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1
Sivaraman, Viswanathan. "Nearwork-induced transient myopia in myopic and non-myopic Indian subjects." Thesis, Anglia Ruskin University, 2016. https://arro.anglia.ac.uk/id/eprint/702946/6/Sivaraman_2016.pdf.
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This research project investigated the characteristics of near-work induced transient myopia (NITM) in asymptomatic myopes and non-myopes among Indian subjects and its variation with target size and contrast. NITM was defined as the post-task distance refraction minus the pre-task distance refraction. In the first two studies NITM magnitude was greater and the decay was faster among myopes for 5 minutes and 60 minutes of near task respectively. There was no influence of target size and contrast on NITM parameters. In the third study Zernike wave-front co-efficient values were measured using COAS (complete ophthalmic analysis system) before and immediately after 5 minutes of near task to investigate the effect of near task on higher order aberrations among myopes and non myopes. Aberration values did not show significant differences for pre and post 5 minutes of near task. In the fourth study axial length, corneal thickness, AC depth and lens thickness were measured with the Bio-graph (Allegro, wave light) instrument before and immediately after 5 minutes of near task to investigate the influence of near task on biometry readings among myopes and non-myopes. Axial length, corneal thickness, AC depth, lens thickness did not show significant differences following 5 minutes of near task. In the fifth study 31 myopes were recruited to assess the NITM parameters in pre and post Lasik refractive surgery. NITM magnitude was higher in pre-Lasik myopic subjects compared to post-Lasik myopic subjects. Most of the accommodative parameters especially the lag of accommodation and facility of accommodation improved following the surgery.
2
Sivaraman, Viswanathan. "Nearwork-induced transient myopia in myopic and non-myopic Indian subjects." Thesis, Anglia Ruskin University, 2016. http://arro.anglia.ac.uk/702946/.
Full textAbstract:
This research project investigated the characteristics of near-work induced transient myopia (NITM) in asymptomatic myopes and non-myopes among Indian subjects and its variation with target size and contrast. NITM was defined as the post-task distance refraction minus the pre-task distance refraction. In the first two studies NITM magnitude was greater and the decay was faster among myopes for 5 minutes and 60 minutes of near task respectively. There was no influence of target size and contrast on NITM parameters. In the third study Zernike wave-front co-efficient values were measured using COAS (complete ophthalmic analysis system) before and immediately after 5 minutes of near task to investigate the effect of near task on higher order aberrations among myopes and non myopes. Aberration values did not show significant differences for pre and post 5 minutes of near task. In the fourth study axial length, corneal thickness, AC depth and lens thickness were measured with the Bio-graph (Allegro, wave light) instrument before and immediately after 5 minutes of near task to investigate the influence of near task on biometry readings among myopes and non-myopes. Axial length, corneal thickness, AC depth, lens thickness did not show significant differences following 5 minutes of near task. In the fifth study 31 myopes were recruited to assess the NITM parameters in pre and post Lasik refractive surgery. NITM magnitude was higher in pre-Lasik myopic subjects compared to post-Lasik myopic subjects. Most of the accommodative parameters especially the lag of accommodation and facility of accommodation improved following the surgery.
3
Ting, Wai Ki. "Instrument myopia and myopia progression in Hong Kong microscopists." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15958/1/Wai_Ki_Ting_Thesis.pdf.
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People who work in occupations that involve intensive near work are thought to have a higher chance of developing myopia than other people. For example, microscopists in the United Kingdom have a higher prevalence of myopia than that of the general community. The prevalence of myopia in Hong Kong is extremely high (71 %) and Hong Kong Chinese people are particularly susceptible to myopia development and progression due to environmental factors. It is possible that this environmental susceptibility may lead to Hong Kong Chinese microscopists developing even
greater levels of myopia. We found that the prevalence of myopia in Hong Kong microscopists (n=47, mean age=31 years) was higher than that of United Kingdom microscopists (87 % c.f. 71 %) and similar aged people within the general Hong
Kong population (87 % c.f. 71 %; −4.45 D c.f. -3.00 D). However, while in most microscopists (83 % of 36 microscopists followed for a two-year period) the amount of myopia and vitreous chamber depth increased over a two year monitoring period (−0.11 D, 0.06 mm), the increase was not clinically significant. We hypothesised that the slower myopia progression rate in Hong Kong microscopists may be the result of their older average age (Hong Kong microscopists: 31.7 years c.f. United Kingdom
microscopists: 29.7 years).
When a person looks into a microscope, excessive accommodation occurs even though the microscope is designed to render the magnified image at optical infinity (zero accommodation and vergence demand). This over accommodation is called instrument myopia. It is possible that this over accommodation is linked to the myopia development and progression that occurs in users of these instruments. We found that instrument myopia remained consistent with different viewing conditions and microscope settings (inexperienced microscopists, n=20, mean age: 24.1 years, mean spherical refractive error: −2.83 D). The magnitude of instrument myopia was
not correlated with either the age or refractive error of the microscope user, while it was lower in those users with greater experience (inexperienced microscopists: 1.03
D c.f. experienced microscopists: 0.43 D). As the Hong Kong microscopists (n=10, mean age: 31.2 years, mean spherical refractive error: −3.39 D) who partook in this study were experienced (6.3 years spent working in this field), this may have contributed to the lower myopia progression that was observed.
Studies to determine the main contribution to the phenomena of instrument myopia were also conducted. Instrument myopia was not correlated with convergence when looking into microscope (r= −0.224, p=0.342), near phoria (r=0.351, p=0.129), AC/A ratio (r= −0.135, p=0.571), the convergence induced by the excessive accommodative response (r= −0.028, p=0.906), lag of accommodation (r=0.065, p=0.785) and tonic accommodation (r=0.142, p=0.551). We suggest that the main contribution to instrument myopia during microscopy is proximal accommodation
due to the awareness of the closeness, caused by the height of the microscope (i.e. the distance between the viewer and the table where the microscope is placed), during microscopy. For example, we found that the magnitude of instrument myopia increased significantly (from 0.64 D to 1.16 D) when the height of the microscope decreased from 50 cm to 35 cm.
In conclusion we have added, through direct observation, to the understanding of the
characteristics of instrument myopia. Guidelines for new microscopists aimed at minimising the amount of instrument myopia that is experienced have been developed. This information might help to reduce the amount of myopia progression
in commencing microscopists.
4
Ting, Wai Ki. "Instrument myopia and myopia progression in Hong Kong microscopists." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15958/.
