Master of Science, The Ohio State University, 2020, Vision Science

Purpose: To develop a meridional sphero-cylindrical subjective refraction method that does not require expensive equipment or extensive clinical training. To test the method empirically in normally-sighted subjects. Methods: Participants were 35 young, normally sighted subjects with natural pupils and accommodation. Subjects viewed Gaussian-attenuated square wave gratings at four orientations (0°, 45°, 90° and 135°) with a 2.3 cycle/degree fundamental spatial frequency. The maximum plus spherical dioptric power for best subjective clarity was determined for each grating orientation, yielding the refractive correction needed in the four cardinal meridians. The sphero-cylindrical correction is represented by the one cycle sinusoid that best fits those data. Within- and between-session test-retest differences in M, J0, and J45 were calculated, as were astigmatic and total dioptric power differences. Goodness-of-fit metrics were derived from the differences in measured values within each orientation, and from the differences between the measured values and the best-fitting sphero-cylindrical power. Visual acuity was measured with each resulting sphero-cylindrical correction. Results: In normally sighted subjects, median between-session test-retest differences for astigmatism are similar to published values for standard subjective refraction: ~0.13 D for both. Median differences for total dioptric power are larger than published values (0.26 D vs 0.20 D). The 95th percentile for astigmatic and total dioptric differences is larger by up to 40%, attributed to a greater number of outliers. LogMAR acuity is significantly correlated with the goodness-of-fit metrics. Conclusions: In normally sighted subjects, this method results in median test-retest difference distributions that are similar to those found with standard subjective refraction. Mean and 95th percentile values for refractive components are larger than those for standard subjective refraction. Those d (open full item for complete abstract)

Committee: Thomas Raasch OD PhD (Advisor); Bradley Dougherty OD PhD (Committee Member); Heather Anderson OD PhD (Committee Member) Subjects: Ophthalmology; Optics

Master of Science (MS), Wright State University, 2024, Earth and Environmental Sciences

The Teays River Valley is an ancient river valley system that existed before the Pleistocene Ice Age and spanned present-day Illinois, Indiana, Ohio, West Virginia, and Virginia. During the Pleistocene Ice Age, the Teays River Valley was buried by advancing continental glaciers and meltwater throughout most of its length. Due to the Teays' average width of roughly 2 miles and burial depth of approximately 200 meters (656 feet), the Ohio Geological Survey has been pursuing geophysical methods to map the location and depth of the Teays River Valley in Ohio. The present study is a refraction analysis using the first breaks from a seismic reflection dataset from west-central Ohio across the potential location of the buried Teays Valley. The seismic refraction results display a bedrock topography similar to the original seismic reflection profile, having an estimated bedrock depth along the profile roughly ranging from 24 m (79 ft) to 213 m (699 ft) in the buried valley. The refraction survey indicated average bedrock velocities of 3956 m/s (~13000 ft/s) and depths ranging from about 80 to 700 feet (24 to 213 meters), which is consistent with the reflection results and with a valley fill of unconsolidated sand and clay and limestone bedrock.

Committee: Christopher Barton Ph.D. (Committee Chair); Ernest C. Hauser Ph.D. (Committee Co-Chair); Doyle Watts Ph.D. (Committee Member) Subjects: Geological; Geology; Geophysics

