro M Sakata, Raghavan Lavanya, David S Friedman, Paul J Foster, Mingguang He, Yiong Huak Chan, Mani BaskaranAbstract:Objective To assess the diagnostic performance of angle measurements from anterior segment optical coherence tomography (AS-OCT) images for identifying eyes with narrow angles. Methods We conducted a community-based cross-sectional study of individuals 50 years or older who had phakic eyes and who underwent AS-OCT imaging in the dark by a single operator and gonioscopy by an ophthalmologist masked to AS-OCT findings. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for at least 180° on gonioscopy. Horizontal AS-OCT images were analyzed for the following measurements using customized software: angle opening distance (AOD) at 250, 500, and 750 μm from the Scleral Spur; trabecular-iris space area (TISA) at 500 and 750 μm; and angle recess area (ARA) at 750 μm. Areas under the receiver operating characteristic curves (AUCs) were generated for AOD, TISA, and ARA to assess the performance of these measurements in detecting eyes with narrow angles. Results Of 2047 individuals examined, 582 were excluded mostly because of poor image quality or inability to locate the Scleral Spur. Of the remaining 1465 participants, 315 (21.5%) had narrow angles on gonioscopy. Mean (SD) age was 62.7 (7.7) years, 54.1% were women, and 90.0% were Chinese. The AUCs were highest for AOD750 in the nasal (0.90 [95% confidence interval, 0.89-0.92]) and temporal (0.91 [0.90-0.93]) quadrants. Conclusions The AOD750 is the most useful angle measurement for identifying individuals with gonioscopic narrow angles in gradable AS-OCT images. Poor definition of the Scleral Spur precludes quantitative analysis in approximately 25% of AS-OCT images.
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Changes in angle configuration after phacoemulsification measured by anterior segment optical coherence tomography.
Journal of Glaucoma, 2008Co-Authors: Winifred P. Nolan, Tin Aung, David S Friedman, Paul J Foster, Ce Zheng, Yiong Huak Chan, Scott D. Smith, David Huang, Paul T.k. ChewAbstract:Purpose: To measure changes in angle width after phacoemulsification and intraocular lens (IOL) implantation using anterior segment optical coherence tomography (AS-OCT). Materials and Methods: Twenty-one patients undergoing cataract surgery were recruited from the National University Hospital, Singapore. AS-OCT images were obtained of nasal and temporal angle quadrants before and at 1-month after surgery. Optical measurements of central anterior chamber depth were obtained, and gonioscopic measurement of angle width was recorded. AS-OCT angle width parameters measured in the nasal and temporal quadrants included the angle opening distance at 500mm (AOD500) anterior to the Scleral Spur and the trabecular iris surface area at 750mm (TISA750) anterior to the Scleral Spur. Preoperative and postoperative measurements were compared using paired samples t tests. Results: Data were collected from 21 eyes of 21 subjects with cataract. Seven subjects also had gonioscopic evidence of primary angle closure. Mean anterior chamber depth increased from 2.92 ( ± 0.54) to 4.24 ( ± 0.57) mm (P = 0.044) after cataract extraction. There was a significant increase in AS-OCT parameters for both nasal and temporal angles after surgery. An 88.2% increase in AOD500 was measured for the nasal angle quadrant with a mean difference of 213.9 ( ± 173)mm (P
Ernst R Tamm - One of the best experts on this subject based on the ideXlab platform.
