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C Okamoto - One of the best experts on this subject based on the ideXlab platform.
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influence of induced decentered orthokeratology lens on ocular higher order wavefront aberrations and contrast Sensitivity Function
Journal of Cataract and Refractive Surgery, 2009Co-Authors: Takahiro Hiraoka, C Okamoto, Fumiki Okamoto, Toshifumi Mihashi, Yoko HiroharaAbstract:Purpose To quantitatively evaluate the effect of overnight orthokeratology lenses intentionally left decentered after 3 months of wear and assess the influence on clinical outcomes such as ocular higher-order wavefront aberrations and contrast Sensitivity Function. Setting Department of Ophthalmology, Tsukuba University Hospital, Ibaraki, Japan. Methods This prospective study assessed refraction, visual acuity, corneal topography, wavefront aberration, and contrast Sensitivity Function before and 3 months after overnight orthokeratology treatment. Decentration of the treatment zone from the center of the entrance pupil was determined using computerized videokeratography (TMS-4) and data-analysis software (MatLab). The relationship between decentration and the clinical parameters was analyzed. Results The mean age of the 23 patients (46 eyes) was 24.2 years±3.3 (SD) and the mean spherical equivalent refraction before treatment, −2.38±0.98 diopters. The mean magnitude of decentration (0.85±0.51 mm) was statistically significantly correlated with the amount of myopic correction (P Conclusion Decentered treatment of orthokeratology resulted in decreased contrast Sensitivity after treatment, showing that centration of the procedure is crucial to good outcomes.
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contrast Sensitivity Function and ocular higher order aberrations following overnight orthokeratology
Investigative Ophthalmology & Visual Science, 2007Co-Authors: Takahiro Hiraoka, C Okamoto, Yuko Ishii, Tetsuhiko KakitaAbstract:PURPOSE. To evaluate relationships among contrast Sensitivity Function, ocular higher-order aberration, and myopic correction in eyes undergoing overnight orthokeratology for myopia. METHODS. A prospective study was conducted in 46 eyes of 23 patients undergoing orthokeratology. Inclusion criteria were spherical equivalent refraction between - 1.00 and - 4.00 diopters (D), refractive astigmatism up to 1.00 D, and best-corrected visual acuity of 20/20 or better. Ocular higher-order aberrations and contrast Sensitivity Function were determined before and 3 months after initiation of the procedure. We measured three indices of contrast Sensitivity Function: contrast Sensitivity, low-contrast visual acuity, and letter contrast Sensitivity with the CSV-1000 charts (Vector Vision Co., Greenville, OH). Area under the log contrast Sensitivity Function (AULCSF) was calculated from the contrast Sensitivity data. RESULTS. Orthokeratology significantly improved logMAR uncorrected visual acuity (P < 0.0001; paired t-test) but significantly increased ocular higher-order aberrations (P < 0.0001) and decreased contrast Sensitivity Function, including AULCSF (P < 0.0001), low-contrast visual acuity (P = 0.0025), and letter contrast Sensitivity (P < 0.0001; Wilcoxon signed-rank test). The induced changes in AULCSF, low-contrast visual acuity, and letter contrast Sensitivity by orthokeratology showed significant correlation with changes in third-order (Pearson r = -0.430, P = 0.0026; r = 0.423, P = 0.0031; and Spearman r s = -0.351, P = 0.0186, respectively), fourth-order (r = -0.418, P = 0.0035; r = 0.425, P = 0.0029; and r s = - 0.566, P = 0.0001, respectively), and total higher-order (r = -0.460, P = 0.0011; r = 0.471, P = 0.0008; and r s = -0.434, P = 0.0036, respectively) aberrations. The induced changes in contrast Sensitivity Function and higher-order aberrations significantly correlated with the amount of myopic correction (P < 0.01). CONCLUSIONS. Orthokeratology significantly increases ocular higher-order aberrations and compromises contrast Sensitivity Function, depending on the amount of myopic correction.
