The Experts below are selected from a list of 6378 Experts worldwide ranked by ideXlab platform
William J Dupps - One of the best experts on this subject based on the ideXlab platform.
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discriminant value of Custom ocular response analyzer waveform derivatives in keratoconus
Ophthalmology, 2014Co-Authors: Katie M Hallahan, Abhijit Sinha Roy, Renato Ambrosio, Marcella Q Salomao, William J DuppsAbstract:Purpose To evaluate the performance of corneal hysteresis (CH), corneal resistance factor, and 16 investigator-derived Ocular Response Analyzer (ORA) Variables in distinguishing keratoconus (KC) from the nondiseased state. Design Retrospective case series. Participants Fifty-four eyes of 27 unaffected patients and 49 eyes of 25 KC patients from the Instituto de Olhos, Rio de Janeiro, Brazil. Methods Sixteen candidate Variables were derived from exported ORA signals to characterize putative indicators of biomechanical behavior. Area under the receiver operating characteristic curve (AUC) and the Z statistic were used to compare diagnostic performance. Main Outcome Measures Discriminant value of standard and derived ORA Variables as measured by AUC. Results Fifteen of 16 candidate Variables performed significantly better than chance (AUC, >0.5) at discriminating KC. Diagnostic performance was greatest for a Custom Variable related to the depth of deformation as defined by the minimum applanation signal intensity during corneal deformation (concavity min ; mean AUC ± standard error, 0.985±0.002) and a new measure incorporating the pressure-deformation relationship of the entire response cycle (hysteresis loop area, 0.967±0.002). Z statistics assessing the discriminative value of each of the top 5 Variables demonstrated superiority to CH (AUC, 0.862±0.002). Concavity min had the best overall predictive accuracy (cutoff value, 50.37; 94.9% sensitivity, 91.7% specificity, and 93.2% test accuracy), and the top 4 Variables demonstrated the most consistent relationships to KC severity. Conclusions Investigator-derived ORA Variables related to the depth of deformation and the pressure-deformation relationship demonstrated very high test accuracy for detecting the presence of KC. Beyond their diagnostic value, the candidate Variables described in this report provide mechanistic insight into the nature of the ORA signal and the characteristic changes in corneal dynamics associated with KC.
Elliott J. Rouse - One of the best experts on this subject based on the ideXlab platform.
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Understanding patient preference in prosthetic ankle stiffness
'Springer Science and Business Media LLC', 2021Co-Authors: Tyler R. Clites, Max K Shepherd, Kimberly A. Ingraham, Leslie Wontorcik, Elliott J. RouseAbstract:Abstract Background User preference has the potential to facilitate the design, control, and prescription of prostheses, but we do not yet understand which physiological factors drive preference, or if preference is associated with clinical benefits. Methods Subjects with unilateral below-knee amputation walked on a Custom Variable-stiffness prosthetic ankle and manipulated a dial to determine their preferred prosthetic ankle stiffness at three walking speeds. We evaluated anthropomorphic, metabolic, biomechanical, and performance-based descriptors at stiffness levels surrounding each subject’s preferred stiffness. Results Subjects preferred lower stiffness values at their self-selected treadmill walking speed, and elected to walk faster overground with ankle stiffness at or above their preferred stiffness. Preferred stiffness maximized the kinematic symmetry between prosthetic and unaffected joints, but was not significantly correlated with body mass or metabolic rate. Conclusion These results imply that some physiological factors are weighted more heavily when determining preferred stiffness, and that preference may be associated with clinically relevant improvements in gait
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the difference threshold of ankle foot prosthesis stiffness for persons with transtibial amputation
IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018Co-Authors: Max K Shepherd, Alejandro F Azocar, Matthew J Major, Elliott J. RouseAbstract:Most prosthetic feet behave like springs, and their stiffness affects many important facets of amputee gait. Despite the importance of prosthesis stiffness, the ability of amputees to sense stiffness changes-that is, distinguish between more or less stiff feet-is unknown. This perceptual resolution has implications for the methodology and overall significance of selecting the optimal foot stiffness during prescription. In this experiment, we used a Custom, Variable-stiffness ankle prosthesis to make small adjustments to stiffness in between steps, and below-knee amputees were asked to identify whether the ankle became more or less stiff. We determined that the average difference threshold of stiffness was 8%, meaning that subjects could correctly identify an 8% change in stiffness 75% of the time. This high sensitivity underscores the importance of optimizing prosthesis stiffness on an individual basis, and suggests a shift is needed in the characterization of commercial feet and the use of stiffness variation during the prescription process.