Master of Science, The Ohio State University, 2024, Vision Science

Purpose: to investigate the utility and performance of a subjective and an objective meridional method of refraction on five additional keratoconic subjects and provide more critical evaluations of the conceptual approach, methods, and results from previous studies. Methods: Subjective and objective meridional refraction was performed on 25 subjects without cycloplegia. Four subjects had bilateral keratoconus and one had unilateral keratoconus. Targets for refraction were Gaussian-attenuated square wave gratings at four orientations (0⁰, 45⁰, 90⁰, 135⁰), with a bar width equal to 2x the subject's threshold letter size (i.e. for 20/20, 10 minarc/bar width, or 3 cycles/degree). The endpoint of the refraction was the spherical lens power required to achieve maximum grating contrast at each orientation. Lens power at each grating orientation was determined twice, and the spherocylindrical correction was derived from the dioptric power for those four orientations. Subjective refraction and visual acuity measurements were conducted using a manual minus-cylinder phoropter, while objective refraction relied on aberrometry measurement using a Wavefront Sciences COAS-CLAS 2D aberrometer. The objective refraction utilized Zernike coefficients obtained from aberrometry measurements to calculate spherocylindrical lens power that maximized contrast at eight orientations. Upon completion of both refractions, an adaptive staircase visual acuity measurement was conducted to assess the final refractive results, adjusting letter size based on subject responses to ensure an accurate threshold determination. The resulting data from each refraction in terms of final spherocylindrical power, visual acuity, and calculated retinal image were analyzed and compared. In addition to the meridional objective method, two other objective methods based on aberrometry (Visual Strehl Ratio and Minimized Root-Mean-Squared) were performed post-data collection on the data collected from all subjects (open full item for complete abstract)

Committee: Thomas Raasch (Advisor); Heather Anderson (Committee Member); Bradley Dougherty (Committee Member); Andrew Hartwick (Committee Member) Subjects: Health Sciences; Ophthalmology; Optics

Master of Science, The Ohio State University, 2022, Vision Science

Purpose: To evaluate subjective and objective refraction methods based on oriented grating targets. Methods: Subjective and objective meridional refraction was performed on 21 young normally-sighted subjects. Both the subjective and objective refraction methods were performed with and without cycloplegia. Targets for refraction were Gaussian-attenuated square wave gratings at four orientations (0⁰, 45⁰, 90⁰, 135⁰), with a bar width equal to 2x the subject's threshold letter size (i.e. for 20/20, 10 minarc/bar width, or 3 cycles/degree). The endpoint of the refraction was the spherical lens power to achieve maximum grating contrast. Lens power at each grating orientation was determined twice, and the sphero-cylindrical correction was derived from the dioptric power for those four orientations. The objective refractive correction was based on a measurement of ocular aberrations. In both the cyclopleged and non-cyclopleged conditions, aberration coefficients were transformed from those for the measured pupil diameter to a 3.5 mm pupil. As in the subjective method, the dioptric power to maximize grating contrast was found for each orientation, and the sphero-cylindrical correction was derived from those powers. Visual acuity was measured with the result of each refraction using an adaptive, maximum-likelihood method. Visual acuities with the result of the cycloplegic refraction were measured at a second visit, at least one day after the refraction visit. Results: Intra-session repeatability of M, J0, and J45 of dry subjective refraction was not significantly different from those found in a previous similar study (2-sample Kolmogorov-Smirnov test, p>.10). The standard deviations of M, J0, and J45 were 0.20D, 0.29D, and 0.22D, respectively, and is comparable to repeatability of standard methods of subjective refraction. Agreement between the different types of refraction was evaluated by examining differences in M, J0, J45, and in total dioptric power. Wet and (open full item for complete abstract)

Committee: Thomas Raasch (Advisor); Bradley Dougherty (Committee Member); Heather Anderson (Committee Member) Subjects: Ophthalmology; Optics

Master of Science (M.S.), University of Dayton, 2020, Electro-Optics

As the range of applications for electro-optic materials continues to grow, so does the need to identify and characterize new materials with improved electro-optic responses. A promising electro-optic material which has yet to be widely utilized is Lead Magnesium Niobate-Lead Titanate (PMN-PT) ceramic. In an effort to better characterize and understand the material, this work employed FTIR spectroscopy to calculate the refractive index of PMN-PT over a wide range of optical frequencies. Through analysis of interference fringes, the dispersion curve is calculated between 10,500 cm-1 and 1200 cm-1 (approximately 955 nm and 8.3 μm) containing nearly two thousand data points with an assumed accuracy of three decimal places. Additionally, capacitance bridge analysis is used to characterize the effect of temperature on the dielectric constant of PMN-PT. Special attention is given to the relationship of refractive index and dielectric constant so that a temperature study of the dielectric constant can be used to infer additional physical characteristics of PMN-PT.