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contrast Sensitivity Function and ocular higher order wavefront aberrations in normal human eyes
Ophthalmology, 2006Co-Authors: Tetsuro Oshika, Tadatoshi Tokunaga, Tomokazu Samejima, C Okamoto, Kazunori MiyataAbstract:Purpose To investigate the relation between contrast Sensitivity Function and ocular higher-order wavefront aberrations in normal human eyes. Study Design Prospective observational case series. Participants Three hundred seven eyes of 161 normal subjects, ranging in age from 15 to 60 years (30.9±8.0 [mean ± standard deviation]). Methods Ocular higher-order aberrations were measured for a 4-mm pupil using the Hartmann–Shack wavefront analyzer. The root-mean-square of the third- and fourth-order Zernike coefficients was used to represent comalike and spherical-like aberrations, respectively. We measured contrast Sensitivity, low-contrast visual acuity (VA), and letter contrast Sensitivity. From the contrast Sensitivity data, the area under the log contrast Sensitivity Function (AULCSF) was calculated. Pupil diameter in a photopic condition was recorded using a digital camera. Results Multiple linear regression analysis revealed that comalike aberration ( P = 0.002) was significantly associated with AULCSF, but spherical-like aberration ( P = 0.200), age ( P = 0.185), and photopic pupil diameter ( P =0.252) were not. Comalike aberration showed a significant correlation with low-contrast VA ( P P = 0.293), age ( P = 0.266), and pupil diameter ( P = 0.756) did not. Comalike aberration was found to be significantly associated with letter contrast Sensitivity ( P P =0.082), age ( P = 0.370), and pupil diameter ( P = 0.160) were not. Conclusions In normal human eyes, comalike aberration of the eye significantly influences contrast Sensitivity Function.
Umberto Viaro - One of the best experts on this subject based on the ideXlab platform.
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a bounded complementary Sensitivity Function ensures topology independent stability of homogeneous dynamical networks
IEEE Transactions on Automatic Control, 2018Co-Authors: Franco Blanchini, Daniele Casagrande, Giulia Giordano, Umberto ViaroAbstract:This paper investigates the topology-independent stability of homogeneous dynamical networks, composed of interconnected equal systems. Precisely, dynamical systems with identical nominal transfer Function $F(s)$ are associated with the nodes of a directed graph, whose arcs account for their dynamic interactions, described by a common nominal transfer Function $G(s)$ . It is shown that topology-independent stability is guaranteed for all possible interconnections with interaction degree (defined as the maximum number of arcs leaving a node) equal at most to $N$ if the $\infty$ -norm of the complementary Sensitivity Function $NF(s)G(s)[1+NF(s)G(s)]^{-1}$ is less than 1. This bound is nonconservative in that there exist graphs with interaction degree $N$ that are unstable for an $\infty$ -norm greater than 1. When nodes and arcs transferences are affected by uncertainties with norm bound $K > 0$ , topology-independent stability is robustly ensured if the $\infty$ -norm is less than $1/(1+2NK)$ . For symmetric systems, stability is guaranteed for all topologies with interaction degree at most $N$ if the Nyquist plot of $NF(s)G(s)$ does not intersect the real axis to the left of $-1/2$ . The proposed results are applied to fluid networks and platoon formation.
Ioan Dore Landau - One of the best experts on this subject based on the ideXlab platform.
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brief combined pole placement Sensitivity Function shaping method using convex optimization criteria
Automatica, 1999Co-Authors: J Langer, Ioan Dore LandauAbstract:This paper deals with the design of robust digital controllers by the combined pole placement/Sensitivity Function shaping method. The problem of assigning a desired region for the closed-loop poles and simultaneously respecting certain bounds on the Sensitivity Functions is formulated and solved as a convex optimization problem. Specifications like dominant closed-loop poles or integration controller action may be introduced just as well as other fixed parts for the controller. The method is illustrated by the controller design for a very flexible 360^o arm.
