Dissertationen zum Thema „Correction de refraction“
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Dia, Amadou Sall. „Quantitative ultrasound imaging of human cortical bone“. Electronic Thesis or Diss., Sorbonne université, 2024. https://theses.hal.science/tel-04650855.
Der volle Inhalt der QuelleOsteoporosis is a disease characterized by a decrease in bone mass and an increase in porosity, weakening the bones and potentially leading to fragility fractures. Globally, one-third of women over the age of 50 and one-fifth of men aged over 50 will experience osteoporosis-related fractures, contributing to over 8.9 million fractures annually worldwide. Early detection and treatment can prevent these fractures. Several techniques have been developed to assess bone quality, with ultrasound emerging as a cost-effective, portable, and safe option. Ultrasound imaging of the cortex of long bones allows for the evaluation of bone quality by estimating cortical thickness and ultrasonic wave-speed, which are biomarkers of mechanical strength and fracture risk. However, challenges arise with increased cortical porosity in osteoporotic bone, making it difficult to detect the inner surface (endosteum) and limiting image quality. The aim of this study is to design an image reconstruction technique to enhance ultrasound images of cortical bone. This involves understanding the factors influencing image quality. Synthetic and experimental ultrasound datasets were generated to achieve this. The results demonstrate successful estimation of cortical thickness and ultrasonic wave-speed using ultrasound imaging for homogeneous cortical bone. In vivo estimation of wave-speed at the tibial cortex of healthy individuals achieved a precision of less than 3%. However, for degraded bones, increased cortical porosity and vascular pore size create speckle that obscures the visibility of the endosteal interface. A novel refraction-corrected specular beamforming algorithm was proposed to improve the visibility of the endosteal interface. Application of this algorithm to both ex vivo and in vivo datasets revealed enhanced visibility compared to traditional Delay-and-Sum (DAS) beamforming. This study provides a better understanding of factors affecting bone ultrasound image contrast and proposes considering scatterers as specular reflectors to enhance endosteal interface visibility. By evaluating the specularity of the endosteal interface, it becomes possible to potentially assess the roughness of the endosteum. This opens a way for designing new bone mechanical quality quantifiers. Bone ultrasound imaging shows promise in identifying and monitoring individuals with low cortical bone mechanical quality at risk of osteoporotic fracture
Feurer, Denis. „Géométrie 3D des lits de rivière par stéréophotogrammétrie à travers l'eau“. Phd thesis, AgroParisTech, 2008. http://tel.archives-ouvertes.fr/tel-00818380.
Der volle Inhalt der QuelleO'Leary, Claire Iris. „The correction of borderline refractive and heterophoric anomalies“. Thesis, City, University of London, 2009. http://openaccess.city.ac.uk/17552/.
Der volle Inhalt der QuelleNoma, Regina Kazumi. „Problemática da correção óptica em escolares: acesso, comparecimento, necessidade e uso de óculos“. Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/5/5149/tde-07122011-131618/.
Der volle Inhalt der QuelleINTRODUCTION: The lack of optical correction was recently recognized as an important cause of low vision and it seems to be an easy problem to be solved with the use of spectacles. However, it is a complex problem from its diagnosis to treatment, which includes medical assistance searching and finding, and spectacles acquisition and use. PURPOSES: To determine the frequency of optical correction need; to determine the impact of the recall of those absent in the ophthalmologic service coverage and its causes; to check the previous ophthalmologic coverage; to check the use of the prescribed optical correction and causes to neglect the use of spectacles. METHOD: An analytical cross-sectional study was conducted. Students between 7 and 10 years old of public education from Guarulhos were screened and referred to ophthalmologic exam in the Eye to Eye Campaign 2006 and 2007. RESULTS: 40.197 students were screened and 11.741 (29,2%) were referred with suspicion of visual problems. The absenteeism in the first call was 42.5% and in the recall 62.2%. The Campaign reached 73.6% of the referred students. The recall expanded the project coverage in 16.1%. The lack of guidelines (parents did not receive notification or referral guide) was the most frequent reason (35.6%) provided by parents for the non attendance, followed by work (20.6%) and disease (12.4%). The need of glasses was not related to the attendance. For 60.2% of the students, it was the first opportunity for ophthalmological exam, whereby 27.3% searched but did not have access to a medical visit. Among the 1.379 students who had already performed an exam, 48.3% used the Public Health System and 1.029 received prescription of glasses in the previous exam. From those, 899 (87.4%) made their glasses and only 590 (57.3%) were wearing glasses on the day of the exam. From the donated spectacles in the Campaign, 84.7% of the students were using the donated optical correction after one year. The estimate of optical correction need within the studied population was 6.9%. CONCLUSIONS: The uncorrected refractive error was the main cause of low visual acuity among students. The Campaign was the first opportunity of ocular exam for most of them. A significant number of parents did not take their children for ophthalmological exams, even when facilities (access, free transportation, meal, two different opportunities of free exam over the weekend and spectacle donation) were offered. For 87.1% of the absenteeism cases, the difficulties could have been overcome via improved structuring of the first call. A recall is not recommended when financial resources are low
Armstrong, Deborah. „The Role of vision and refractive correction changes in dizziness“. Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/16956.