Committee: Paul McManamon Ph.D. (Advisor) Subjects: Electrical Engineering; Electromagnetics; Experiments; Materials Science; Optics; Physics

Master of Science (MS), Wright State University, 2019, Earth and Environmental Sciences

This study focuses on northern Terre Haute, Indiana, where seven 2D seismic reflection time sections were collected by CountryMark and donated to Wright State University. Geologically, the area is on the eastern margin of the Illinois Basin. Two of these seismic lines display significant relief along a continuous, high-amplitude horizon approximately 180 milliseconds in two-way traveltime depth. This horizon was previously interpreted by CountryMark to be a Silurian reef core of the type common in this region of the Illinois Basin; however, other seismic lines within the data set display no relief. Furthermore, borehole logs within the area show no such relief at the equivalent depth of around 1700 feet. Therefore, the apparent structural high is an artifact within the two seismic lines, and can be called velocity pull-up. Various analyses were conducted to examine the causes of this velocity pull-up. The near-surface, within this region, contains many surfaces that may give rise to a velocity pull-up, including (1) the layer of weathered Pennsylvanian bedrock; (2) the Mississippian-Pennsylvanian Unconformity; and (3) an unconformity within Pennsylvanian section. It is possible that each of these surfaces could have enough relief to induce the observed velocity pull-up, and these possibilities were evaluated utilizing a combined analysis of Bouguer gravity, first-arrival traveltime tomography, passive seismic, and well log correlation. These multiple analyses show there is no Silurian reef core but a more complex velocity-inducing feature from a combination of the Mississippian-Pennsylvanian Unconformity and a shallower paleovalley fill.

Committee: Ernest C. Hauser Ph.D. (Committee Chair); Doyle R. Watts Ph.D. (Committee Member); David F. Dominic Ph.D. (Committee Member) Subjects: Geographic Information Science; Geology; Geophysical; Geophysics

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Mechanical Engineering

A detailed summary of the extensive studies on the feasibility and practicality of utilizing high-speed 3-dimensional digital image correlation (3D-DIC) for various random vibration measurement applications is presented. Demonstrated capabilities include finite element model validation and updating utilizing full-field 3D-DIC static displacements, modal survey natural frequencies, damping, and mode shape results from 3D-DIC are baselined against laser Doppler vibrometry (LDV), a comparison between foil strain gauge and 3D-DIC strain, and finally the unique application to a high-speed wind tunnel fluid-structure interaction study. Results indicate good agreement between 3D-DIC and more traditional vibration measurement techniques. Unfortunately, 3D-DIC vibration measurement is not without its limitations, which were also identified and explored in this study. The out-of-plane sensitivity required for vibration measurement for 3D-DIC is orders of magnitude less than LDV making higher frequency displacements difficult to sense. Furthermore, the digital cameras used to capture the DIC images have no filter to eliminate temporal aliasing of the digitized signal. Ultimately it is felt DIC was demonstrated as a valid alternative means to measure structural vibrations while providing full-field noncontacting results not possible with other methods. Furthermore, one unique first of its kind application in a high-speed wind tunnel achieved success where more traditional methods would fail.