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robust digital control using pole placement with Sensitivity Function shaping method
International Journal of Robust and Nonlinear Control, 1998Co-Authors: Ioan Dore Landau, Alireza KarimiAbstract:SUMMARY It is shown in this paper that based on identified discrete-time models a robust digital linear controller can be designed using the pole placement method combined with Sensitivity Function shaping in the frequency domain. Two di⁄erent design techniques are presented. The first one is based on the shaping of the Sensitivity Functions using the fixed parts in the controller and the auxiliary poles of the closed loop while keeping the dominant poles in the desired places. The main idea of the second one is to determine a weighting filter for the output Sensitivity Function in an H = optimization approach which assures partial pole placement and desired performances. In this technique the weighting filter is interpreted as the inverse of the desired output Sensitivity Function and is computed using a constrained optimization program. The application of this technique on a flexible transmission system is presented. ( 1998 John Wiley & Sons, Ltd. The controller design methodology considered in this paper is based on pole placement combined with the shaping of the Sensitivity Function. The computation of the controller in the pole placement technique requires the specification of the desired closed-loop poles (the nominal stability problem) and of some fixed parts of the controller for the rejection of disturbances at various frequencies (the nominal performance problem). However, this is not enough to guarantee the robustness of the design with respect to the plant model uncertainties (the robust stability and robust performance problem). A robust controller design requires also the shaping of the Sensitivity Functions. The Sensitivity Functions, particularly the output Sensitivity Function, are key indicators for the nominal and robust performance as well as for the robust stability of the closed-loop system. The inverse of the maximum value of the output Sensitivity Function, i.e., the inverse of its H = norm, gives the minimum distance between the Nyquist plot of the open-loop system and the critical point [!1, j0]. This quantity, called the modulus margin, is a much more significant robustness indicator than the phase and gain margins. On the other hand, conditions for assuring a certain delay margin which is also a very important robustness indicator, particularly in the high frequency region, can also be expressed in terms of the shape of the output Sensitivity Function. It seems therefore reasonable to combine the pole placement with the shaping of the output
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robust digital control of flexible transmissions using the combined pole placement Sensitivity Function shaping method
European Journal of Control, 1995Co-Authors: Ioan Dore Landau, Alireza Karimi, Alina Voda, D ReyAbstract:The control of very flexible transmissions in the presence of load variations is a challenging control problem. In this paper it is shown that based on identified discrete time models a robust digital linear controller can be designed using the combined pole placement method with Sensitivity Function shaping in the frequency domain. This controller provides satisfactory performance for a large range of load variations.
Takahiro Hiraoka - One of the best experts on this subject based on the ideXlab platform.
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Improvement in Contrast Sensitivity Function after Lacrimal Passage Intubation in Eyes with Epiphora.
Journal of clinical medicine, 2020Co-Authors: Sujin Hoshi, Kuniharu Tasaki, Takahiro HiraokaAbstract:This prospective case series aimed to investigate the contrast Sensitivity Function before and after lacrimal passage intubation (LPI) in eyes with epiphora due to lacrimal passage obstruction. We included 58 eyes of 51 patients who underwent LPI for lacrimal passage obstruction. The best-corrected visual acuity (BCVA), contrast Sensitivity Function, and lower tear meniscus were compared before LPI and one month after lacrimal duct stent removal. The area under the log contrast Sensitivity Function (AULCSF) was calculated for the analyses. Lower tear meniscus was assessed using anterior segment optical coherence tomography. The BCVA was comparable (p = 0.61) before and after LPI, while AULCSF increased significantly after treatment (before LPI: 1.29 ± 0.17, after LPI: 1.37 ± 0.14, p < 0.0001). Treatment resulted in a significant increase in contrast Sensitivity at all spatial frequencies, 3–18 cycles/degree (p < 0.01 for 3, p < 0.01 for 6, p < 0.0005 for 12, p < 0.05 for 18 cycles/degree). The lower tear meniscus parameters improved significantly after treatment (p < 0.005); however, no correlation between the changes in the tear meniscus and those of the AULCSF was found. The contrast Sensitivity significantly improved after LPI in eyes with epiphora due to lacrimal passage obstruction.
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influence of induced decentered orthokeratology lens on ocular higher order wavefront aberrations and contrast Sensitivity Function
Journal of Cataract and Refractive Surgery, 2009Co-Authors: Takahiro Hiraoka, C Okamoto, Fumiki Okamoto, Toshifumi Mihashi, Yoko HiroharaAbstract:Purpose To quantitatively evaluate the effect of overnight orthokeratology lenses intentionally left decentered after 3 months of wear and assess the influence on clinical outcomes such as ocular higher-order wavefront aberrations and contrast Sensitivity Function. Setting Department of Ophthalmology, Tsukuba University Hospital, Ibaraki, Japan. Methods This prospective study assessed refraction, visual acuity, corneal topography, wavefront aberration, and contrast Sensitivity Function before and 3 months after overnight orthokeratology treatment. Decentration of the treatment zone from the center of the entrance pupil was determined using computerized videokeratography (TMS-4) and data-analysis software (MatLab). The relationship between decentration and the clinical parameters was analyzed. Results The mean age of the 23 patients (46 eyes) was 24.2 years±3.3 (SD) and the mean spherical equivalent refraction before treatment, −2.38±0.98 diopters. The mean magnitude of decentration (0.85±0.51 mm) was statistically significantly correlated with the amount of myopic correction (P Conclusion Decentered treatment of orthokeratology resulted in decreased contrast Sensitivity after treatment, showing that centration of the procedure is crucial to good outcomes.