Full textAbstract:
People who work in occupations that involve intensive near work are thought to have a higher chance of developing myopia than other people. For example, microscopists in the United Kingdom have a higher prevalence of myopia than that of the general community. The prevalence of myopia in Hong Kong is extremely high (71 %) and Hong Kong Chinese people are particularly susceptible to myopia development and progression due to environmental factors. It is possible that this environmental susceptibility may lead to Hong Kong Chinese microscopists developing even greater levels of myopia. We found that the prevalence of myopia in Hong Kong microscopists (n=47, mean age=31 years) was higher than that of United Kingdom microscopists (87 % c.f. 71 %) and similar aged people within the general Hong Kong population (87 % c.f. 71 %; −4.45 D c.f. -3.00 D). However, while in most microscopists (83 % of 36 microscopists followed for a two-year period) the amount of myopia and vitreous chamber depth increased over a two year monitoring period (−0.11 D, 0.06 mm), the increase was not clinically significant. We hypothesised that the slower myopia progression rate in Hong Kong microscopists may be the result of their older average age (Hong Kong microscopists: 31.7 years c.f. United Kingdom microscopists: 29.7 years). When a person looks into a microscope, excessive accommodation occurs even though the microscope is designed to render the magnified image at optical infinity (zero accommodation and vergence demand). This over accommodation is called instrument myopia. It is possible that this over accommodation is linked to the myopia development and progression that occurs in users of these instruments. We found that instrument myopia remained consistent with different viewing conditions and microscope settings (inexperienced microscopists, n=20, mean age: 24.1 years, mean spherical refractive error: −2.83 D). The magnitude of instrument myopia was not correlated with either the age or refractive error of the microscope user, while it was lower in those users with greater experience (inexperienced microscopists: 1.03 D c.f. experienced microscopists: 0.43 D). As the Hong Kong microscopists (n=10, mean age: 31.2 years, mean spherical refractive error: −3.39 D) who partook in this study were experienced (6.3 years spent working in this field), this may have contributed to the lower myopia progression that was observed. Studies to determine the main contribution to the phenomena of instrument myopia were also conducted. Instrument myopia was not correlated with convergence when looking into microscope (r= −0.224, p=0.342), near phoria (r=0.351, p=0.129), AC/A ratio (r= −0.135, p=0.571), the convergence induced by the excessive accommodative response (r= −0.028, p=0.906), lag of accommodation (r=0.065, p=0.785) and tonic accommodation (r=0.142, p=0.551). We suggest that the main contribution to instrument myopia during microscopy is proximal accommodation due to the awareness of the closeness, caused by the height of the microscope (i.e. the distance between the viewer and the table where the microscope is placed), during microscopy. For example, we found that the magnitude of instrument myopia increased significantly (from 0.64 D to 1.16 D) when the height of the microscope decreased from 50 cm to 35 cm. In conclusion we have added, through direct observation, to the understanding of the characteristics of instrument myopia. Guidelines for new microscopists aimed at minimising the amount of instrument myopia that is experienced have been developed. This information might help to reduce the amount of myopia progression in commencing microscopists.
5
Laffont, Jean-Jacques, and Jean Tirole. "Managerial switching and myopia." MIT Energy Lab, 1987. http://hdl.handle.net/1721.1/27203.
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Li, Zeyu, and 黎泽宇. "Literature review on children myopia." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45173151.
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Holmes, Craig. "Myopia, retirement planning and commitment." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:980da095-60ab-47b5-a4e2-3962085d56ca.
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Decisions made by individuals planning for retirement may be myopic. One way of capturing this myopia is with quasi-hyperbolic discounting. It is well known that such preferences may explain why individuals fail to provide an adequate retirement income for themselves. In this thesis, the quasi-hyperbolic discounting model is applied to a number of other decisions and outcomes related to planning for retirement. There are three main focuses. Firstly, the thesis considers a model where individuals are quasi-hyperbolic discounters over both retirement and saving, and extends the results of Diamond and Köszegi (2003). It argues that mechanisms designed to overcome myopic saving decisions may lead to unplanned early retirement. This may depend on the form of income in retirement -- regular income options such as annuities offer commitment over overconsuming early in retirement, which makes early retirement less desirable to myopic retirees. Secondly, it tests these predictions using a new laboratory experiment. Over a two-month period, participants were asked to attend weekly sessions, and could leave the experiment (or "retire") in any week of their choosing. Part of their payment for attending these sessions was put aside and paid only after they had left. The results indicated that more impulsive individuals left the experiment earlier, both overall and relative to plans made in the first week of the experiment. Finally, this thesis presents a model of rising wages as a forced saving mechanism. Assuming individuals face some borrowing constraints, deferred wages implicitly place some earnings aside until much closer to retirement, when quasi-hyperbolic discounters save a greater fraction of their income, increasing total retirement wealth. It also shows that demand for rising wages should disappear for people with access to more direct saving commitment mechanisms, although when these schemes offer less commitment (due to early withdrawal or early retirement options), a combination of both mechanisms is preferred.
8
Huang, Yu. "Gene-environment interactions in myopia." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/114604/.
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Myopia, as a common ocular disorder, is caused by both genetic and environmental factors. Conventional genome-wide association studies (GWAS) in humans have limited power to detect myopia genes partly due to the complex interplay between genes and environment. Here, I performed a GWAS in a sample of chicks with form deprivation (FD) myopia, aiming to reduce environmental complexity and increase the statistical power to detect genetic variants that confer susceptibility to this environmentally-induced myopia phenotype. The degree of FD myopia was quantified by measuring the treatment-induced changes in axial length (∆AXL) and mean spherical equivalent (∆MSE). Body weight, sex, and batch were evaluated as potential confounding factors. To reduce costs, chicks in the phenotype extremes (lowest or highest ∆AXL, within each batch) were selected for genotyping. To identify genetic variants conferring susceptibility to myopia, GWA analyses for ∆AXL and ∆MSE were applied to the genotype data. After adjusting for confounding factors, genetic variant rs317386235, located between the genes PRKAR2B and PIK3CG exceeded the Bonferroni corrected significance threshold for ∆AXL. To complement the GWAS findings, an RNA sequencing transcriptomics analysis was performed, using retinal tissue from the treated and control eyes of chicks with high or low-susceptibility to myopia. This revealed 516 differentially-expressed genes, identified using a combination of three analysis tools. In order to discover more about the biological function underlying the GWAS and transcriptomics analysis results, pathway analyses were conducted. The pathway analysis implicated gene sets relating to circadian rhythms, extracellular matrix (ECM) and structural remodelling, energy generation, oxidative stress, glycometabolism and lipid metabolism.
9
Nagra, Manbir K. "Myopia : structural and functional correlates." Thesis, Aston University, 2010. http://publications.aston.ac.uk/10048/.
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Ocular dimensions are widely recognised as key variants of refractive error. Previously, accurate depiction of eye shape in vivo was largely restricted by limitations in the imaging techniques available. This thesis describes unique applications of the recently introduced 3-dimensional magnetic resonance imaging (MRI) approach to evaluate human eye shape in a group of young adult subjects (n=76) with a range of ametropia (MSE= -19.76 to +4.38D). Specific MRI derived parameters of ocular shape are then correlated with measures of visual function. Key findings include the significant homogeneity of ocular volume in the anterior eye for a range of refractive errors, whilst significant volume changes occur in the posterior eye as a function of ametropia. Anterior vs. posterior eye differences have also been shown through evaluations of equivalent spherical radius; the posterior 25% cap of the eye was shown to be relatively steeper in myopes compared to emmetropes. Further analyses showed differences in retinal quadrant profiles; assessments of the maximum distance from the retinal surface to the presumed visual axes showed exaggerated growth of the temporal quadrant in myopic eyes. Comparisons of retinal contour values derived from transformation of peripheral refraction data were made with MRI; flatter retinal curvature values were noted when using the MRI technique. A distinctive feature of this work is the evaluation of the relationship between ocular structure and visual function. Multiple aspects of visual function were evaluated through several vehicles: multifocal electroretinogram testing, visual field sensitivity testing, and the use of psychophysical methods to determine ganglion cell density. The results show that many quadrantic structural and functional variations exist. In general, the data could not demonstrate a significant correlation between visual function and associated measures of ocular conformation either within or between myopic and emmetropic groups.
