Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Astigmatism"”.
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Posterior Corneal Astigmatism
… different astigmatic magnitudes and axes. Total astigmatism of the cornea is determined by the combination of both anterior corneal astigmatism and posterior corneal astigmatism. In order to treat astigmatism of the eye during cataract surgery precisely, total corneal astigmatism needs to be …
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Analysis and Correction of Corneal Astigmatism in Modern Pseudophakia
… spectacle dependency by correcting corneal astigmatism at the time of surgery. However, these IOLs are reliant on the accurate prediction of post-operative corneal astigmatism through reliable ocular biometry and the accurate calculation of surgically induced astigmatism. In the thesis the …
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The Role of Corneal Astigmatism When Fitting Orthokeratology Contact Lenses
… one-third of children aged 5-17 years old have astigmatism. Children with increasing astigmatism can also have an accompanying increase in myopia via axial elongation. All of the randomized clinical trials to date have excluded patients with more than 1.50 D of astigmatism and there are limited …
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Visual Performance in Pseudophakia. The Effect of Meridional Blur in Pseudoaccommodation.
… of meridional blur, using refractive induced astigmatism, on visual performance at far and close distances. Visual performance was evaluated using letter discrimination tasks at distance and near (visual acuity, VA) and a reading task at near on subjects with pharmacologically blocked (young) …
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The development of a predictive autofocus algorithm using a general image formation model
… of a general imaging model for use in autofocus, astigmatism correction, and resolution analysis. The model is based on the modulation transfer function of the imaging system in the presence of aberrations, in particular defocus. The extension of the model to include astigmatism is also included. …
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Consolidating Approaches to Maximise Outcomes and Minimise Complications of Contemporary Cataract Surgery
… with toric intraocular lenses to correct corneal astigmatism (N=200 eyes). This study revealed excellent visual outcomes and low residual refractive astigmatism. To assess relative dexterity in eye surgery the Eyesi® Surgical virtual reality simulator was used to evaluate the dominant hand (DH) …
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Clinical Translation of Dynamic OCE for Corneal Biomechanical Assessment
… corneal toricity and biomechancial anisotropy in astigmatism and 2) mapping biomechanical heterogeneity in keratoconus. Results: Air-pulse generated broadband, high-frequency (>5 kHz) corneal waves were detected with 0.19 nm sensitivity. The air-pulse OCE system achieved ~0.29 kPa mechanical …
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An algorithm for rapid measurement of aberrations in pairs of out-of-focus images
… accuracies of 0.08 um for coma, 0.08 um for astigmatism, 0.9 um for tilt, and 0.3 um for defocus. It was also quite fast, with an average of 34 iterations until convergence.
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The correction of borderline refractive and heterophoric anomalies
… of � +0.75, reading additions of � +0.75DS and astigmatism of � -0.75DC. For asymptomatic patients, practitioners’ likelihood of prescribing exceeded 50% for: reading additions of �+1.50DS and astigmatic corrections of �-1.50DC. In the absence of symptoms, optometrists would not regularly …
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Algorithms for the application of Hartmann-Shack wavefront sensors in ophthalmology
… a sphere of -11.25 dpt to 3.25 dpt and an astigmatism of up to 4 dpt. In the field of image processing, procedures were developed, which allow to recognize strongly aberrated wavefronts. Numerous algorithms are presented, which are suitable to use the extensive raw data to get some …
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Influence of ocular monochromatic aberrations in the development and/or progression of myopia
… the eyes with Type III skiagram (asymmetry in astigmatism in nasal and temporal quadrants) showed the most myopic change in refraction. It may be possible this asymmetry in astigmatism (characteristic feature of Type III skiagram) observed at temporal retina could play a role in myopic change …
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Coherence-Gated Wave-Front Sensing in Strongly Scattering Samples
… two wave-front aberrations, defocus and astigmatism, for a mirror as a sample and a strongly scattering sample. The results are compared to theoretical models. The main advantage of CGWS is the discrimination against light backscattered from outside the focal region. A further advantage …
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Adaptation to Interocular Differences in Blur
… to simulate different levels and axes of astigmatism. Adaptation to both types of blur produced strong aftereffects that showed strong transfer across the eyes. Greater transfer was found for the isotropic blur than for the oriented blur, both in a monocular adaptation task and in a …
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Ocular biometric change in orthokeratology. An investigation into the effects of orthokeratology on ocular biometry and refractive error in an adult population.
… -4.00DS with low levels of with the rule corneal astigmatism. The use of an aspheric back design contact lens did not produce a significant benefit over that of a pentacurve.
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Clinician measurement of spectacle prescription changes and patient tolerance to them
… VA to full threshold. The change in ocular astigmatism from with- to against-the-rule with age was more than three times more likely to pass through oblique axes than a spherical prescription. 36% of eyes were found to have an oblique cylinder prescribed at least once and of these, 78% were …
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Refractive Outcome in Eyes of Preterm Infants
… the others. The prevalence and the degree of astigmatism were similar among three groups. There were no significant differences in the axial length and anterior chamber depth between group 1 and 3. The degree of myopia was related to laser or cryotherapy treated eyes, birth weight, …
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Web-based system for outcome analysis and modification in laser vision correction
… refractive disorders, such as compound myopic astigmatism, have shown less predictable refractive outcomes, and in some cases the severe over- or under-correction can even worsen the preoperative situation and damage the eye. In its first stage, this research aimed to develop a software system …
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Visual Function in New Zealand Children: from Preschool to Primary School
… their peers. Refractive error, most commonly astigmatism (65-80% of cases), was present in up to one third of children. Up to 84% of New Zealand children with ametropia did not have appropriate correction. While the current vision screening programme was effective for detecting children with …
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Gravitational Lensing and Telescope Aberrations
… on images of flexed galaxies. Telescope astigmatism, coma, and trefoil distort stellar images in much the same way that gravitational shear and flexion distort galaxy images. In this chapter, I derive simple models for lensed galaxies and for aberrated PSFs, and convolve the two models to …
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Heme Oxygenase-2 as a novel target to treat inflammation and chronic neuropathic pain associated with corneal injury and surgery
… the cornea correlated with myopia, hyperopia and astigmatism. More than 12 million patients have undergone refractive surgery since it was approved (see http://www. laser-eye-surgery statistics.com/). Laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are the most …
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