Committee: Randall Allemang Ph.D. (Committee Chair); Allyn Phillips Ph.D. (Committee Member); S. Michael Spottswood Ph.D. (Committee Member); David Thompson Ph.D. (Committee Member); Yongfeng Xu Ph.D. (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2018, Electrical and Computer Engineering

This dissertation investigates the propagation of all electromagnetic fields inside anisotropic metamaterials using the Berreman 4 x 4 matrix method. Specifically, the Berreman matrix is used to derive the forward and backward propagating electric fields inside anisotropic metamaterials for all polarizations. Results from the Berreman method are compared with those obtained from the transfer matrix method and finite element methods. Examples include transmissivity and reflectivity as a function of wavelength and angle of incidence for multi-layer metallo-dielectric stacks and dielectric-phase change material stacks, modeled using effective medium theory for Berreman matrix calculations. It is shown that the Berreman matrix method used along with effective medium theory provides a fast and reliable estimate of the optical characteristics of the composite material. The Berreman technique also readily leads to the transfer function matrix for beam propagation in anisotropic materials. The eigenvalues of the Berreman matrix, which determine the transfer function, depend on the anisotropy. Beam propagation in anisotropic materials is analyzed both theoretically and numerically. It is shown that for transverse magnetic polarization, self-lensing of beams occur in a hyperbolic metamaterial. Finally, the transmission coefficient, which is a function of the spatial frequency, is used to determine the spatial shifts of beams propagating through anisotropic metamaterials. Again, for transverse magnetic polarization, negative refraction is observed. The results should prove useful for the analysis of arbitrary beam profiles through composite metamaterials.

Committee: Partha Banerjee (Committee Chair); Joseph Haus (Committee Member); Monish Chatterjee (Committee Member); Guru Subramanyam (Committee Member); Todd Smith (Committee Member) Subjects: Electrical Engineering; Electromagnetics; Optics; Physics

Doctor of Philosophy, The Ohio State University, 2018, EDU Teaching and Learning

This dissertation attempts to address three areas of significance to the current academic zeitgeist: 1) the disciplinary re-characterization of English composition in consideration of its ability to aid the transfer of writing practices, 2) the increasing theorization of writing in academic settings as sets of social practices, 3) the repeated calls for serious research to be conducted in college and university writing centers. Using ethnographic methods and tools, I conducted a semester-long study in which I observed participants in a first-year composition (FYC) class and the required tutorials in the school's writing center. This dissertation focuses on the work done for one assignment, the Primary Source Analysis (PSA). Grounded in the academic literacies model of Lea and Street (1998, 2006), my research looks at how the literacy practices of the PSA are theorized, taught, and taken up in three contexts. First, the institutional and curricular context: How do the school's course curriculum and the school's writing center conceive the teaching and learning of writing academically? Second, the classroom context: How does the classroom instructor reflect and refract institutional literacy practices? And third, the tutorial context: How do the case study students and writing tutors reflect and refract both institutional literacy practices and those literacy practices constituted in Dr. Joyce's classroom as the students move between the classroom and the writing center? In response to these questions, I identified a list of practices associated with the PSA and analyzed these practices through the frame of reflection and refraction (e.g., Bloome & Brown, 2012). I use classroom documents, administrator interviews, and the class text to characterize the practices within the institutional and curricular context. Then I trace how the classroom instructor, peer writing consultants (PWCs), and students reflect and refract the FYC practices prescribed and imparted by those (open full item for complete abstract)

Committee: George Newell PhD (Advisor); Caroline Clark PhD (Committee Member); Beverly Moss PhD (Committee Member) Subjects: Education; Literacy

Doctor of Philosophy, The Ohio State University, 1977, Graduate School

Committee: Not Provided (Other) Subjects: Education

Master of Science (MS), Wright State University, 2015, Earth and Environmental Sciences