10
Miyake, Masahiro. "Identification of myopia-associated WNT7B polymorphisms provides insights into the mechanism underlying the development of myopia." Kyoto University, 2015. http://hdl.handle.net/2433/202669.
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Julyan-Gudgeon, John Howard Ross. "Nitric oxide and form-deprivation myopia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0019/MQ48005.pdf.
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Edwards, Nicola R. "Oculomotor responses in emmetropia and myopia." Thesis, Aston University, 1994. http://publications.aston.ac.uk/14605/.
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It has been proposed that early-onset myopia (EOM) i.e. myopia onset before the age of 15 is primarily inherited whereas late-onset myopia (LOM) i.e. myopia onset after the age of 16 is induced by environmental factors, principally sustained near vision. No consensus exists as to which aspect of the near vision response; accommodation, vergence or their synergistic cross links promotes LOM development. Furthermore, the mechanism by which near vision could induce elongation of posterior chamber is obscure although there is evidence to show that ciliary muscle tone plays an important role. By comparing accommodation and vergence responses of emmetropes (EMMs), EOMs and LOMs under both open- and closed-loop conditions, this thesis aims to define further the oculomotor correlates of myopic development. A Canon Autoref R-1 optometer was used to measure accommodation responses while an Apple IIe controlled the flashed Maddox Rod sequence used when measuring vergence. Both techniques permitted open- and closed-loop measures to be obtained. The results presented demonstrate that it is unlikely that those individuals susceptible to LOM can be distinguished with regard to oculomotor responses or innervational characteristics of the ciliary muscle. The aetiology of LOM may be associated with ciliary muscle function but account needs to be taken of interactions between the ciliary muscle, choriod, sclera and introcular pressure and further research is necessary before those EMMs susceptible to LOM can be identified.
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Yoon, SangHo. "Essays on addiction, myopia, and inconsistency." Fairfax, VA : George Mason University, 2009. http://hdl.handle.net/1920/3449.
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Thesis (Ph.D.)--George Mason University, 2009.Vita: p. 154. Thesis director: Laurence R. Iannaccone. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Economics. Title from PDF t.p. (viewed June 10, 2009). Includes bibliographical references (p. 144-153). Also issued in print.
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Cyphers, Benjamin. "Side Effects of 0.01% Atropine." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu161701167574429.
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Xu, Shule, and 许舒乐. "Assessing the evidence for interventions that slow the progression of myopia: a literature review." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45174891.
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Fischer, Andy J. "Muscarinic mechanisms in myopia and ocular growth." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0018/NQ38467.pdf.
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Zayats, Tetyana. "Family study of high myopia : association studies." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54943/.
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High myopia (more severe than -6.00 Diopters) is one of the leading causes of blindness and vision impairment in the world. Its prevalence has rapidly been growing and the estimated number of myopic people worldwide is expected to be 2.5 billion by the year 2020. My experimental work covered three topics: (1) characterization of the quantity and quality of mouth wash-extracted DNA (2) genetic association studies, and (3) evaluation of an imprinting effect in high myopia. Mouthwash-derived DNA is an important source of human DNA for large-scale genetic studies. Thus, potential methods of DNA quantification (spectrophotometry, fluorometry, gel electrophoresis and qPCR) and quality assessment (gel electrophoresis and PCR) were evaluated. Regarding DNA quantification methods, fluorometry compared favorably to the gold-standard qPCR. DNA quality assessments revealed that -10% of collected buccal DNA samples were severely degraded—a phenomenon that was shown to be partly subject-specific. Myopia association studies were performed for: genes in MYP regions, the myocilin gene, the collagen type I alpha 1 gene and the collagen type II alpha 1 gene. These genes have been linked to myopia because of their function and/or previous positive findings. All tests were performed on a combined dataset of complex high myopia pedigrees and cases/controls, applying likelihood ratio statistics and Bonferroni correction to account for multiple testing. The results suggested that none of the genes examined have an important influence on susceptibility to high myopia. There is greater resemblance of refractive error between siblings than between parents and offspring, implying the possibility of imprinting in the aetiology of myopia. Thus, tests for imprinting were performed on "trio" pedigrees, applying Z-score and T2-test statistics and permutation to account for multiple testing. The results tentatively suggested that parent-of- origin effects and/or by maternal effects contribute to myopia development.
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Eames, Michael. "Institutional investor myopia, ownership, earnings, and returns /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/8768.
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Goris, K. G. "Orthokeratology, binocular co-ordination and myopia control." Thesis, London South Bank University, 2017. http://researchopen.lsbu.ac.uk/2246/.
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This work investigates two key questions: ; how myopia progression control treatments impact accommodation and binocular vision function and if accommodation and binocular vision function prior to myopia control interventions has any association with the efficacy of treatment. The work is made up of four main studies. Study 1 was a review and re-analysis of a previously completed study to investigate whether there are any possible associations between accommodation and binocular vision status prior to lens wear which may impact the myopia control efficacy of orthokeratology lens treatment. The data of 26 children were used. The study involved using an orthokeratology lens in one eye, with the contralateral eye used as a rigid gas permeable lens wearing control. Given the unusual nature of this modality, accommodation and binocular vision status was measured at baseline and monitored throughout the study to ensure that there were no adverse responses to lens wear. In a novel analysis of pre-existing data, the accommodation and binocular vision profiles of those participants that responded the best to orthokeratology lens treatment in terms of inhibiting ocular axial length growth were compared to those that did not respond to treatment. A similar comparison was made between those participants who progressed the most to the least in the control eye. Results from this analysis suggested that accommodation and binocular vision status prior to orthokeratology lens wear may be associated with treatment effect. Orthokeratology lens treatment worked best for myopia control when accommodative facility was higher and closer to population norms, AC/A ratio was lower and closer to population norms and accommodative lag was higher. None of these associations reached statistical significance, however further investigation appeared warranted. Interestingly, baseline near phoria did not appear to have an influence on response to treatment with orthokeratology lens wear. This is different to bifocal spectacle lens wear studies that show that initial near phoria has an impact on the efficacy of myopia control treatment. Study 2 was a review of clinical records of 37 children and young adult patients seen in two private optometric practices in Australia. Accommodation and binocular vision function prior to orthokeratology lens wear was compared to during lens wear in patients who were fitted with orthokeratology lenses between 2010 and 2012. The results of this study showed that there was a statistically significant change in mean near phoria in the exo direction with lens wear. Mean positive relative accommodation increased, mean negative relative accommodation decreased and accommodative facility increased. While the mean distance phoria remained unchanged there was a statistically significant reduction in the standard deviation of this variable. There was a slight reduction in mean lag of accommodation, but it failed to reach statistical significance. The study showed that the binocular vision status including accommodative and vergence measures changed during orthokeratology lens wear. The changes were in a direction closer to population norms. Study 3 was a prospective study of the impact of short-term orthokeratology lens wear on binocular vision in 12 young adults. Measurements of binocular vision status were taken at baseline and after one month of lens wear. The results of this study were similar to Study 2. There was no statistically significant change in mean near phoria. Distance accommodative facility increased. There was a slight, but not statistically significant, change in mean near accommodative facility Again, while there was no change in mean distance phoria, there was a significant reduction in the standard deviation of this variable. Additional variables of interest in this study included stereopsis, which was unchanged, and fixation disparity at distance and near which were unchanged. This short-term study showed that orthokeratology lens wear alters binocular vision status including accommodative and vergence measures. Again, the changes in binocular vision were in a direction closer to population norms. Study 4 was a record review of patients seen in the Myopia Control Clinic at the University of New South Wales, Sydney, Australia. The accommodation and binocular vision function of myopic children treated with orthokeratology lens wear or low dose atropine were reviewed. A total of 9 children treated with orthokeratology were followed for 3 to 6 months. Mean near phoria moved in the exo direction with orthokeratology lens wear and gradient AC/A ratio moved to more normal values with lens wear. There was an association between annualised axial length growth and gradient AC/A ratios and stereopsis, suggesting that baseline accommodation and binocular vision function may influence treatment. A total of 19 children were treated with low dose atropine and data were available from 3 to 6 months of treatment. Low dose atropine led to a small but not statistically significant decrease in amplitude of accommodation. Patients who were the worst responders to low dose atropine had lower baseline amplitude of accommodation compared to the best responders. Although speculative, the reduction in amplitude of accommodation may have a detrimental impact on the accommodation and binocular vision function and increase blur. Alternatively, those patients with high amplitude of accommodation may benefit from a subtle change in the accommodation and vergence relationship Both accommodation and vergence measures of binocular vision status appear to change with orthokeratology lens wear. The changes in binocular vision move in a direction closer to population norms; this is a novel finding of this thesis and is not reported elsewhere. Binocular vision that is abnormal has been associated with onset of myopia and progression. The changes in binocular vision associated with orthokeratology lens wear may contribute to the myopia progression control effect. Close monitoring of accommodation and binocular vision during myopia progression treatment is warranted.
