The Experts below are selected from a list of 110838 Experts worldwide ranked by ideXlab platform
Linda M Zangwill - One of the best experts on this subject based on the ideXlab platform.
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a mathematical description of Nerve Fiber bundle trajectories and their variability in the human retina
Vision Research, 2009Co-Authors: Nomdo M Jansonius, P. J. Airaksinen, Linda M Zangwill, Pamela A Sample, J Nevalainen, B Selig, W M Budde, J B Jonas, Wolf A Lagreze, Reinhard VontheinAbstract:We developed a mathematical model wherein retinal Nerve Fiber trajectories can be described and the corresponding inter-subject variability analyzed. The model was based on traced Nerve Fiber bundle trajectories extracted from 55 fundus photographs of 55 human subjects. The model resembled the typical retinal Nerve Fiber layer course within 20 degrees eccentricity. Depending on the location of the visual field test point, the standard deviation of the calculated corresponding angular location at the optic Nerve head circumference ranged from less than 1 degrees to 18 degrees , with an average of 8.8 degrees .
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retinal Nerve Fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes
Ophthalmology, 2003Co-Authors: Tarek El A Beltagi, Linda M Zangwill, Pamela A Sample, Christopher Bowd, Catherine Boden, Payarn Amini, Robert N WeinrebAbstract:Abstract Purpose To determine the relationship between areas of glaucomatous retinal Nerve Fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Design Retrospective observational case series. Partcipants Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >−8 dB were included. Methods Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. Main outcome measures The location and number of optical coherence tomography clock hour retinal Nerve Fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography–measured retinal Nerve Fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression ( R 2 ). Results The retinal Nerve Fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results ( R 2 ) showed that deviation from the normal retinal Nerve Fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions ( R 2 range, 0.34–0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region ( R 2 = 0.01). Conclusions Localized retinal Nerve Fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.
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association between quantitative Nerve Fiber layer measurement and visual field loss in glaucoma
American Journal of Ophthalmology, 1995Co-Authors: Robert N Weinreb, Sima Shakiba, Pamela A Sample, Shah In Shahrokni, Stewart Van Horn, Valerie Garden, Somkiat Asawaphureekorn, Linda M ZangwillAbstract:Purpose To evaluate the association between quantitative Nerve Fiber layer measurements and visual field loss in patients with primary open-angle glaucoma. Methods Quantitative retinal Nerve Fiber layer measurements were obtained in 53 patients with primary open-angle glaucoma by using confocal scanning laser ophthalmoscopy (cross-section area) and confocal scanning laser polarimetry (retardation ratio). For each eye, three images were obtained with each instrument. An image that was the mean of those three was created and used in all analyses. We investigated the association between global, regional, and hemifield differences in retinal Nerve Fiber layer measurements and visual field loss with linear regression techniques. Results The retardation ratio decreased with increasing mean visual field loss, measured both globally and regionally; R2 (the amount of variation explained by the model) ranged from 8% to 21%. Retinal Nerve Fiber layer cross-section area was not significantly associated with global measures of visual field loss. The inferior visual field mean deviation increased with decreasing superior retinal Nerve Fiber layer cross-section area (R2 = 8.2%, P = .04); superior visual field mean deviation was not associated with inferior retinal Nerve Fiber layer cross-section area (R2 = 2.6%, P = .25). Hemifield differences in visual field mean deviation increased with increasing hemifield differences in retinal Nerve Fiber layer cross-section area (R2 = 20.0%, P Conclusions Quantitative measures of the retinal Nerve Fiber layer using both confocal scanning laser ophthalmoscopy and confocal scanning laser polarimetry were correlated with visual field loss in glaucoma patients.
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scanning laser polarimetry to measure the Nerve Fiber layer of normal and glaucomatous eyes
American Journal of Ophthalmology, 1995Co-Authors: Robert N Weinreb, Sima Shakiba, Linda M ZangwillAbstract:Purpose To determine whether retardation (change in polarization) measurements of healthy subjects and glaucoma patients obtained by using a confocal scanning laser polarimeter correspond to known properties of the Nerve Fiber layer. Methods A polarimeter, an optical device used to measure the change in linear polarization of light (retardation), was interfaced with a scanning laser ophthalmoscope to obtain retardation data at 65,536 locations (256 × 256 pixels) in a study of normal subjects and patients with primary open-angle glaucoma. To validate the instrument, we compared our measurements with known properties of the human retinal Nerve Fiber layer in 105 normal subjects. Additionally, we compared retardation measurements in eyes of 64 normal subjects and 64 age-matched glaucoma patients treated in a referral practice. Results In normal eyes, mean (± S.D.) peripapillary retardation was highest in the superior and inferior arcuate regions and lowest in the temporal and nasal regions, 12.0 ± 1.9, 13.1 ± 2.0, 7.0 ± 1.8, and 7.0 ± 1.6 degrees, respectively. Retardation decreased toward the periphery and was lower over blood vessels. In normal eyes, retardation decreased with increasing age in the superior and inferior regions. Mean retardation was statistically significantly higher among normal eyes than glaucoma eyes in the inferior and superior regions but not in the temporal or nasal areas. Conclusions Scanning laser polarimetry provides quantitative measurements that correspond to known properties of the retinal Nerve Fiber layer in normal and glaucomatous eyes.