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the trabecular meshwork outflow pathways structural and functional aspects
Experimental Eye Research, 2009Co-Authors: Ernst R TammAbstract:The major drainage structures for aqueous humor (AH) are the conventional or trabecular outflow pathways, which are comprised of the trabecular meshwork (made up by the uveal and corneoScleral meshworks), the juxtacanalicular connective tissue (JCT), the endothelial lining of Schlemm's canal (SC), the collecting channels and the aqueous veins. The trabecular meshwork (TM) outflow pathways are critical in providing resistance to AH outflow and in generating intraocular pressure (IOP). Outflow resistance in the TM outflow pathways increases with age and primary open-angle glaucoma. Uveal and corneoScleral meshworks form connective tissue lamellae or beams that are covered by flat TM cells which rest on a basal lamina. TM cells in the JCT are surrounded by fibrillar elements of the extracellular matrix (ECM) to form a loose connective tissue. In contrast to the other parts of the TM, JCT cells and ECM fibrils do not form lamellae, but are arranged more irregularly. SC inner wall endothelial cells form giant vacuoles in response to AH flow, as well as intracellular and paracellular pores. In addition, minipores that are covered with a diaphragm are observed. There is considerable evidence that normal AH outflow resistance resides in the inner wall region of SC, which is formed by the JCT and SC inner wall endothelium. Modulation of TM cell tone by the action of their actomyosin system affects TM outflow resistance. In addition, the architecture of the TM outflow pathways and consequently outflow resistance appear to be modulated by contraction of ciliary muscle and Scleral Spur cells. The Scleral Spur contains axons that innervate Scleral Spur cells or that have the ultrastructural characteristics of mechanosensory nerve endings.
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innervation of myofibroblast like Scleral Spur cells in human monkey eyes
Investigative Ophthalmology & Visual Science, 1995Co-Authors: Ernst R Tamm, F H Stefani, T A Koch, Bernd Mayer, Elke LutjendrecollAbstract:Purpose. To study the innervation of the presumably contractile, myofibroblast-like Scleral Spur cells in human and cynomolgus monkey eyes. Methods. Serial tangential sections of the Scleral Spur region of the eyes of 16 human donors and 6 cynomolgus monkeys were investigated with immunocytochemical methods. Antibodies against acetylcholinesterase, synaptophysin, α-smooth muscle actin, calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), nitric oxide synthase (NOS), substance P (SP), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP) were used. In addition, sections were processed for glyoxylic acid-induced catecholamine fluorescence (CF) and for NADPH-diaphorase (NADPH-d). Results. In the eyes of both species, circumferentially oriented varicose axons were observed in the Scleral Spur region of all quadrants. Double labeling showed that most of these Scleral Spur axons were in close contact with the α-smooth muscle actin-positive, myofibroblast-like Scleral Spur cells. In human eyes, the axons showed like-immunoreactivity (LI) for SP, CGRP, NPY, VIP, and NOS. In addition, numerous Scleral Spur axons stained for NADPH-d. Most SP-LI Scleral Spur axons were double-labeled for CGRP-LI, and none for VIP-LI. All NPY-LI Scleral Spur axons were double labeled for VIP-LI but lacked immunoreactivity to TH. Some VIP-LI axons were not labeled for NPY-LI. Nerve fibers immunoreactive (IR) for TH or positively stained for CF were not observed in association with Scleral Spur cells. In contrast, in cynomolgus monkey eyes, circumferentially oriented TH-IR and CF-positive varicose axons were observed frequently in the Scleral Spur region. In addition, SP-LI, CGRP-LI, and NPY-LI/TH-IR axons were present in the chamber angle of monkey eyes, whereas VIP-LI, VIP-LI/NPY-LI, NOS-positive, or NADPH-d-positive nerve fibers were absent. In both species, positive staining for acetylcholinesterase was seen only in the ciliary muscle, not in the Scleral Spur region. Conclusions. The close association of varicose axons with the myofibroblast-like Scleral Spur cells indicates that nervous signals modulate Scleral Spur cell tone. A sympathetic Scleral Spur cell innervation is present only in cynomolgus monkeys but seems to be absent in humans. Conversely, Scleral Spur axons of presumably parasympathetic origin (NOS-IR or NADPH-d-positive, VIP-LI, and VIP-LI/NPY-LI) are absent in the cynomolgus monkey but present in humans. In both species, a cholinergic innervation of the Scleral Spur cells seems to be rare or absent. Invest Ophthalmol Vis Sci. 1995 ;36 :1633-1644.