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Chen, Jennifer C. "Autonomic imbalance - a precursor to myopia development?" Thesis, Queensland University of Technology, 2003. https://eprints.qut.edu.au/15803/1/Jennifer_Chen_Thesis.pdf.
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While prolonged nearwork is considered to be an environmental risk factor associated with myopia development, an underlying genetic susceptibility to nearwork-induced accommodative adaptation may be one possible mechanism for human myopia development. As the control of accommodation by the autonomic system may be one such genetically predetermined system, this research sought to investigate whether an anomaly of the autonomic control of accommodation may be responsible for myopia development and progression.
The emphasis of this work was determining the effect of altering the sympathetic input to the ciliary muscle on accommodation responses such as tonic accommodation and nearwork-induced accommodative adaptation in myopes and non-myopes. The first study of the thesis was based on observations of Gilmartin and Winfield (1995) which suggested that a deficit in the sympathetic inputs to the ciliary muscle may be associated with a propensity for myopia development. The effect of ß-antagonism with timolol application on accommodation characteristics was studied in different refractive error groups. Our results support the previous findings that a deficit of sympathetic facility during nearwork was not a feature of late-onset myopia. However it was found that classifying myopes according to stability of their myopia and their ethnic background was important and this allowed differentiation between accommodation responses and characteristics of the ciliary muscle autonomic inputs, with the greatest difference observed between Caucasian stable myopes and Asian progressing myopes.
Progressing myopes, particularly those with an Asian background, demonstrated enhanced susceptibility to nearwork-induced accommodative adaptation and this was suggested to result from a possible parasympathetic dominance and a relative sympathetic deficit to the ciliary muscle. In contrast, stable myopes, particularly those with an Asian background, demonstrated minimal accommodation changes following nearwork (counter-adaptation in some cases), and increased accommodative adaptation with ß-antagonism, suggesting sympathetic dominance as the possible autonomic accommodation control profile.
As ethnic background was found to be an important factor, a similar study was also conducted in a group of Hong Kong Chinese children to investigate if enhanced susceptibility to nearwork-induced changes in accommodation may explain in part the high prevalence of myopia in Hong Kong. Despite some minor differences in methodology between the two studies, the Hong Kong stable myopic children demonstrated counter-adaptive changes and greater accommodative adaptation with timolol, findings that were consistent with those of the adult Asian stable myopes. Both Asian progressing myopic children and adults also showed greater accommodative adaptation than the stable myopes and similar response profiles following ß-adrenergic antagonism. Thus a combination of genetically predetermined accommodation profiles that confer high susceptibility and extreme environmental pressures is a likely explanation for the increase in myopia over the past decades in Asian countries.
The hypothesis that a sympathetic deficit is linked to myopia was also investigated by comparing the effect of ß-stimulation with salbutamol, a ß-agonist, on accommodation with that of ß-antagonism using timolol. It was hypothesized that salbutamol would have the opposite effect of timolol, and that it would have a greater effect on subjects who demonstrated greater accommodative adaptation effects, i.e. the progressing myopes, compared to those who showed minimal changes in accommodation following nearwork. Consistent with the hypothesis, the effect of sympathetic stimulation with salbutamol application was only evident in the progressing myopes whom we hypothesized may have a parasympathetic dominance and a relative sympathetic deficit type of autonomic imbalance while it did not further enhance the rapid accommodative regression profile demonstrated by the stable myopes.
Characteristics of the convergence system and the interaction between accommodation and convergence were also investigated in the Hong Kong children. No significant differences in response AC/A ratios between the emmetropic, stable and progressing myopic children were found and it was concluded that elevated AC/A ratios were not associated with higher myopic progression rate in this sample of Hong Kong children. However, ß-adrenergic antagonism with timolol application produced a greater effect on accommodative convergence (AC) in stable myopic children who presumably have a more adequate, robust sympathetic input to the ciliary muscle, but had little effect on AC of progressing myopic children. This finding again points to the possibility that the autonomic control of the accommodation and convergence systems may be different between stable and progressing myopia.
The primary contribution of this study to the understanding of myopia development is that differences in the autonomic control of the ciliary muscle may be responsible for producing anomalous accommodation responses. This could have significant impact on retinal image quality and thus results in myopia development. This knowledge may be incorporated into computer models of accommodation and myopia development and provides scope for further investigation of the therapeutic benefits of autonomic agents for myopia control.
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Chen, Jennifer C. "Autonomic Imbalance - a Precursor to Myopia Development?" Queensland University of Technology, 2003. http://eprints.qut.edu.au/15803/.