Robert N Weinreb - One of the best experts on this subject based on the ideXlab platform.
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retinal Nerve Fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes
Ophthalmology, 2003Co-Authors: Tarek El A Beltagi, Linda M Zangwill, Pamela A Sample, Christopher Bowd, Catherine Boden, Payarn Amini, Robert N WeinrebAbstract:Abstract Purpose To determine the relationship between areas of glaucomatous retinal Nerve Fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Design Retrospective observational case series. Partcipants Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >−8 dB were included. Methods Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. Main outcome measures The location and number of optical coherence tomography clock hour retinal Nerve Fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography–measured retinal Nerve Fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression ( R 2 ). Results The retinal Nerve Fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results ( R 2 ) showed that deviation from the normal retinal Nerve Fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions ( R 2 range, 0.34–0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region ( R 2 = 0.01). Conclusions Localized retinal Nerve Fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.
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association between quantitative Nerve Fiber layer measurement and visual field loss in glaucoma
American Journal of Ophthalmology, 1995Co-Authors: Robert N Weinreb, Sima Shakiba, Pamela A Sample, Shah In Shahrokni, Stewart Van Horn, Valerie Garden, Somkiat Asawaphureekorn, Linda M ZangwillAbstract:Purpose To evaluate the association between quantitative Nerve Fiber layer measurements and visual field loss in patients with primary open-angle glaucoma. Methods Quantitative retinal Nerve Fiber layer measurements were obtained in 53 patients with primary open-angle glaucoma by using confocal scanning laser ophthalmoscopy (cross-section area) and confocal scanning laser polarimetry (retardation ratio). For each eye, three images were obtained with each instrument. An image that was the mean of those three was created and used in all analyses. We investigated the association between global, regional, and hemifield differences in retinal Nerve Fiber layer measurements and visual field loss with linear regression techniques. Results The retardation ratio decreased with increasing mean visual field loss, measured both globally and regionally; R2 (the amount of variation explained by the model) ranged from 8% to 21%. Retinal Nerve Fiber layer cross-section area was not significantly associated with global measures of visual field loss. The inferior visual field mean deviation increased with decreasing superior retinal Nerve Fiber layer cross-section area (R2 = 8.2%, P = .04); superior visual field mean deviation was not associated with inferior retinal Nerve Fiber layer cross-section area (R2 = 2.6%, P = .25). Hemifield differences in visual field mean deviation increased with increasing hemifield differences in retinal Nerve Fiber layer cross-section area (R2 = 20.0%, P Conclusions Quantitative measures of the retinal Nerve Fiber layer using both confocal scanning laser ophthalmoscopy and confocal scanning laser polarimetry were correlated with visual field loss in glaucoma patients.
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scanning laser polarimetry to measure the Nerve Fiber layer of normal and glaucomatous eyes
American Journal of Ophthalmology, 1995Co-Authors: Robert N Weinreb, Sima Shakiba, Linda M ZangwillAbstract:Purpose To determine whether retardation (change in polarization) measurements of healthy subjects and glaucoma patients obtained by using a confocal scanning laser polarimeter correspond to known properties of the Nerve Fiber layer. Methods A polarimeter, an optical device used to measure the change in linear polarization of light (retardation), was interfaced with a scanning laser ophthalmoscope to obtain retardation data at 65,536 locations (256 × 256 pixels) in a study of normal subjects and patients with primary open-angle glaucoma. To validate the instrument, we compared our measurements with known properties of the human retinal Nerve Fiber layer in 105 normal subjects. Additionally, we compared retardation measurements in eyes of 64 normal subjects and 64 age-matched glaucoma patients treated in a referral practice. Results In normal eyes, mean (± S.D.) peripapillary retardation was highest in the superior and inferior arcuate regions and lowest in the temporal and nasal regions, 12.0 ± 1.9, 13.1 ± 2.0, 7.0 ± 1.8, and 7.0 ± 1.6 degrees, respectively. Retardation decreased toward the periphery and was lower over blood vessels. In normal eyes, retardation decreased with increasing age in the superior and inferior regions. Mean retardation was statistically significantly higher among normal eyes than glaucoma eyes in the inferior and superior regions but not in the temporal or nasal areas. Conclusions Scanning laser polarimetry provides quantitative measurements that correspond to known properties of the retinal Nerve Fiber layer in normal and glaucomatous eyes.