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nerve endings with structural characteristics of mechanoreceptors in the human Scleral Spur
Investigative Ophthalmology & Visual Science, 1994Co-Authors: Ernst R Tamm, Cassandra Flugel, F H Stefani, Elke LutjendrecollAbstract:Purpose. The innervation of the Scleral Spur region was investigated to learn whether mechanoreceptors are present in this region. Methods. Serial tangential sections and whole-mount preparations of the Scleral Spur region of 18 human eyes of different ages were investigated with electronmicroscopic and immunohistochemical methods. For immunohistochemistry antibodies against neurofilament-proteins, synaptophysin, substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), tyrosine-hydroxylase, dopamine-/3-hydroxylase, and acetylcholinesterase were used. Results. Club- or bulb-shaped nerve endings with a diameter of 5 /xm to 25 fim were identified in the Scleral Spur region throughout the whole circumference of the eyes. The terminals derive from myelinated axons with a diameter of approximately 3 ^m and stain with antibodies against neurofilament-proteins and synaptophysin but do not stain for tyrosine-hydroxylase, dopamine-j8-hydroxylase, acetylcholinesterase, NPY, VIP, SP, or CGRP. Electronmicroscopically, the endings contain abundant neurofilaments, granular and agranular vesicles of different sizes, numerous mitochondria, and lysosome-like lamellated structures. The endings are incompletely ensheathed by Schwann cells. Those areas of the cell membrane of the endings that are not covered by Schwann cells are in intimate contact with the fibrillar connective tissue elements of the Scleral Spur. Conclusion. These structural features are highly characteristic for mechanoreceptive nerve endings in other tissues of the human body. The authors therefore hypothesize that the clubor bulb-shaped nerve endings in the human Scleral Spur are afferent mechanoreceptors that measure stress or strain in the connective tissue elements of the Scleral Spur. Such changes might be induced by ciliary muscle contraction and/or by changes in intraocular pressure. Invest Ophthalmol Vis Sci. 1994; 35:1157-1166. A he inner layers of the mammalian eye are supplied by sensory nerves that originate from the trigeminal ganglion. The majority of these trigeminal fibers consist of unmyelinated fibers of the C-type. 1 " 4 Immuno
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immunocytochemical and ultrastructural studies of human Scleral Spur characterization of a contractile cell population
Ophthalmologe, 1993Co-Authors: Ernst R Tamm, Cassandra Flugel, F H Stefani, J W RohenAbstract:Contraction of the ciliary muscle induced by cholinergic drugs causes movement of the Scleral Spur and separation of the trabecular meshwork lamellae. The effect of epinephrine, however, does not seem to be mediated by ciliary muscle tone. We investigated the Scleral Spur in 37 human eyes (age 17-87 years). Serial tangential sections were studied with ultrastructural and immunocytochemical methods. The ciliary muscle cells do not enter the Scleral Spur, but their tendons, which consist of elastic fibers, are continuous with the elastic fibers in the Scleral Spur. Within the Scleral Spur is found a population of circularly oriented and spindle-shaped cells. The Scleral Spur cells form no bundles, but are loosely aggregated. They have long cytoplasmic processes and are connected to each other by adherence type and gap junctions. The Scleral Spur cells show intense staining for smooth-muscle-specific alpha-actin and myosin. Ultrastructurally, the Scleral Spur cells contain abundant actin filaments, but otherwise do not show the typical ultrastructure of ciliary muscle cells. The Scleral Spur cells do not express a complete basal lamina. They form individual tendinous connections with the elastic fibers in the Scleral Spur, which are continuous with the elastic fibers of the trabecular meshwork. The Scleral Spur cells are in close contact with nerve terminals containing small granular vesicles that are typical for adrenergic terminals. We conclude that the Scleral Spur cells are contractile myofibroblasts. Their contraction might be involved in the effects of epinephrine on the aqueous outflow.