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While prolonged nearwork is considered to be an environmental risk factor associated with myopia development, an underlying genetic susceptibility to nearwork-induced accommodative adaptation may be one possible mechanism for human myopia development. As the control of accommodation by the autonomic system may be one such genetically predetermined system, this research sought to investigate whether an anomaly of the autonomic control of accommodation may be responsible for myopia development and progression. The emphasis of this work was determining the effect of altering the sympathetic input to the ciliary muscle on accommodation responses such as tonic accommodation and nearwork-induced accommodative adaptation in myopes and non-myopes. The first study of the thesis was based on observations of Gilmartin and Winfield (1995) which suggested that a deficit in the sympathetic inputs to the ciliary muscle may be associated with a propensity for myopia development. The effect of ß-antagonism with timolol application on accommodation characteristics was studied in different refractive error groups. Our results support the previous findings that a deficit of sympathetic facility during nearwork was not a feature of late-onset myopia. However it was found that classifying myopes according to stability of their myopia and their ethnic background was important and this allowed differentiation between accommodation responses and characteristics of the ciliary muscle autonomic inputs, with the greatest difference observed between Caucasian stable myopes and Asian progressing myopes. Progressing myopes, particularly those with an Asian background, demonstrated enhanced susceptibility to nearwork-induced accommodative adaptation and this was suggested to result from a possible parasympathetic dominance and a relative sympathetic deficit to the ciliary muscle. In contrast, stable myopes, particularly those with an Asian background, demonstrated minimal accommodation changes following nearwork (counter-adaptation in some cases), and increased accommodative adaptation with ß-antagonism, suggesting sympathetic dominance as the possible autonomic accommodation control profile. As ethnic background was found to be an important factor, a similar study was also conducted in a group of Hong Kong Chinese children to investigate if enhanced susceptibility to nearwork-induced changes in accommodation may explain in part the high prevalence of myopia in Hong Kong. Despite some minor differences in methodology between the two studies, the Hong Kong stable myopic children demonstrated counter-adaptive changes and greater accommodative adaptation with timolol, findings that were consistent with those of the adult Asian stable myopes. Both Asian progressing myopic children and adults also showed greater accommodative adaptation than the stable myopes and similar response profiles following ß-adrenergic antagonism. Thus a combination of genetically predetermined accommodation profiles that confer high susceptibility and extreme environmental pressures is a likely explanation for the increase in myopia over the past decades in Asian countries. The hypothesis that a sympathetic deficit is linked to myopia was also investigated by comparing the effect of â-stimulation with salbutamol, a ß-agonist, on accommodation with that of ß-antagonism using timolol. It was hypothesized that salbutamol would have the opposite effect of timolol, and that it would have a greater effect on subjects who demonstrated greater accommodative adaptation effects, i.e. the progressing myopes, compared to those who showed minimal changes in accommodation following nearwork. Consistent with the hypothesis, the effect of sympathetic stimulation with salbutamol application was only evident in the progressing myopes whom we hypothesized may have a parasympathetic dominance and a relative sympathetic deficit type of autonomic imbalance while it did not further enhance the rapid accommodative regression profile demonstrated by the stable myopes. Characteristics of the convergence system and the interaction between accommodation and convergence were also investigated in the Hong Kong children. No significant differences in response AC/A ratios between the emmetropic, stable and progressing myopic children were found and it was concluded that elevated AC/A ratios were not associated with higher myopic progression rate in this sample of Hong Kong children. However, ß-adrenergic antagonism with timolol application produced a greater effect on accommodative convergence (AC) in stable myopic children who presumably have a more adequate, robust sympathetic input to the ciliary muscle, but had little effect on AC of progressing myopic children. This finding again points to the possibility that the autonomic control of the accommodation and convergence systems may be different between stable and progressing myopia. The primary contribution of this study to the understanding of myopia development is that differences in the autonomic control of the ciliary muscle may be responsible for producing anomalous accommodation responses. This could have significant impact on retinal image quality and thus results in myopia development. This knowledge may be incorporated into computer models of accommodation and myopia development and provides scope for further investigation of the therapeutic benefits of autonomic agents for myopia control.
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Yang, Chih Huang. "Vitamin D in dry eye and myopia." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/113952/1/Chih%20Huang_Yang_Thesis.pdf.
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Vitamin D is important to human health with a variety of systemic diseases linked to vitamin D deficiency. The effect of a two month treatment of a vitamin D oral supplement on the ocular surface in older people with dry eye and on binocular vision in younger adults with short-sightedness was assessed. Vitamin D had a beneficial effect on symptoms of dry eye in older people and improved the accommodation function in younger adults. This work suggests that the development of vitamin D eye drops might be useful for these conditions.
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Kaphle, Dinesh. "Ciliary muscle function and accommodation in myopia." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/212645/1/Dinesh_Kaphle_Thesis.pdf.
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Myopia (short-sightedness) is a progressive condition often associated with near work. This research investigated the accommodation system during treatment with myopia-control multifocal spectacles. Meta-analysis of prior work showed that effectiveness of multifocal spectacles reduces with time, even after the first six months. During accommodation, the anterior ciliary muscle thickens, and its overall length reduces, in both emmetropes and myopes. Myopes have the larger lags of accommodation. Multifocal spectacles initially decrease the lags, but over-time the lags increase, and upgrading addition power by 0.50D restores the initial effect. Modifications to add power can sustain the treatment effect for longer periods.
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Jonuscheit, Sven. "Characteristics of the cornea in the myopic human eye." Thesis, Glasgow Caledonian University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492392.
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The objective of the present studies was to assess whether there were predictable differences in the thickness of the human cornea in relation to stable manifest refractive error using a scanning slit optical topography method (Orbscan II).
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Berntsen, David A. "Accommodative lag, peripheral aberrations, and myopia in children." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243829481.
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Walline, Jeffrey Jay. "The contact lens and myopia progression (clamp) study /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486546889380302.
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McTrusty, Alice Davidson. "An investigation of visual function in axial myopia." Thesis, Glasgow Caledonian University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.688306.
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Cheng, Desmond. "Bifocal lens control of myopia progression in children." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/29688/2/Desmond_Cheng_Thesis.pdf.
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This research investigated underlying issues that were critical to the success of the bifocal trial and comprised of three studies. The first study evaluated if Chinese-Canadian children were suitable subjects for the bifocal trial. The high prevalence of myopia in Chinese children suggests that genetic input plays a role in myopia development, but the rapid increase in prevalence over the last few decades indicates environmental factors are also important. Since this bifocal trial was conducted in Canada, this work aimed to determine whether Chinese children who had migrated to Canada would still have high myopia prevalence and a high rate of myopia progression. The second study determined the optimal bifocal lens power for myopia treatment and the effect of incorporating base-in prism into the bifocal. In the majority of published myopia control studies, the power of the prescribed near addition was usually predetermined in the belief that the near addition would always help to improve the near focus. In fact, the effect of near addition on the accommodative error might be quite different even for individuals in which the same magnitude of accommodation lag had been measured. Therefore, this work was necessary to guide the selection of bifocal and prism powers most suitable for the subsequent bifocal trial. The third study, the ultimate goal of this research, was to conduct a longitudinal clinical trial to determine if bifocals and prismatic bifocals could control myopia progression in children.
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Cheng, Desmond. "Bifocal lens control of myopia progression in children." Queensland University of Technology, 2008. http://eprints.qut.edu.au/29688/.
Full textAbstract:
This research investigated underlying issues that were critical to the success of the bifocal trial and comprised of three studies. The first study evaluated if Chinese-Canadian children were suitable subjects for the bifocal trial. The high prevalence of myopia in Chinese children suggests that genetic input plays a role in myopia development, but the rapid increase in prevalence over the last few decades indicates environmental factors are also important. Since this bifocal trial was conducted in Canada, this work aimed to determine whether Chinese children who had migrated to Canada would still have high myopia prevalence and a high rate of myopia progression. The second study determined the optimal bifocal lens power for myopia treatment and the effect of incorporating base-in prism into the bifocal. In the majority of published myopia control studies, the power of the prescribed near addition was usually predetermined in the belief that the near addition would always help to improve the near focus. In fact, the effect of near addition on the accommodative error might be quite different even for individuals in which the same magnitude of accommodation lag had been measured. Therefore, this work was necessary to guide the selection of bifocal and prism powers most suitable for the subsequent bifocal trial. The third study, the ultimate goal of this research, was to conduct a longitudinal clinical trial to determine if bifocals and prismatic bifocals could control myopia progression in children.