Ralf P Tornow - One of the best experts on this subject based on the ideXlab platform.
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retinal Nerve Fiber layer thickness in normals measured by spectral domain oct
Journal of Glaucoma, 2010Co-Authors: Delia Bendschneider, Ralf P Tornow, Folkert K Horn, Robert Laemmer, Christopher W Roessler, Anselm G M Juenemann, Friedrich E Kruse, Christian Y MardinAbstract:PurposeTo determine normal values for peripapillary retinal Nerve Fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables.Patients and MethodsThe peripapillar
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correlation between local glaucomatous visual field defects and loss of Nerve Fiber layer thickness measured with polarimetry and spectral domain oct
Investigative Ophthalmology & Visual Science, 2009Co-Authors: Folkert K Horn, Robert Laemmer, Anselm G M Juenemann, Friedrich E Kruse, Christian Y Mardin, D Baleanu, Ralf P TornowAbstract:PURPOSE: To study the correlation between local perimetric field defects and glaucoma-induced thickness reduction of the Nerve layer measured in the peripapillary area with scanning laser polarimetry (SLP) and spectral domain optical coherence tomography (SOCT) and to compare the results with those of a theoretical model. METHODS: The thickness of the retinal Nerve Fiber layer was determined in 32 sectors (11.25 degrees each) by using SLP with variable cornea compensation (GDxVCC; Laser Diagnostics, San Diego, CA) and the newly introduced high-resolution SOCT (Spectralis; Heidelberg Engineering, Heidelberg, Germany). Eighty-eight healthy subjects served as control subjects, to determine the thickness deviation in patients with glaucoma. The relationship between glaucomatous Nerve Fiber reduction and visual field losses was calculated in six Nerve Fiber bundle-related areas. Sixty-four patients at different stages of open-angle glaucoma and 26 patients with ocular hypertension underwent perimetry (Octopus G1; Haag-Streit, Koniz, Switzerland) and measurements with the two morphometric techniques. RESULTS: Sector-shaped analyses between local perimetric losses and reduction of the retinal Nerve Fiber layer thickness showed a significant association for corresponding areas except for the central visual field in SLP. Correlation coefficients were highest in the area of the nasal inferior visual field (SOCT, -0.81; SLP, -0.57). A linear model describes the association between structural and functional damage. CONCLUSIONS: Localized perimetric defects can be explained by reduced Nerve Fiber layer thickness. The data indicate that the present SOCT is useful for determining the functional-structural relationship in peripapillary areas and that association between perimetric defects and corresponding Nerve Fiber losses is stronger for SOCT than for the present SLP. (ClinicalTrials.gov number, NCT00494923.).
Peter Novak - One of the best experts on this subject based on the ideXlab platform.
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Electrochemical Skin Conductance Correlates with Skin Nerve Fiber Density.