An experiment was conducted to constrain the HVSR (Horizontal to Vertical Spectral Ratio) or H/V spectral ratio method at a glaciated site in northeast Ohio. Multiple methods were used to determine the shear wave velocity (Vs) and depth (h) to bedrock in relation to the fundamental resonant frequency (fo) determined from 3-component seismic data, as defined by the relationship f0=Vs/4h. The shear wave velocity structure was determined at three sites using MASW (Multi-channel Analysis of Surface Waves) and shear wave refraction methods, and the fundamental resonant frequency was passively observed using 3-component Guralp broadband seismometers. The Vs and bedrock depth results from both refraction and MASW produced comparable calculated theoretical f0 to that observed by the 3-component broadband seismometers. However, the bedrock depth and glacial drift Vs results were consistently lower for refraction than for MASW. Part of the calculations used with the generalized reciprocal method (GRM) method could yield bedrock depths that are underestimated proportionally with the Vs. Notably, the MASW results appear to be improved by combining overtones of multiple source offsets. The average Vs from the MASW and refraction surveys of this study were each used to calculate bedrock depth using the f0 observed for a suite of 73 seismometers previously deployed across the surrounding area as part of another study. Maps of these calculated bedrock depths correlate with the major dipping trends indicated by the water and gas wells in the area. At the site where the closest comparison could be made, the MASW determined Vs yielded a depth to bedrock that was significantly closer to the measured bedrock depth than the refraction determined Vs. This study suggests that an average shear wave velocity for glacial drift determined from a few MASW surveys in a region is sufficient to determine a viable average Vs to convert an array of 3-component f0 observations to pr (open full item for complete abstract)

Committee: Ernest Hauser Ph.D. (Advisor); Doyle Watts Ph.D. (Committee Member); David Dominic Ph.D. (Committee Member) Subjects: Geophysical; Geophysics

Master of Science (MS), Wright State University, 2015, Earth and Environmental Sciences

In July 2013, an industry-scale seismic reflection survey was conducted at a site in northern Jay County, Indiana, by geophysics students and faculty of Wright State University. As a part of that effort, a separate near-surface seismic dataset was collected to examine the Vp, Vs, and Poisson's Ratio of the glacial drift and upper bedrock. This near-surface study successfully used a common dataset that was separately analyzed for both Vp (seismic refraction) and Vs (MASW) to calculate the Poisson's Ratio of the glacial drift and underlying bedrock. The driller's log for a water well near the east end of this near-surface survey indicates glacial drift (unconsolidated clay and sand) overlies limestone bedrock at a depth of 110 feet. Water wells in the broader area show bedrock depth varying from 110 to 122 feet, but locally as much as 140 feet. The near-surface seismic data were acquired using a Bison EWG (Elastic Wave Generator) assisted weight drop source that shot every station through a stationary spread of 48 channels using a pair of 24-channel Geode seismographs. Each channel recorded a a single vertical 4.5 Hz geophone at a station spacing of 10 feet. Four weight drop records at each source point were summed to enhance the S/N ratio. The same data volume was processed both for Vs using SurfSeis3 MASW (Multichannel Analysis of Surface Wave) software and for Vp using IXRefrax3 refraction software. The MASW results suggest that the depth to bedrock at the survey location ranges from 115-120 feet (~35 m) with Vs of 1,200-2,000 ft/sec (366-610 m/s) for glacial drift and 2,400-2,700 ft/sec (730-823 m/s) for bedrock. The P-wave refraction results suggest the depth to bedrock ranges from 118-122 feet (36-37 m) with average Vp of ~5,000 ft/sec (1,524 m/s) for glacial drift and ~17,000 ft/sec (5180 m/s) for limestone bedrock. The Poisson's Ratio for the glacial drift calculated using the Vp and Vs at common locations in this study is 0.470-0.473, which i (open full item for complete abstract)

Committee: Ernest Hauser Ph.D. (Advisor); Doyle Watts Ph.D. (Committee Member); David Dominic Ph.D. (Committee Member) Subjects: Energy; Geophysical; Geophysics

Master of Science (M.S.), University of Dayton, 2015, Electro-Optics

Nonlinear absorption is a phenomenon in which the transmission of light through a sample is dependent upon the intensity of the incident light, caused by the process of two photon and carrier absorption. At low intensities the material will be transparent, but at high intensities the material will be opaque. Nonlinear refraction is a phenomenon by which the index of refraction of a material is dependent upon the incident intensity of the light. This leads to an effect known as self focusing, by which intense light creates a refractive gradient that focuses or defocuses the beam according to the transverse spatial distribution of the laser focus. These two properties are important in the development of optical switches. This work will measure these nonlinear properties for the material Cadmium Magnesium Telluride. Special attention is given to the relation of these properties to the bandgap of the compound, which is dependent upon the concentration of magnesium dopant. The data was collected using the Irradiance Scan technique in both the nanosecond and picosecond regimes, and the data was analysed using a four objective iterative approach involving both first order analytical approximations and a full numerical nonlinear propagation analysis.