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Chwee, Hong Yeo. "The role of near adaptation in myopia development." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48207/1/Yeo_Chwee_Hong_Thesis.pdf.
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Prolonged near work is associated with myopia development in children and young adults but the reason underlying this association is unknown. Two potentially important factors are the near work induced ocular adaptations of contrast and accommodative adaptation. This study measured the degrees of contrast and accommodative adaptation during and following reading in myopic and emmetropic children and young adults in Singapore, where myopia is highly prevalent. Reading caused significantly greater contrast and accommodative adaptations in myopic children and myopic young adults compared to that measured in emmetropes of comparable ages. The adaptations were greater in magnitude in children than young adults, suggesting that children are more susceptible to ocular changes induced by reading and thus are potentially at greater risk of adverse refractive outcomes from these adaptations. In addition to the magnitude of the adaptations the regression time of these adaptations, (i.e. their durations) are also important. Longer accommodative adaptation regression times were measured for myopic children than for emmetropic children. Although the regression of contrast adaptation was not measured, its duration may likewise be important. The refractive effects of both of these adaptations are likely to be cumulative across the day and this could promote myopia in susceptible individuals performing considerable amounts of near work. Whether the type of text read affected the magnitude of the adaptations was also explored. Given the high prevalence of myopia in Chinese children and the fact that Chinese text is more complicated to write than English text, it was hypothesized that Chinese text would induce greater adaptation. However, both Chinese and English text produced similar amounts of accommodative and contrast adaptation in young adult subjects. We propose that children who spend prolonged periods reading at a young age are most vulnerable to near work induced adaptations and hence near work induced myopia. Both Chinese and English texts produce these effects and we propose that these adaptations are likely to occur for all types of common reading texts.
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Zhou, Nanyu. "Cone signals and activity in myopia and emmetropia." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/63463/1/Nanyu_Zhou_Thesis.pdf.
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Myopia (short-sightedness) is a common ocular disorder of children and young adults. Studies primarily using animal models have shown that the retina controls eye growth and the outer retina is likely to have a key role. One theory is that the proportion of L (long-wavelength-sensitive) and M (medium-wavelength-sensitive) cones is related to myopia development; with a high L/M cone ratio predisposing individuals to myopia. However, not all dichromats (persons with red-green colour vision deficiency) with extreme L/M cone ratios have high refractive errors. We predict that the L/M cone ratio will vary in individuals with normal trichromatic colour vision but not show a systematic difference simply due to refractive error. The aim of this study was to determine if L/M cone ratios in the central 30° are different between myopic and emmetropic young, colour normal adults.
Information about L/M cone ratios was determined using the multifocal visual evoked potential (mfVEP). The mfVEP can be used to measure the response of visual cortex to different visual stimuli. The visual stimuli were generated and measurements performed using the Visual Evoked Response Imaging System (VERIS 5.1). The mfVEP was measured when the L and M cone systems were separately stimulated using the method of silent substitution. The method of silent substitution alters the output of three primary lights, each with physically different spectral distributions to control the excitation of one or more photoreceptor classes without changing the excitation of the unmodulated photoreceptor classes. The stimulus was a dartboard array subtending 30° horizontally and 30° vertically on a calibrated LCD screen. The m-sequence of the stimulus was 215-1. The N1-P1 amplitude ratio of the mfVEP was used to estimate the L/M cone ratio.
Data were collected for 30 young adults (22 to 33 years of age), consisting of 10 emmetropes (+0.3±0.4 D) and 20 myopes (–3.4±1.7 D). The stimulus and analysis techniques were confirmed using responses of two dichromats. For the entire participant group, the estimated central L/M cone ratios ranged from 0.56 to 1.80 in the central 3°-13° diameter ring and from 0.94 to 1.91 in the more peripheral 13°-30° diameter ring. Within 3°-13°, the mean L/M cone ratio of the emmetropic group was 1.20±0.33 and the mean was similar, 1.20±0.26, for the myopic group. For the 13°-30° ring, the mean L/M cone ratio of the emmetropic group was 1.48±0.27 and it was slightly lower in the myopic group, 1.30±0.27. Independent-samples t-test indicated no significant difference between the L/M cone ratios of the emmetropic and myopic group for either the central 3°-13° ring (p=0.986) or the more peripheral 13°-30° ring (p=0.108).
The similar distributions of estimated L/M cone ratios in the sample of emmetropes and myopes indicates that there is likely to be no association between the L/M cone ratio and refractive error in humans.
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Martinez, Aldo A. Optometry & Vision Science Faculty of Science UNSW. "On and off-axis monochromatic aberrations and myopia in young children." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/33676.
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Purpose: To study ???on??? and ???off-axis??? wavefront aberration of eyes of children and to determine the relationship with refractive error development. Methods: On and off-axis ocular aberrations of cyclopleged eyes of children (mostly 12 year olds) were measured and compared to data obtained from a group of mostly 6 year old children. Only data from the right eyes were analysed (pupil diameter=5 mm) and categorised into refractive error groups based on ???M???. Differences in ???on??? and ???off-axis??? aberrations between refractive and ethnic groups were analysed using univariate and multivariate analyses of variance with adjustment for multiple comparisons. Off-axis refraction was analysed using skiagrams and mean relative spherical equivalent. Results: Data from 1,636 12 year old children (mean age 12.6 ?? 0.4 years) was analysed. Lower order aberrations were the largest and higher order aberrations contributed to only 25% of the wavefront. There were no differences in the amount of total higher orders between refractive groups. Of the individual higher orders, spherical aberration was greater in hyperopic eyes (0.07 ?? 0.06 ??m) in comparison to emmetropic and myopic eyes (0.05 ?? 0.04 ??m and 0.05 ?? 0.04 ??m) (p<0.001). Myopic eyes had more positive values of Z(3,-1) (p<0.05). Similar results were obtained for the 1,364 6 year old children (mean age 6.7 ??? 0.4 years). Despite East Asian children being more myopic than other ethnic groups (p<0.01), there were no differences in higher orders except for low hyperopic East Asian eyes presenting with higher levels of positive spherical aberrations (p<0.001). When compared to the fovea, off-axis myopic eyes had hyperopia (0.55 to 1.66 D) and emmetropes and hyperopes had myopia (0.10 to -2.00 D). Astigmatism and defocus were the dominant off-axis aberrations. The magnitude of higher order aberrations (mostly 3rd orders) increased with eccentricity but was similar across refractive error groups. Conclusions: Myopic eyes do not have abnormal or excessive levels of on and off-axis higher order aberrations but had patterns of off-axis refraction that may be associated with progression. Considerable inter-subject variability in higher order aberrations was seen for all refractive groups. However, their magnitude was small and suggests that any impact on the optical quality of the eye is negligible.
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Knapp, Jonelle. "Effect of Peripheral Defocus on Retinal Function via Mathematical Modeling of the Multifocal Electroretinogram Response." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574626289219112.