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immunzytochemische und ultrastrukturelle untersuchungen am menschlichen skleralsporn charakterisierung einer kontraktilen zellpopulation immunocytochemical and ultrastructural studies of human Scleral Spur characterization of a contractile cell popul
1993Co-Authors: Ernst R Tamm, Cassandra Flugel, F H Stefani, J W RohenAbstract:Contraction of the ciliary muscle induced by cholinergic drugs causes movement of the Scleral Spur and separation of the trabecular meshwork lamellae. The effect of epinephrine, however, does not seem to be mediated by ciliary muscle tone. We investigated the Scleral Spur in 37 human eyes (age 17-87 years). Serial tangential sections were studied with ultrastructural and immunocytochemical methods. The ciliary muscle cells do not enter the Scleral Spur, but their tendons, which consist of elastic fibers, are continuous with the elastic fibers in the Scleral Spur. Within the Scleral Spur is found a population of circularly oriented and spindle-shaped cells. The Scleral Spur cells form no bundles, but are loosely aggregated. They have long cytoplasmic processes and are connected to each other by adherence type and gap junctions. The Scleral Spur cells show intense staining for smooth-muscle-specific alpha-actin and myosin. Ultrastructurally, the Scleral Spur cells contain abundant actin filaments, but otherwise do not show the typical ultrastructure of ciliary muscle cells. The Scleral Spur cells do not express a complete basal lamina. They form individual tendinous connections with the elastic fibers in the Scleral Spur, which are continuous with the elastic fibers of the trabecular meshwork. The Scleral Spur cells are in close contact with nerve terminals containing small granular vesicles that are typical for adrenergic terminals. We conclude that the Scleral Spur cells are contractile myofibroblasts. Their contraction might be involved in the effects of epinephrine on the aqueous outflow.
Elke Lutjendrecoll - One of the best experts on this subject based on the ideXlab platform.
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efferent and afferent innervation of primate trabecular meshwork and Scleral Spur
Investigative Ophthalmology & Visual Science, 2000Co-Authors: J M Selbach, Johannes Gottanka, M Wittmann, Elke LutjendrecollAbstract:PURPOSE. To determine the correlation between nerve terminals and cells or extracellular matrix (ECM) components in different portions of the primate trabecular meshwork (TM) and Scleral Spur (SS). METHODS. Serial sagittal and tangential sections through the anterior segments of 10 cynomolgus monkey eyes and 12 human eyes were investigated immunohistochemically with antibodies against the vesicular acetylcholine transporter (VACHT), vasoactive intestinal polypeptide (VIP), tyrosine-hydroxylase (TH), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), and galanin (GAL) and with a reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd) reaction. The distribution of the terminals was compared with that of α-smooth-muscle actin (SMA) staining in TM and SS. The relationship between terminals and adjacent cells or ECM components was also studied in ultrathin sections through the TM and SS of 11 monkey eyes cut in sagittal, tangential, and frontal planes. RESULTS. NADPHd-positive nerve terminals were present, especially in the outer portion of both human and monkey TM and in the SS. VACHT-immunoreactive (IR) fibers were found in human but not in monkey SS and TM. The fibers were most numerous in the elongated SS and posterior TM where most cells also stained for SMA. SP- and CGRP-IR nerve endings were also more numerous in the outer TM and SS than in the inner TM. Ultrastructurally, staining for SP was seen in nerve endings containing mitochondria and dense core vesicles and was in contact with the cribriform elastic network. In the posterior SS of monkey eyes were large terminals similar to those previously described in human eyes. CONCLUSIONS. The results show for the first time that in the primate TM and SS, there are cholinergic and nitrergic nerve terminals that could induce contraction and relaxation of TM and SS cells. Terminals in contact with the elastic-like network of the TM and containing SP-IR resemble afferent mechanoreceptor-like terminals in other parts of the body. These findings raise the possibility that the TM may have some ability to self-regulate aqueous humor outflow.