Frontiers in aging neuroscience, 2016Co-Authors: Peter NovakAbstract:Purpose: Electrochemical skin conductance (ESC) using reverse iontophoresis and chronoamperometry has been used to evaluate abnormal function of small Fibers. How ESC correlates with loss of small Fibers in skin is unclear. Methods: This was a prospective, blinded study. The primary outcome measure was the correlation between ESC at the feet and results of skin biopsies including epidermal Nerve Fiber density (ENFD) and sweat gland Nerve Fiber density (SGNFD) at the distal leg. ESC, ENFD and SGNFD data were normalized by adjusting for weight. The secondary outcome measures were the correlation between ESC and the following variables: quantitative sudomotor axon reflex test (QSART) and symptom scales (neuropathy, pain and autonomic). Results: 81 patients ((mean±sd): age=53.3±17.3, men/women=25/56 were enrolled in the study. ESC was reduced in subjects with abnormally low ENFD (ENFD normal/abnormal, ESC = 1.17±0.27/0.87±0.34 µSiemens/kg, p
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electrochemical skin conductance correlates with skin Nerve Fiber density
Frontiers in Aging Neuroscience, 2016Co-Authors: Peter NovakAbstract:Purpose: Electrochemical skin conductance (ESC) using reverse iontophoresis and chronoamperometry has been used to evaluate abnormal function of small Fibers. How ESC correlates with loss of small Fibers in skin is unclear. Methods: This was a prospective, blinded study. The primary outcome measure was the correlation between ESC at the feet and results of skin biopsies including epidermal Nerve Fiber density (ENFD) and sweat gland Nerve Fiber density (SGNFD) at the distal leg. ESC, ENFD and SGNFD data were normalized by adjusting for weight. The secondary outcome measures were the correlation between ESC and the following variables: quantitative sudomotor axon reflex test (QSART) and symptom scales (neuropathy, pain and autonomic). Results: 81 patients ((mean±sd): age=53.3±17.3, men/women=25/56 were enrolled in the study. ESC was reduced in subjects with abnormally low ENFD (ENFD normal/abnormal, ESC = 1.17±0.27/0.87±0.34 µSiemens/kg, p<0.0008) and abnormally low SGNFD (SGNFD normal/abnormal ESC=1.09±0.34/,0.78±0.3 µSiemens/kg,p<0.0003). ESC correlated with ENFD (ρ=0.73, p=0.0001) and SGNFD (ρ=0.64, p=0.0001). ESC did not correlate with symptom scales. Conclusion: ESC is diminished in subjects who have a reduced number of small Fibers in the skin and the ESC reduction is proportional to ENFD and SGNFD. ESC can be useful in detecting loss of small Nerve Fibers.
Christian Y Mardin - One of the best experts on this subject based on the ideXlab platform.
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retinal Nerve Fiber layer thickness in normals measured by spectral domain oct
Journal of Glaucoma, 2010Co-Authors: Delia Bendschneider, Ralf P Tornow, Folkert K Horn, Robert Laemmer, Christopher W Roessler, Anselm G M Juenemann, Friedrich E Kruse, Christian Y MardinAbstract:PurposeTo determine normal values for peripapillary retinal Nerve Fiber layer thickness (RNFL) measured by spectral domain Optical Coherence Tomography (SOCT) in healthy white adults and to examine the relationship of RNFL with age, gender, and clinical variables.Patients and MethodsThe peripapillar
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correlation between local glaucomatous visual field defects and loss of Nerve Fiber layer thickness measured with polarimetry and spectral domain oct
Investigative Ophthalmology & Visual Science, 2009Co-Authors: Folkert K Horn, Robert Laemmer, Anselm G M Juenemann, Friedrich E Kruse, Christian Y Mardin, D Baleanu, Ralf P TornowAbstract:PURPOSE: To study the correlation between local perimetric field defects and glaucoma-induced thickness reduction of the Nerve layer measured in the peripapillary area with scanning laser polarimetry (SLP) and spectral domain optical coherence tomography (SOCT) and to compare the results with those of a theoretical model. METHODS: The thickness of the retinal Nerve Fiber layer was determined in 32 sectors (11.25 degrees each) by using SLP with variable cornea compensation (GDxVCC; Laser Diagnostics, San Diego, CA) and the newly introduced high-resolution SOCT (Spectralis; Heidelberg Engineering, Heidelberg, Germany). Eighty-eight healthy subjects served as control subjects, to determine the thickness deviation in patients with glaucoma. The relationship between glaucomatous Nerve Fiber reduction and visual field losses was calculated in six Nerve Fiber bundle-related areas. Sixty-four patients at different stages of open-angle glaucoma and 26 patients with ocular hypertension underwent perimetry (Octopus G1; Haag-Streit, Koniz, Switzerland) and measurements with the two morphometric techniques. RESULTS: Sector-shaped analyses between local perimetric losses and reduction of the retinal Nerve Fiber layer thickness showed a significant association for corresponding areas except for the central visual field in SLP. Correlation coefficients were highest in the area of the nasal inferior visual field (SOCT, -0.81; SLP, -0.57). A linear model describes the association between structural and functional damage. CONCLUSIONS: Localized perimetric defects can be explained by reduced Nerve Fiber layer thickness. The data indicate that the present SOCT is useful for determining the functional-structural relationship in peripapillary areas and that association between perimetric defects and corresponding Nerve Fiber losses is stronger for SOCT than for the present SLP. (ClinicalTrials.gov number, NCT00494923.).