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Kearney, Stephanie. "Myopia : the association between environmental factors and refractive error." Thesis, Ulster University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725340.
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Feltham, Mark Hayes Optometry & Vision Science Faculty of Science UNSW. "Factors which affect refractive outcome following LASIK for myopia." Awarded by:University of New South Wales. School of Optometry and Vision Science, 2004. http://handle.unsw.edu.au/1959.4/20800.
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Purpose: To improve the predictability, accuracy and stability of laser in-situ keratomileusis (LASIK), by evaluating the clinical, procedural and tissue response factors that affect refractive outcomes. Methods: Myopic LASIK surgeries (n=5,978) were carried out using the Technolas planoscan and Nidek EC-5000 excimer lasers. Clinical variables associated with a refractive outcome of within ??0.50 D of the target were identified using regression analysis. Possible procedural variations such as the timing of the procedure and accuracy of both the chosen keratome and excimer laser were evaluated. The predictability and accuracy of the ablation was assessed by measuring changes in corneal thickness during and after the procedure. Factors influencing the stability of refractive outcome were assessed. Results: Clinical factors associated with a refractive outcome of within ??0.50 D of the target included; corrections less than 5.00 DS (OR 0.21x, 95% CI 0.11-0.40x compared with corrections over -5.00 DS[referent]), patients younger than 40 years (patients over 50 OR 8.27x, 95% CI 3.41-20.03x, patients 40 to 50 years OR 1.93x, 95% CI 0.96-3.90x, compared with patients under 40[referent]) and average pre-operative curvatures between 43.50 and 45.50D (OR 0.39x, 95% CI 0.18-0.83 compared with curvatures of less than 43.50D [referent]). Refractive stability was improved using optic zone sizes between 5.5-6.0 mm, reduced myopic corrections, flatter pre-operative corneal curvatures and thicker corneal flaps (R??=25%, p<0.001). Procedural factors associated with poorer outcomes included: thinner measured flap thickness, deeper ablations and the use of the automated corneal shaper (ACS) microkeratome with a novice surgical team (R??=34%, p < 0.001). Delaying the ablation from 20 to 90 seconds (s) after flap lift was associated with a more stable refractive outcome at three months (p=0.017). In the 90 s following flap lift, the cornea thinned by 5??3%. The ablation rate per scan varied between procedures, however, the effect on refractive outcome was small (r=0.15, p=0.267). Changes in central corneal thickness indicated refractive stability (p=0.039). Conclusions: Applying the optimal clinical and procedural factors as described afforded a refractive outcome in a further 8% of cases, resulting in 94% to 96% of cases within ??0.50 DS of target. Refractive predictability was limited due to the inability of the keratome to produce a consistent corneal flap thickness and unexpected changes in corneal thickness. The accuracy of refractive outcome will decrease with larger ablations. The degree of refractive inaccuracy with high refractive corrections (> -10.00 D) can be over 1.00 D.
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Anstice, Nicola. "Dual-focus inhibition of myopia evaluation in New Zealand." Thesis, University of Auckland, 2009. http://hdl.handle.net/2292/5613.
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Whole document restricted until 01/2011, see Access Instructions file below for details of how to access the print copy.Purpose: The Dual-focus Inhibition of Myopia Evaluation in New Zealand (DIMENZ) clinical trial tests the efficacy of myopic retinal defocus in slowing axial myopia progression. Methods: Dual-focus (DF) soft contact lenses were designed having a central zone correcting refractive error and peripheral treatment zones that caused 2.00D of simultaneous myopic retinal defocus. Children (12-14 yrs, n = 40, mean refractive error = -2.70D) were fitted with a DF lens in one eye and a single vision distance (SVD) lens in the fellow eye. After 10 mo. wear, lens assignment was swapped between eyes and the lenses worn for a further 10 mo. Accommodation was measured using an open-field autorefractor. Myopia was monitored using cycloplegic autorefraction and partial coherence interferrometry every 5 mo. Results: For DF lens-wearing eyes mean (± 1 SD) acuity was 99.85 ± 3.53) and for SV lens-wearing eyes 100.20 ± 2.87 (p = 0.209). After 10 months of CL wear mean (± 1 SD) increase in myopia and axial length in eyes wearing the DF lens (-0.441 ± 0.326 & 0.110 ± 0.084) were significantly less (p < 0.001) than in eyes wearing the SVD lens (-0.677 ± 0.405 & 0.218 ± 0.089). Thus, DF lenses had a 12 month adjusted treatment effect of 0.28D & 0.13 mm. Accommodative response was measured through the SVD lens and through a single vision near (SVN) lens (+2.50 D add) that reduced the accommodative demand to zero. When children changed their gaze from 4 m to 40 cm, accommodation increased by 1.80 ± 0.37 D when wearing a DF lens with a SVD lens and by 1.62 ± 0.59 with a DF and SVN contact lens (no significant difference, p = 0.21). Conclusion: Myopia progression is slowed significantly in eyes wearing DF lenses. This suggests that a myopically defocused image, even when presented to the retina simultaneously with a clear image, acts to slow myopia progression in children. DF lenses provide normal acuity and do not alter accommodative response, so provide myopic retinal defocus at distance and near.
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Cabello, Carlos S. "Droning on: American strategic myopia toward unmanned aerial systems." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/38890.
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Approved for public release; distribution is unlimited.Throughout the past decade of wars, the U.S. has deployed unmanned aerial systems, commonly referred to as drones, from Africa to Asia collecting intelligence and targeting adversaries. The nation now stands at a crossroad seeking to develop future American drone policy against an evolving threat while at the same time shaping global norms. The past decade of American drone use focused on short-term benefits, intelligence collection and lethal targeting, rather than on the long-term consequences of technology diffusion, or ethical and legal frameworks. Myopic drone strategies threaten to establish a global precedent that could undermine the stability of international relations, as state and non-state actors (SANSA) have begun to build, arm, and operate lethal unmanned systems at an alarming rate. Unmanned technology development and usage is outpacing international norms, regulations, and policies. These systems will usher in an era of unrestricted drone usage unless international regulations and standards are developed. This thesis examines whether American drone strategy is myopic and whether it is creating a dangerous international precedent. A qualitative analysis will identify the short-term benefits and long-term consequences of U.S. drone strategy, focusing on unmanned technology diffusion, ethical justifications, and legal frameworks. Examining American drone strategy can help explain why a myopic policy may be beneficial in the short-term, yet may increase threats to national interests in the long-term. The thesis concludes with an assessment of whether strategic myopia has already set a dangerous international precedent, which SANSA will use to justify their future drone programs.
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Chen, Yen-Po. "Role of genetics in susceptibility to environmentally-induced myopia." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/55049/.