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contrast Sensitivity Function and ocular higher order aberrations following overnight orthokeratology
Investigative Ophthalmology & Visual Science, 2007Co-Authors: Takahiro Hiraoka, C Okamoto, Yuko Ishii, Tetsuhiko KakitaAbstract:PURPOSE. To evaluate relationships among contrast Sensitivity Function, ocular higher-order aberration, and myopic correction in eyes undergoing overnight orthokeratology for myopia. METHODS. A prospective study was conducted in 46 eyes of 23 patients undergoing orthokeratology. Inclusion criteria were spherical equivalent refraction between - 1.00 and - 4.00 diopters (D), refractive astigmatism up to 1.00 D, and best-corrected visual acuity of 20/20 or better. Ocular higher-order aberrations and contrast Sensitivity Function were determined before and 3 months after initiation of the procedure. We measured three indices of contrast Sensitivity Function: contrast Sensitivity, low-contrast visual acuity, and letter contrast Sensitivity with the CSV-1000 charts (Vector Vision Co., Greenville, OH). Area under the log contrast Sensitivity Function (AULCSF) was calculated from the contrast Sensitivity data. RESULTS. Orthokeratology significantly improved logMAR uncorrected visual acuity (P < 0.0001; paired t-test) but significantly increased ocular higher-order aberrations (P < 0.0001) and decreased contrast Sensitivity Function, including AULCSF (P < 0.0001), low-contrast visual acuity (P = 0.0025), and letter contrast Sensitivity (P < 0.0001; Wilcoxon signed-rank test). The induced changes in AULCSF, low-contrast visual acuity, and letter contrast Sensitivity by orthokeratology showed significant correlation with changes in third-order (Pearson r = -0.430, P = 0.0026; r = 0.423, P = 0.0031; and Spearman r s = -0.351, P = 0.0186, respectively), fourth-order (r = -0.418, P = 0.0035; r = 0.425, P = 0.0029; and r s = - 0.566, P = 0.0001, respectively), and total higher-order (r = -0.460, P = 0.0011; r = 0.471, P = 0.0008; and r s = -0.434, P = 0.0036, respectively) aberrations. The induced changes in contrast Sensitivity Function and higher-order aberrations significantly correlated with the amount of myopic correction (P < 0.01). CONCLUSIONS. Orthokeratology significantly increases ocular higher-order aberrations and compromises contrast Sensitivity Function, depending on the amount of myopic correction.
Yoko Hirohara - One of the best experts on this subject based on the ideXlab platform.
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influence of induced decentered orthokeratology lens on ocular higher order wavefront aberrations and contrast Sensitivity Function
Journal of Cataract and Refractive Surgery, 2009Co-Authors: Takahiro Hiraoka, C Okamoto, Fumiki Okamoto, Toshifumi Mihashi, Yoko HiroharaAbstract:Purpose To quantitatively evaluate the effect of overnight orthokeratology lenses intentionally left decentered after 3 months of wear and assess the influence on clinical outcomes such as ocular higher-order wavefront aberrations and contrast Sensitivity Function. Setting Department of Ophthalmology, Tsukuba University Hospital, Ibaraki, Japan. Methods This prospective study assessed refraction, visual acuity, corneal topography, wavefront aberration, and contrast Sensitivity Function before and 3 months after overnight orthokeratology treatment. Decentration of the treatment zone from the center of the entrance pupil was determined using computerized videokeratography (TMS-4) and data-analysis software (MatLab). The relationship between decentration and the clinical parameters was analyzed. Results The mean age of the 23 patients (46 eyes) was 24.2 years±3.3 (SD) and the mean spherical equivalent refraction before treatment, −2.38±0.98 diopters. The mean magnitude of decentration (0.85±0.51 mm) was statistically significantly correlated with the amount of myopic correction (P Conclusion Decentered treatment of orthokeratology resulted in decreased contrast Sensitivity after treatment, showing that centration of the procedure is crucial to good outcomes.