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classification of human Scleral Spur cells in monolayer culture
European Journal of Cell Biology, 1998Co-Authors: Ulrich Welgelusen, M Eichhorn, Hans Bloemendal, Elke LutjendrecollAbstract:Aqueous humor outflow in primate eyes can be facilitated by ciliary muscle contraction, thereby widening fluid pathways through the trabecular meshwork. Recently in the Scleral Spur smooth muscle (sm) α-actin positive myofibroblast-like cells have been described which are in contact with the elastic fiber system of both the Spur and trabecular meshwork. In the vicinity of these cells nerve terminals have been described. It is speculated that contraction of Scleral Spur cells can facilitate aqueous humor outflow, too. To provide a tool for further physiological and pharmacological studies monolayer cell cultures of human Scleral Spur have been established and characterized. For this purpose, cells derived from Scleral Spur, outer and inner trabecular meshwork and ciliary muscle tips from 7 donor eyes (43–87 years-old respectively, obtained 3–7h post mortem) were grown in tissue culture medium and the different monolayer cells classified by their growth characteristics, and by immunohistochemical staining for vimentin, α-sm-actin, desmin, and αB-crystallin, respectively. In addition, the presence of αB-crystallin mRNA and desmin mRNA was verified using the polymerase chain reaction (PCR)-method. We were able to characterize and distinguish human Scleral Spur cells from adjacent ciliary muscle and trabecular meshwork cells. Scleral Spur cells (SPC) grew slower than ciliary muscle cells (CMC) but much faster than trabecular meshwork cells (TMC). All cells showed the same staining characteristics in vitro as they did in vivo. Scleral Spur cells stained for vimentin and α-sm-actin, but not for desmin and αB-crystallin. The corresponding mRNAs of the latter two proteins could not be detected by PCR in the Spur cells. Cells grew out from all donor eyes so that they actually provide a tool for further experimental studies.
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innervation of myofibroblast like Scleral Spur cells in human monkey eyes
Investigative Ophthalmology & Visual Science, 1995Co-Authors: Ernst R Tamm, F H Stefani, T A Koch, Bernd Mayer, Elke LutjendrecollAbstract:Purpose. To study the innervation of the presumably contractile, myofibroblast-like Scleral Spur cells in human and cynomolgus monkey eyes. Methods. Serial tangential sections of the Scleral Spur region of the eyes of 16 human donors and 6 cynomolgus monkeys were investigated with immunocytochemical methods. Antibodies against acetylcholinesterase, synaptophysin, α-smooth muscle actin, calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), nitric oxide synthase (NOS), substance P (SP), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP) were used. In addition, sections were processed for glyoxylic acid-induced catecholamine fluorescence (CF) and for NADPH-diaphorase (NADPH-d). Results. In the eyes of both species, circumferentially oriented varicose axons were observed in the Scleral Spur region of all quadrants. Double labeling showed that most of these Scleral Spur axons were in close contact with the α-smooth muscle actin-positive, myofibroblast-like Scleral Spur cells. In human eyes, the axons showed like-immunoreactivity (LI) for SP, CGRP, NPY, VIP, and NOS. In addition, numerous Scleral Spur axons stained for NADPH-d. Most SP-LI Scleral Spur axons were double-labeled for CGRP-LI, and none for VIP-LI. All NPY-LI Scleral Spur axons were double labeled for VIP-LI but lacked immunoreactivity to TH. Some VIP-LI axons were not labeled for NPY-LI. Nerve fibers immunoreactive (IR) for TH or positively stained for CF were not observed in association with Scleral Spur cells. In contrast, in cynomolgus monkey eyes, circumferentially oriented TH-IR and CF-positive varicose axons were observed frequently in the Scleral Spur region. In addition, SP-LI, CGRP-LI, and NPY-LI/TH-IR axons were present in the chamber angle of monkey eyes, whereas VIP-LI, VIP-LI/NPY-LI, NOS-positive, or NADPH-d-positive nerve fibers were absent. In both species, positive staining for acetylcholinesterase was seen only in the ciliary muscle, not in the Scleral Spur region. Conclusions. The close association of varicose axons with the myofibroblast-like Scleral Spur cells indicates that nervous signals modulate Scleral Spur cell tone. A sympathetic Scleral Spur cell innervation is present only in cynomolgus monkeys but seems to be absent in humans. Conversely, Scleral Spur axons of presumably parasympathetic origin (NOS-IR or NADPH-d-positive, VIP-LI, and VIP-LI/NPY-LI) are absent in the cynomolgus monkey but present in humans. In both species, a cholinergic innervation of the Scleral Spur cells seems to be rare or absent. Invest Ophthalmol Vis Sci. 1995 ;36 :1633-1644.