Max K Shepherd - One of the best experts on this subject based on the ideXlab platform.
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Understanding patient preference in prosthetic ankle stiffness
'Springer Science and Business Media LLC', 2021Co-Authors: Tyler R. Clites, Max K Shepherd, Kimberly A. Ingraham, Leslie Wontorcik, Elliott J. RouseAbstract:Abstract Background User preference has the potential to facilitate the design, control, and prescription of prostheses, but we do not yet understand which physiological factors drive preference, or if preference is associated with clinical benefits. Methods Subjects with unilateral below-knee amputation walked on a Custom Variable-stiffness prosthetic ankle and manipulated a dial to determine their preferred prosthetic ankle stiffness at three walking speeds. We evaluated anthropomorphic, metabolic, biomechanical, and performance-based descriptors at stiffness levels surrounding each subject’s preferred stiffness. Results Subjects preferred lower stiffness values at their self-selected treadmill walking speed, and elected to walk faster overground with ankle stiffness at or above their preferred stiffness. Preferred stiffness maximized the kinematic symmetry between prosthetic and unaffected joints, but was not significantly correlated with body mass or metabolic rate. Conclusion These results imply that some physiological factors are weighted more heavily when determining preferred stiffness, and that preference may be associated with clinically relevant improvements in gait
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the difference threshold of ankle foot prosthesis stiffness for persons with transtibial amputation
IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018Co-Authors: Max K Shepherd, Alejandro F Azocar, Matthew J Major, Elliott J. RouseAbstract:Most prosthetic feet behave like springs, and their stiffness affects many important facets of amputee gait. Despite the importance of prosthesis stiffness, the ability of amputees to sense stiffness changes-that is, distinguish between more or less stiff feet-is unknown. This perceptual resolution has implications for the methodology and overall significance of selecting the optimal foot stiffness during prescription. In this experiment, we used a Custom, Variable-stiffness ankle prosthesis to make small adjustments to stiffness in between steps, and below-knee amputees were asked to identify whether the ankle became more or less stiff. We determined that the average difference threshold of stiffness was 8%, meaning that subjects could correctly identify an 8% change in stiffness 75% of the time. This high sensitivity underscores the importance of optimizing prosthesis stiffness on an individual basis, and suggests a shift is needed in the characterization of commercial feet and the use of stiffness variation during the prescription process.
Alejandro F Azocar - One of the best experts on this subject based on the ideXlab platform.
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the difference threshold of ankle foot prosthesis stiffness for persons with transtibial amputation
IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018Co-Authors: Max K Shepherd, Alejandro F Azocar, Matthew J Major, Elliott J. RouseAbstract:Most prosthetic feet behave like springs, and their stiffness affects many important facets of amputee gait. Despite the importance of prosthesis stiffness, the ability of amputees to sense stiffness changes-that is, distinguish between more or less stiff feet-is unknown. This perceptual resolution has implications for the methodology and overall significance of selecting the optimal foot stiffness during prescription. In this experiment, we used a Custom, Variable-stiffness ankle prosthesis to make small adjustments to stiffness in between steps, and below-knee amputees were asked to identify whether the ankle became more or less stiff. We determined that the average difference threshold of stiffness was 8%, meaning that subjects could correctly identify an 8% change in stiffness 75% of the time. This high sensitivity underscores the importance of optimizing prosthesis stiffness on an individual basis, and suggests a shift is needed in the characterization of commercial feet and the use of stiffness variation during the prescription process.
Matthew J Major - One of the best experts on this subject based on the ideXlab platform.
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the difference threshold of ankle foot prosthesis stiffness for persons with transtibial amputation
IEEE International Conference on Biomedical Robotics and Biomechatronics, 2018Co-Authors: Max K Shepherd, Alejandro F Azocar, Matthew J Major, Elliott J. RouseAbstract:Most prosthetic feet behave like springs, and their stiffness affects many important facets of amputee gait. Despite the importance of prosthesis stiffness, the ability of amputees to sense stiffness changes-that is, distinguish between more or less stiff feet-is unknown. This perceptual resolution has implications for the methodology and overall significance of selecting the optimal foot stiffness during prescription. In this experiment, we used a Custom, Variable-stiffness ankle prosthesis to make small adjustments to stiffness in between steps, and below-knee amputees were asked to identify whether the ankle became more or less stiff. We determined that the average difference threshold of stiffness was 8%, meaning that subjects could correctly identify an 8% change in stiffness 75% of the time. This high sensitivity underscores the importance of optimizing prosthesis stiffness on an individual basis, and suggests a shift is needed in the characterization of commercial feet and the use of stiffness variation during the prescription process.