Der volle Inhalt der QuelleCollege of Optometrists sponsored the research with a Postgraduate Research Scholarship
Koivula, Annemari. „Long-term results of phakic refractive lenses for correction of myopia and hyperopia /“. Stockholm, 2007. http://diss.kib.ki.se/2007/978-91-7357-424-2/.
Der volle Inhalt der QuelleTang, Maolong. „Corneal mean curvature mapping application in laser refractive surgery /“. The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1094593446.
Der volle Inhalt der QuelleSalmon, Anne. „Higher-order aberrations in amblyopia : an analysis of pre- and post-wavefront-guided laser refractive correction“. Thesis, Aston University, 2015. http://publications.aston.ac.uk/25159/.
Der volle Inhalt der QuelleEarl, Thomas Anthony. „Characterisation of turbulence in an open channel flow and in a fountain with tomographic PIV“. Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12814.
Der volle Inhalt der QuelleRenner, Kimberly. „Academic Performance of Oyler School Students after Receiving Spectacle Correction“. The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1491593613366446.
Der volle Inhalt der QuelleLewis, Peter. „Improving Peripheral Vision Through Optical Correction and Stimulus Motion“. Doctoral thesis, Linnéuniversitetet, Institutionen för medicin och optometri (MEO), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-52286.
Der volle Inhalt der QuelleLloyd, Joshua S. „Commercialization of Software for the Prediction of Structural and Optical Consequences Resulting from Corneal Corrective Treatments“. Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1447778132.
Der volle Inhalt der QuelleMccafferty, Sean Joseph. „Analysis and Application of Opto-Mechanics to the Etiology of Sub-Optimal Outcomes in Laser Corrective Eye Surgery and Design Methodology of Deformable Surface Accommodating Intraocular Lenses“. Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/556806.
Der volle Inhalt der QuellePesochinsky, Nina. „Effect of refractive vision correction of myopia and hyperopia through laser surgery (LASIK & PRK) on symptoms of depression, stress perception and self-esteem in adults (22-55)“. Thesis, Capella University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10288076.
Der volle Inhalt der QuelleThe purpose of this study was to assess the effects of refractive vision correction through laser surgery (LASIK & PRK) of adults of working age (22-55). This study examined and compared the symptoms of depression, stress perception, and self-esteem prior to surgery and one month after surgery, when sufficient healing has occurred. Research has shown that vision impairment has been reported to be one of the 10 most significant causes of disability in the United States, and, even though clinicians are encouraged to assess emotional response to vision loss, the psychological factors that that play a role in adjustment to vision loss have not been sufficiently studied.
Delmas, Anthony. „Contribution à l'étude de l'effet mirage : application aux mesures dimensionnelle et thermique par caméras visible proche infrarouge“. Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/8958/1/delmas.pdf.
Der volle Inhalt der QuelleNien, Wei-Jen, und 粘為任. „Use total focusing method and refraction correction to improve phase array acoustic image“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/61893796839114389060.
Der volle Inhalt der Quelle國立中正大學
地震研究所暨應用地球物理研究所
97
Compare to single element traditional ultrasonic probe, The phased array source which has several elements is widely used in medical images and nondestructive testing (NDT), Because of its excellent controllable, so we can transmit any direction wavefront by time shift. The synthetic aperture focusing technique (SAFT)is use in traditional ultrasonic probe, and total focusing method (TFM)is use in phased array probe. Both of synthetic aperture focusing technique and total focusing method are a way to improve acoustic image. In nondestructive testing, we usually need to face the problem of refraction. So in this paper we will combine TFM and refraction correction in order to improve acoustic image. Finally, using the phased array probe with transmitting time shift, TFM and refraction correction can built the high resolution 3D image volume.
SU, KAI, und 蘇愷. „Optical design of contact lens with peripheral refractive correction“. Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3bs9s3.