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nerve endings with structural characteristics of mechanoreceptors in the human Scleral Spur
Investigative Ophthalmology & Visual Science, 1994Co-Authors: Ernst R Tamm, Cassandra Flugel, F H Stefani, Elke LutjendrecollAbstract:Purpose. The innervation of the Scleral Spur region was investigated to learn whether mechanoreceptors are present in this region. Methods. Serial tangential sections and whole-mount preparations of the Scleral Spur region of 18 human eyes of different ages were investigated with electronmicroscopic and immunohistochemical methods. For immunohistochemistry antibodies against neurofilament-proteins, synaptophysin, substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), tyrosine-hydroxylase, dopamine-/3-hydroxylase, and acetylcholinesterase were used. Results. Club- or bulb-shaped nerve endings with a diameter of 5 /xm to 25 fim were identified in the Scleral Spur region throughout the whole circumference of the eyes. The terminals derive from myelinated axons with a diameter of approximately 3 ^m and stain with antibodies against neurofilament-proteins and synaptophysin but do not stain for tyrosine-hydroxylase, dopamine-j8-hydroxylase, acetylcholinesterase, NPY, VIP, SP, or CGRP. Electronmicroscopically, the endings contain abundant neurofilaments, granular and agranular vesicles of different sizes, numerous mitochondria, and lysosome-like lamellated structures. The endings are incompletely ensheathed by Schwann cells. Those areas of the cell membrane of the endings that are not covered by Schwann cells are in intimate contact with the fibrillar connective tissue elements of the Scleral Spur. Conclusion. These structural features are highly characteristic for mechanoreceptive nerve endings in other tissues of the human body. The authors therefore hypothesize that the clubor bulb-shaped nerve endings in the human Scleral Spur are afferent mechanoreceptors that measure stress or strain in the connective tissue elements of the Scleral Spur. Such changes might be induced by ciliary muscle contraction and/or by changes in intraocular pressure. Invest Ophthalmol Vis Sci. 1994; 35:1157-1166. A he inner layers of the mammalian eye are supplied by sensory nerves that originate from the trigeminal ganglion. The majority of these trigeminal fibers consist of unmyelinated fibers of the C-type. 1 " 4 Immuno
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assessment of trabecular meshwork width using swept source optical coherence tomography
Graefes Archive for Clinical and Experimental Ophthalmology, 2013Co-Authors: Mani Baskaran, Carol Y. Cheung, Lisandro M Sakata, David S Friedman, Ce Zheng, Shamira A. Perera, Anita S Chan, Tin AungAbstract:Purpose Measurements of the angle width by ultrasound biomicroscopy or anterior segment optical coherence tomography are usually performed 500 μm from the Scleral Spur, as the anterior part of trabecular meshwork (TM) is assumed to lie within this distance. The aim of this study was to measure TM width using swept source optical coherence tomography (SS-OCT, CASIA SS-1000, Tomey Corporation, Nagoya, Japan), and to investigate factors influencing this measurement.
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diagnostic performance of anterior chamber angle measurements for detecting eyes with narrow angles an anterior segment oct study
Archives of Ophthalmology, 2010Co-Authors: Arun Narayanaswamy, Tin Aung, Lisandro M Sakata, Raghavan Lavanya, David S Friedman, Paul J Foster, Mingguang He, Yiong Huak Chan, Mani BaskaranAbstract:Objective To assess the diagnostic performance of angle measurements from anterior segment optical coherence tomography (AS-OCT) images for identifying eyes with narrow angles. Methods We conducted a community-based cross-sectional study of individuals 50 years or older who had phakic eyes and who underwent AS-OCT imaging in the dark by a single operator and gonioscopy by an ophthalmologist masked to AS-OCT findings. An eye was considered to have narrow angles if the posterior pigmented trabecular meshwork was not visible for at least 180° on gonioscopy. Horizontal AS-OCT images were analyzed for the following measurements using customized software: angle opening distance (AOD) at 250, 500, and 750 μm from the Scleral Spur; trabecular-iris space area (TISA) at 500 and 750 μm; and angle recess area (ARA) at 750 μm. Areas under the receiver operating characteristic curves (AUCs) were generated for AOD, TISA, and ARA to assess the performance of these measurements in detecting eyes with narrow angles. Results Of 2047 individuals examined, 582 were excluded mostly because of poor image quality or inability to locate the Scleral Spur. Of the remaining 1465 participants, 315 (21.5%) had narrow angles on gonioscopy. Mean (SD) age was 62.7 (7.7) years, 54.1% were women, and 90.0% were Chinese. The AUCs were highest for AOD750 in the nasal (0.90 [95% confidence interval, 0.89-0.92]) and temporal (0.91 [0.90-0.93]) quadrants. Conclusions The AOD750 is the most useful angle measurement for identifying individuals with gonioscopic narrow angles in gradable AS-OCT images. Poor definition of the Scleral Spur precludes quantitative analysis in approximately 25% of AS-OCT images.