Committee: Shekhar Guha Ph.D. (Committee Chair); Partha Banerjee Ph.D. (Committee Member); Jay Matthews Ph.D. (Committee Member) Subjects: Materials Science; Optics; Physics

Master of Arts (MA), Ohio University, 2014, English (Arts and Sciences)

These poems are the culmination of an experiment toward understanding how certain celestial phenomena influence our inner and outer lives in an abundance of ways that simply go undetected by the senses. In an effort to both understand the inner life's relation to the outer, the poems undertake the project (through a dream-like tone, crafted to convey the speaker's journey of rediscovering senses) of understanding the relationship of humans and the world, perspective and self. Split between the concepts of refraction and reflection, The Boy with the Aluminum Hat is a metaphor, a voice-piece to vocalize both the paranoia of never understanding our lives and the desire to know the truth of existence. Both sections collide with the anxiety of living in the world on a daily basis. Simultaneously, the poems illustrate the body's relation to this world that it is rooted to and from which it is occasionally uprooted.

Committee: Halliday Mark (Advisor) Subjects: American Literature; Earth; Electromagnetics; Personality

Master of Science, University of Akron, 2014, Geology-Geophysics

Ground penetrating radar (GPR), electrical resistivity and seismic refraction surveys were used to image possible buried sinkholes and identify potential areas of subsidence in the shallow paleokarst surface of the Columbus Limestone at Ohio Caverns in Champaign County, Ohio. A buried sinkhole, incipient sinkholes and a possible buried cave passage spatially correlated with orthoimagery and surface evidence of subsidence. Correlations were established by using GIS software overlaying a structure-contour map of the paleokarst, as determined by GPR data, over orthoimagery of the area. Wenner and dipole-dipole electrical resistivity surveys suggest regions of lower resistivity surrounded by higher resistivity are associated with suspected subsidence. Refraction seismic data, collected along the same transect as the resistivity surveys, also correlated with an area of depression in the region of a suspected sinkhole. The seismic velocities from the refraction survey indicated lower depths for the clay soil and Ohio Shale contact and also the boundary between the Ohio Shale and the Columbus Limestone. Remote sensing using electrical resistivity, GPR and seismic refraction techniques successfully imaged the stratigraphy of the area and suggest other areas of incipient sinkhole formation.

Committee: David Steer Dr. (Advisor); John Peck Dr. (Committee Member); Ira Sasowsky Dr. (Committee Member) Subjects: Environmental Geology; Geographic Information Science; Geological; Geology; Geophysical; Geophysics

Master of Science (MS), Wright State University, 2012, Physics

An optical material parameter predictive model that accounts for sample to air interfaces was developed. The model predicts how a terahertz time-domain spectroscopy time domain pulse will be affected as it passes through a given thickness of a material. The model assumes a homogenous, linear, isotropic dielectric or semiconductor. The inputs to the model are the real and imaginary refractive indices across the desired frequency band. Different dielectric material's optical parameters were taken from the literature and the predicted time domain pulses were shown. It was also shown that the refractive index and absorption coefficient for samples that were optically thick and low-loss could be determined from measurements analytically. It was also shown that for non-dispersive media with a flat absorption coefficient, the predictive model could be used to determine an average value for both the index of refraction and the absorption coefficient across the frequency band, (0.1-4 terahertz).