Der volle Inhalt der Quelle國立中正大學
光機電整合工程研究所
106
Myopia is considered an urgent public health problem due to the impact of the global population and the burden of visual disability. An estimated 1.5 billion people were affected in 2010. Myopia is the most common cause of permanent visual impairment and is expected to increase by nearly 5 billion by 2050. Based on the peripheral refractive theory, this study designed a contact lens that can change the peripheral refraction of the retina,and established a measurement system that can measure the refractive state of the eyeball. The ASAP optical simulation software was used to analyze the retina under different refractive conditions. The image, together with the optimization, calculates the refractive power vector as the basis for correcting the effect. The purpose of this study is to cause relative myopia or peripheral hyperopia to control the growth of the axial growth of the eye to control the development of myopia. According to the results, the fourth-order spherical aberration peripheral refractive lens model constructed in this study is used, which has a good corrective effect on myopia control. Keywords: peripheral refraction, lens design, myopia control
Lee, Chiungwu, und 李瓊武. „Study of the atomospheric refractive correction for a medium-range EDM“. Thesis, 1994. http://ndltd.ncl.edu.tw/handle/18040501992782243359.
Der volle Inhalt der Quelle國立中央大學
地球物理學系
82
Results obtained in this study indicated that the internal precision of ME5000 distance measuring system, is about ±(0.1+0.1‧D)mm, where D is distance in km. An uncertainty of external precision in the absolute length system of light speed, as indicated from a comparison of the EOM results with Vaisala interference results - i.e., the most accurate method of determining the baseline length. Furthmore, its stability and accuracy has become the foundation for examining the atmospheric refraction correction for a medium - range EDM in the study. Due to long distance, the temperature, pressure and relative humidity are normally taken at the ends of the line during EDM. The averages of temperature, pressure and relative humidity from endpoints measurments are used to represent the true values along the wavepath length. As a consequence, the errors may cause a great restriction for the accuracy of EDM. This study, as based on the theory of atmospheric temperature model of Angus-Leppan and Brunner (1980), primarilly aims at analyzing the successive EDM data in Hsin Chu Medium-Range baseline as well as proposing a more practical and suitable temperature model for local area. Consequently, the error of group refractive index can be reduced and the accuracy improved. Furthermore, multi-layer atmospheric potential temperature model based on Webb (1964) was included to evaluate the additional correction when the elevation difference of EDM line is over the Obukhov length. This could be of help to raise the accuracy of EDM in Geodesy and the detection of crust deformation in Geophysics.
丁政揚. „Optical Design of RGP Contact Lens for Peripheral Refractive Error Correction“. Thesis, 2016. http://ndltd.ncl.edu.tw/handle/58350535213330421050.
Der volle Inhalt der Quelle逢甲大學
電機工程學系
104
This paper proposes a multi-layer structure of RGP contact lenses design for peripheral refractive error correction of myopia. The structure is a combination of free-form、even-aspherical and biconic surface. This article describes contact lenses design procedure to correct visual aberration, such as defocus、coma and astigmatism, from the 〖30〗^° temporal side to the 〖30〗^° nasal side. Compared to a conventional contact lens, our design can simultaneously correct the defocus on central field and peripheral field on the retina. It expands the clear visual scope and avoids the further deterioration of myopia. The greatest feature of this design is that we combine three layers together. The first surface is biconic for correcting astigmatism, the second is even-aspherical for correcting high-order aberrations, and the third surface is of free-form to correct off-axis defocus at retina, the last surface is spherical with a radius of curvature matching the front surface of cornea. This design provides more flexibility and optimizable parameters to correct high order aberrations, while correcting the defocus on peripheral field. Thus achieve a better visual image quality, finally field at 0°、±10°、±20°、±30° which cutoff frequency is sequentially 110lp/mm, 35lp/mm, 20lp/mm and 15lp/mm of MTF values have reached 0.3.
YU, YA-CHUN, und 于雅君. „Study of the Influence of both Optimum Refractive Correction and Refractive Spherical Equivalent of Distance Vision on Intraocular Pressure“. Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t3knuy.
Der volle Inhalt der Quelle逢甲大學
視光科技碩士在職學位學程
106
The purpose of this study was to develop a new technique of vision correction and promote the visual comfort. The single-pole brainwave extractor and tonometer were applicated to measure the results of the vision correction using the full-correction (MPMVA) lens or the spherical equivalent lens. In the study, the volunteers with astigmatic refractive error wearing MPMVA lens or the spherical equivalent lens received the exam of the single-pole brainwave extractor. When the brainwave exam revealed the focus, the vision was clear. The tonometry were performed after wearing the lens for 15 minutes. About the result, the elevated intraocular pressure (3.33mmHg, right eye and 2.00mmHg, left eye) after wearing the spherical equivalent lens comparing to MPMVA lens were found in the group of low astigmatic refractive error. In the group of high astigmatic refractive error, the elevated intraocular pressure of the right eye (1.33mmHg) was found. The change of the intraocular pressure revealed the difference of MPMVA lens and the spherical equivalent lens. To promote the visual comfort, we suggest using MPMVA lens, especially in the group of low astigmatic refractive error.