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Quantitative analysis of anterior segment optical coherence tomography images: the Zhongshan Angle Assessment Program
British Journal of Ophthalmology, 2008Co-Authors: James W Console, Tin Aung, Lisandro M Sakata, David S Friedman, Mingguang HeAbstract:Aim: To describe a new image analysis method and software for anterior chamber images obtained by the anterior-segment optical coherence tomography (AS-OCT) and to assess its intraobserver and interobserver measurement reproducibility. Methods: Twenty 8-bit greyscale 600×300 AS-OCT images with apparent wide angles and 20 images with apparent narrow angles were consecutively selected from a database. Two glaucoma fellowship-trained ophthalmologists used proprietary image analysis software to analyse the images twice. Algorithms defined the borders and curvatures of anterior chamber (AC) structures and measured AC parameters using Scleral Spur location as the only observer input. The intraobserver and interobserver reproducibility of Scleral Spur location and angle parameters was calculated in terms of limits of agreement (LOA; mean of differences±1.96SD of differences) and coefficient of variation (CV; SD of differences/overall mean). Results: The analysis software successfully measured all parameters in all images. When the same image was assessed twice by the same grader, the mean differences ranged from 0 to 0.010 mm in linear measurements and 0.001 to 0.006 mm2 in angle area measurements. LOA tended to be greater in the wider angles. The upper and lower limit values of LOAs were approximately 1/5 to 1/4 of the overall mean. Measurements between two graders had a higher variance. Reproducibility in terms of CV was better in wide angles when compared with narrow angles. The reproducibility of Scleral Spur placement between observers was poorer in narrow angles (p = 0.001). About 50% of the interobserver variance in angle-area measurements was attributable to the variance of Scleral Spur placement, while this proportion was only 10–20% in linear measurements. Conclusions: Determination of angle parameters using semiautomated software leads to variability in measurement. Variability increases when more than one observer identifies the Scleral Spur. Variability differs in narrow and open angles, and so including both types is essential when evaluating angle-assessment software. A fully automated analysis and higher image resolution would likely improve quantification of Visante AS-OCT images.
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assessment of the Scleral Spur in anterior segment optical coherence tomography images
Archives of Ophthalmology, 2008Co-Authors: Lisandro M Sakata, Raghavan Lavanya, David S Friedman, Han T Aung, S K L Seah, Paul J Foster, Tin AungAbstract:Objective To assess visibility of the Scleral Spur in anterior segment optical coherence tomography (AS-OCT) images. Methods This cross-sectional observational study included 502 participants aged 50 years or older who had no previous ophthalmic problems and were recruited from a community clinic in Singapore. All participants underwent gonioscopy and AS-OCT (Visante; Carl Zeiss Meditec, Dublin, California). Scleral Spur location was assessed in AS-OCT images by 2 examiners with glaucoma subspecialty training and was defined as the point where there was an inward protrusion of the sclera with a change in curvature of its inner surface. Results Scleral Spur location could be determined in 72% of the images of the right eye. Its location on AS-OCT images was less detectable in quadrants with a closed angle on gonioscopy and also in images obtained in the superior and inferior compared with the nasal and temporal quadrants (64%, 67%, 75%, and 80%, respectively; P Conclusions The inability to detect the Scleral Spur may hamper quantitative analysis of anterior chamber angle parameters that are dependent on the location of this anatomical structure, particularly in the superior and inferior quadrants. New parameters independent of the Scleral Spur may be useful for detecting eyes at risk of angle closure.