Committee: Jason Deibel PhD (Advisor); Douglas Petkie PhD (Committee Member); Gregory Kozlowski PhD (Committee Member) Subjects: Physics

Master of Science, University of Toledo, 2007, College of Arts and Sciences

Although gravity and magnetic field data have been used to infer variations in the crustal structure of Ohio, seismic evidence regarding the depth to the Mohorovicic discontinuity is sparse. First arrivals from 13 regional earthquakes recorded by the Ohio Seismic Network between 2001 and 2006 were examined to investigate variations in crustal composition and thickness in Ohio and attempt to calculate the depth to the mantle. The average crustal structure consists of two layers: Paleozoic sedimentary rock over granitic crust (phase Pg) overlying the mantle (phase Pn). The average apparent P-wave velocities for the Paleozoic sedimentary rock and granitic crust are 4.8 km/s and 5.5 km/s respectively. Reduced travel time curves of first arrivals show nodirect evidence of a higher (~ 6.8 km/s) velocity lower crust (crustal phase Pb). Paleozoic sedimentary rock thickness, determined from well data, ranges from 700 m in western Ohio to over 4 km in southeastern Ohio. Calculated thicknesses of the Paleozoic sedimentary rock (-5.8 ± 8.8 km in western Ohio, 26.9 ± 25.8 km in southeastern Ohio) and granitic crust (20.1 ± 10.1 km in western Ohio, 57.6 ± 29.6 km in southeastern Ohio) beneath each station, determined from regional earthquake residuals (1.8 ±1.8 seconds early in western Ohio, 5.0 ± 5.4 seconds late in southeastern Ohio), have a mean value higher than thicknesses derived from well data and gravity and magnetic field interpretations. However, these results involve large standard deviations that span crustal models previously proposed. Comparing these thicknesses determined from regional earthquakes with thicknesses determined from teleseismic earthquakes and Earthscope Automated Receiver Survey (EARS) seismic data show small variations beneath most stations. Those stations with large variations between regionally, teleseismically, and EARS determined thicknesses also have a small number of regional earthquake observations.

Committee: Donald Stierman (Advisor) Subjects: Geology; Geophysics

Master of Science, The Ohio State University, 2012, Vision Science

Optical signals of the peripheral retina control eye growth and associated myopia more than previously believed. Traditional thought held that the fovea must play the largest role in progression of refractive error because of its integral role in vision. However, recent research shows that the peripheral retina may be involved. In Rhesus monkeys, peripheral form deprivation and optically induced hyperopia lead to increased axial elongation and myopia. Furthermore, emmetropization occurs when the peripheral cue is removed, even after ablation of the central retina. Human myopes have relative hyperopic blur in the periphery, whereas emmetropes and hyperopes exhibit emmetropia or myopia in the retinal periphery. In fact, relative peripheral hyperopia precedes myopia onset by two years in children. This peripheral hyperopic blur may be a signal for myopic eye growth. Tracking the 3-dimensional shape of the eye through peripheral measurements could provide clues about how peripheral blur increases axial elongation. Understanding these optical signals and pathways could be valuable in ultimately determining how to manage or prevent myopia. Research has focused on methods to stymie eye growth by inducing peripheral myopic defocus. It is therefore important to determine whether any change in peripheral eye length is greater than that which can be expected by measurement error alone. This study aims to determine the inter-occasion repeatability of peripheral axial length measurements using the IOLMaster in order to learn more about the growth of peripheral eye. To assess the repeatability of the IOLMaster in measuring peripheral eye length, we performed five measurements of both non-cycloplegic and cycloplegic (two drops of 1% tropicamide) axial length in primary gaze and at gazes 20 degrees nasal, temporal, superior, and inferior. The same examiner repeated the measurements one week (± 2 days) later to assess how similar the measurements were from one week to the next, assu (open full item for complete abstract)