Boyle, Matthew J. „Comparison of laser vision correction outcomes with two excimer laser nomograms“. Thesis, 2020. https://hdl.handle.net/2144/41153.
Der volle Inhalt der Quelle2022-06-07T00:00:00Z
Supuk, Elvira, Alison J. Alderson, Christopher J. Davey, Clare Green, Norman Litvin, Andy J. Scally und David B. Elliott. „Dizziness, but not falls rate, improves after routine cataract surgery: the role of refractive and spectacle changes“. 2015. http://hdl.handle.net/10454/8366.
Der volle Inhalt der QuellePurpose To determine whether dizziness and falls rates change due to routine cataract surgery and to determine the influence of spectacle type and refractive factors. Methods Self-reported dizziness and falls were determined in 287 patients (mean age of 76.5 ± 6.3 years, 55% females) before and after routine cataract surgery for the first (81, 28%), second (109, 38%) and both eyes (97, 34%). Dizziness was determined using the short-form of the Dizziness Handicap Inventory. Six-month falls rates were determined using self-reported retrospective data. Results The number of patients with dizziness reduced significantly after cataract surgery (52% vs 38%; χ2 = 19.14, p < 0.001), but the reduction in the number of patients who fell in the 6-months post surgery was not significant (23% vs 20%; χ2 = 0.87, p = 0.35). Dizziness improved after first eye surgery (49% vs 33%, p = 0.01) and surgery on both eyes (58% vs 35%, p < 0.001), but not after second eye surgery (52% vs 45%, p = 0.68). Multivariate logistic regression analyses found significant links between post-operative falls and change in spectacle type (increased risk if switched into multifocal spectacles). Post-operative dizziness was associated with changes in best eye visual acuity and changes in oblique astigmatic correction. Conclusions Dizziness is significantly reduced by first (or both) eye cataract surgery and this is linked with improvements in best eye visual acuity, although changes in oblique astigmatic correction increased dizziness. The lack of improvement in falls rate may be associated with switching into multifocal spectacle wear after surgery.
This work was supported by The Dunhill Medical Trust(grant number SA14/0711).
Cox, Michael J., und Holger H. Dietze. „Correcting ocular spherical aberration with soft contact lenses“. 2004. http://hdl.handle.net/10454/3471.
Der volle Inhalt der QuelleFollowing aberroscopy, aspheric front surface soft contact lenses (SCLs) were custom-made to correct spherical refractive error and ocular spherical aberration (SA) of 18 myopic and five hypermetropic subjects (age, 20.5 . 5 yr). On-eye residual aberrations, logMAR visual acuity, and contrast sensitivity were compared with the best-correcting spectacle lens, an equally powered standard SCL, and an SCL designed to be aberration free in air. Custom-made and spherical SCLs reduced SA ( p . 0.001; p . 0.05) but did not change total root-meansquare (rms) wave-front aberration (WFA). Aberration-free SCLs increased SA ( p . 0.05), coma ( p . 0.05), and total rms WFA. Visual acuity remained unchanged with any of the SCL types compared with the spectacle lens correction. Contrast sensitivity at 6 cycles/degree improved with the custom-made SCLs ( p . 0.05). Increased coma with aspheric lens designs and uncorrected astigmatism limit the small possible visual benefit from correcting ocular SA with SCLs.
Chiou, Yi-Shiuan, und 邱怡萱. „The study of correcting the spherical aberration of a refractive lens with a diffractive lens“. Thesis, 1996. http://ndltd.ncl.edu.tw/handle/78264325031079182052.
Der volle Inhalt der Quelle國立交通大學
電子物理學系
84
The diffractive lens is characteristic of thinness and lightness, and cost effective. The diffractive lens has the same imaging principle as refractive lens. In the traditional optical design, since a single lens has too much aberration, we need two or more refractive lensesto correct the aberration, but now we can easily use a single diffractivelens to improve the performance of a single lens. The aberration of a diffractive lens can be evaluated with the aberration formula of a refrctivelens in which the refrctive index is taken to be infinite. In this thesis, at first we will describe the aberrationfomula of the diffractive lens and simulate the imaging of the optical system.Then we describe how to make a diffractive lens by using the IC technology.At last we measure and evaluate the imaging quality of the optical system.
Nitz, Michael Allen. „A retrospective analysis of visual outcomes in laser vision correction of hyperopic patients using the VISX STAR S4 IR® and the WaveLight® EX500 excimer laser platforms“. Thesis, 2017. https://hdl.handle.net/2144/23725.
Der volle Inhalt der Quelle2018-01-11T00:00:00Z