Committee: Jeffrey Walline OD PhD (Advisor); Donald Mutti OD PhD (Committee Member); Gilbert Pierce OD PhD (Committee Member) Subjects: Ophthalmology; Optics

Doctor of Philosophy, The Ohio State University, 2009, Mathematics

Based on Lagrangian formulations of the Lorentz equations of motion, we investigate the relativistic orbit of a classical charged particle in response to a generic electromagnetic field in the four dimensional Minkowski space. Within the context of classical mechanics, the results are relativistically and mathematically exact. With the application to laser-particle interaction in mind, our primary focus is on the particle dynamics in a generic plane wave field.Taking advantage of the fact that the particle motion in the direction transverse to the wave propagation direction is cyclic, we use the classical Routh's procedure to reduce the number of degrees of freedom of the motion and to manifest the observation that the longitudinal motion of the particle controls every aspect of the particle dynamics under the influence of a generic plane wave field. In fact, we show that the particle longitudinal motion is a generalized natural mechanical system in the sense that it has a Lagrangian consists of the difference of a metric based kinetic energy and a potential function. A corollary of this is the culmination of this work, that is, the geodesic variational principle. The geodesic variational principle implies that longitudinally, the particle moves along a timelike geodesic in a curved two dimensional Lorentzian spacetime whose metric is determined by the plane wave field. In other words, the effect of the field on the particle dynamics gets replaced by the effect of the geometry and its curvature on the geodesics of a two-dimensional manifold. This gives rise to a geometrization of the laser-particle interaction. We also use the geodesic variational principle to establish a Lorentzian law of refraction in which the particle, in response to the plane wave field, gets refracted by the field in the same way that light rays get refracted by a medium permeating Euclidean space. The plane wave field acts as a refractive medium with a characteristic Lorentzian refractive ind (open full item for complete abstract)

Committee: Ulrich Gerlach (Advisor); Ovidiu Costin (Committee Member); David Terman (Committee Member) Subjects: Mathematics

Doctor of Philosophy, The Ohio State University, 2009, Vision Science

A two-year, double-masked, randomized clinical trial of myopic children 6 to 11 years old is being conducted using progressive addition lenses (PALs) to evaluate two theories of juvenile-onset myopia progression. Eligible children had a high accommodative lag and either: (1) low myopia (less myopic than –2.25 D spherical equivalent) or (2) high myopia (more myopic that –2.25 D spherical equivalent) with esophoria at near. The accommodative lag theory hypothesizes that hyperopic retinal blur drives myopia progression. The mechanical tension theory hypothesizes that ciliary-choroidal tension created by the ocular components restricts equatorial expansion and causes axial elongation in people with factors that produce a large globe. To test between these theories, children were randomly assigned to wear either PALs with a +2.00-D add or single vision lenses (SVLs) for one year to achieve a reduction in myopia progression in the PAL group relative to the SVL group. All children then wear SVLs for the second year to evaluate the permanence of the treatment effect; a maintained treatment effect supports the lag theory, while a rebound supports mechanical tension. The primary outcome is central cycloplegic autorefraction. Complete ocular biometric data are being collected at six-month intervals. Over 17 months, 192 children were screened, and 85 (44%) were eligible and enrolled. The mean age (± SD) was 9.3 ± 1.4 years. The mean accommodative lag was 1.71 ± 0.37 D, and 54 children (64%) were esophoric at near. The mean cycloplegic spherical equivalent refractive error and axial length were –1.95 ± 0.78 D and 24.17 ± 0.80 mm, respectively. Baseline characteristics of the children enrolled are described. Because the clinical trial is ongoing, all findings are confidential. Aberrometry-based relative peripheral refraction measurements were validated against measurements made with an autorefractor. A method of analyzing peripheral aberration data collected from a dilated pupil (open full item for complete abstract)

Committee: Karla Zadnik OD, PhD (Advisor); Donald O. Mutti OD, PhD (Advisor); Nicklaus Fogt OD, PhD (Committee Member) Subjects: Optics