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Myopia is a common ocular disorder with complex and yet unidentified causes. Studies in animal models of myopia have revealed substantial variation in the degree of myopia induced by a uniform regimen of visual manipulation. This study investigated the role of genetics on susceptibility to environmentally-induced myopia by means of a selective breeding experiment. Chicks with high or low susceptibility to monocular form deprivation (FD) were selected from an outbred population that showed considerable variation in the response to FD. After two rounds of selection, the High and Low susceptibility selected lines exhibited an evident divergence in their ocular responses to FD. Chicks from the High line developed twice the degree of myopia compared to those from the Low line. This difference was not due to visual disability or immaturity of the visual system in Low line chicks. Thus, susceptibility to form deprivation in chicks has a strong genetic component. In estimating the heritability, approximately 50% of the variation in the chicks' susceptibility to FD-induced myopia was attributable to additive genetic effects. However, the genetic variants that control the normal variation in eye size appear to be distinct from the variants that determine susceptibility to FD due to no evidence of pleiotropic genetic effects between these traits. When chicks from the High and Low lines were tested for their responses to lens- induced visual defocus, a significant difference between the two selected lines was observed for minus lens wear, but not for plus lens wear. Thus, there must be some shared mechanism(s) in the ocular responses to FD and minus lens wear, but different mechanisms in the responses to plus lens wear and FD. Compared to the chicken, the mouse model of myopia has the advantages of a closer evolutionary relationship to humans and features of primate myopia. Using a novel swept-source OCT system, it was found that OCT showed good repeatability and accuracy in measuring axial ocular components in mouse. In addition, axial ocular components in mice were found to be mainly controlled by additive genetic effects.
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Seidel, Dirk. "Retinotopic and spatiotopic accommodation responses in emmetropia and myopia." Thesis, Glasgow Caledonian University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289522.
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The incidence of myopia has been rising steadily over the last century. Today the prevalence of the condition ranges from under 1% in remote parts of the world to over 90% in some highly industrialised urban areas. The associated pathological risk factors in connection with the continuous increase in the number of myopic individuals have put increasing pressure on the health and social systems worldwide. The aetiology and course of the condition has therefore always been of interest to patients, ophthalmic practitioners and researchers alike. Reduced accommodation responses as a precursor to or even a cause of myopia have been proposed for a long time. Increased lags of accommodation found in myopes, causing a reduction in the quality of the retinal image, seem to support animal models, which have suggested that retinal defocus if present over longer periods of time can lead to the elongation of the globe. In this work different aspects of the accommodation response have been studied in emmetropes (EMM), early-onset (EOM) and late-onset myopes (LOM) under a variety of viewing conditions. The steady state accommodation response, the microfluctuations of accommodation and accommodation step responses of different magnitudes (1-dioptre and 2-dioptre steps) were examined for retinotopic (eye referenced) and spatiotopic (body-referenced) viewing conditions. Retinotopic conditions involved viewing targets in Badal systems. Spatiotopic viewing involved real targets presented in free space thus providing size and proximity cues to the accommodation controller. The free space targets were viewed monocularly and binocularly, which examined the importance of vergence accommodation for the different refractive groups. Steady state accommodation responses were found to be similar across the refractive groups for all viewing conditions. LOM subjects however, showed higher variability of their steady-state response in Badal systems but not in free space viewing. LOMs also demonstrated significantly greater microfluctuations of accommodation in the retinotopic condition, while the fluctuations were of similar magnitude for all groups for free space viewing. While EMMs and EOMs responded promptly and quickly to step changes in target vergence in both retinotopic and spatiotopic conditions, LOMs showed slower reaction and response times in the blur-only environment. Analysis of the response rate (percentage of step changes made for a given number of stimulus changes) revealed that some LOMs hesitated to adjust their accommodation to small step changes in target distance when only retinotopic cues were present. Real targets alleviated these differences between the groups and increased the LOMs response rate considerably. The minimum blur threshold of the accommodation controller was examined presenting sinusoidal stimuli of very small dioptric magnitude in a Badal system. Fourier analysis revealed that EMMs and EOMs responded to stimuli < 0.15 D while LOMs required stimuli > 0.3 D. Cross-correlating the findings of the different experiments showed that LOMs with inaccurate and more variable accommodation responses in retinotopic conditions improve substantially with the introduction of real world targets, whereas EMMs and EOMs with sufficient blur accommodation show no significant improvement. The findings indicate a deficient blur processing in LOMs but demonstrate that there are no significant differences in accommodation performance between emmetropes and myopes in real world conditions. The implications of the findings on the development and progression of myopia are discussed at the end of the thesis.
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McVey, Mary Elizabeth. "The Bifocal Lens Inhibition of Myopia Progression (BLIMP) Study." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275489282.
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Korsan, Jenna M. "Soft Multifocal Contact Lenses for Myopia Control in Children." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429012620.
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Patel, Hetal. "Biomechanical aspects of the anterior segment in human myopia." Thesis, Aston University, 2011. http://publications.aston.ac.uk/14871/.
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The thesis investigates the relationship between the biomechanical properties of the anterior human sclera and cornea in vivo using Schiotz tonometry (ST), rebound tonometry (RBT, iCare) and the Ocular Response Analyser (ORA, Reichert). Significant differences in properties were found to occur between scleral quadrants. Structural correlates for the differences were examined using Partial Coherent Interferometry (IOLMaster, Zeiss), Optical Coherent tomography (Visante OCT), rotating Scheimpflug photography (Pentacam, Oculus) and 3-D Magnetic Resonance Imaging (MRI). Subject groups were employed that allowed investigation of variation pertaining to ethnicity and refractive error. One hundred thirty-five young adult subjects were drawn from three ethnic groups: British-White (BW), British-South-Asian (BSA) and Hong-Kong-Chinese (HKC) comprising non-myopes and myopes. Principal observations: ST demonstrated significant regional variation in scleral resistance a) with lowest levels at quadrant superior-temporal and highest at inferior-nasal; b) with distance from the limbus, anterior locations showing greater resistance. Variations in resistance using RBT were similar to those found with ST; however the predominantly myopic HKC group had a greater overall mean resistance when compared to the BW-BSA group. OCT-derived scleral thickness measurements indicated the sclera to be thinner superiorly than inferiorly. Thickness varied with distance from the corneolimbal junction, with a decline from 1 to 2 mm followed by a successive increase from 3 to 7 mm. ORA data varied with ethnicity and refractive status; whilst axial length (AL) was associated with corneal biometrics for BW-BSA individuals it was associated with IOP in the HKC individuals. Complex interrelationships were found between ORA Additional-Waveform-Parameters and biometric data provided by the Pentacam. OCT indicated ciliary muscle thickness to be greater in myopia and more directly linked to posterior ocular volume (from MRI) than AL. Temporal surface areas (SAs, from MRI) were significantly smaller than nasal SAs in myopic eyes; globe bulbosity (from MRI) was constant across quadrants.
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Harper, Justine. "Ocular biometric correlates of early-and late-onset myopia." Thesis, Aston University, 2001. http://publications.aston.ac.uk/14536/.
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Myopia is a refractive condition and develops because either the optical power of the eye is abnormally great or the eye is abnormally long, the optical consequences being that the focal length of the eye is too short for the physical length of the eye. The increase in axial length has been shown to match closely the dioptric error of the eye, in that a lmm increase in axial length usually generates 2 to 3D of myopia. The most common form of myopia is early-onset myopia (EO M) which occurs between 6 to 14 years of age. The second most common form of myopia is late-onset myopia (LOM) which emerges in late teens or early twenties, at a time when the eye should have ceased growing. The prevalence of LOM is increasing and research has indicated a link with excessive and sustained nearwork. The aim of this thesis was to examine the ocular biometric correlates associated with LOM and EOM development and progression. Biometric data was recorded on SO subjects, aged 16 to 26 years. The group was divided into 26 emmetropic subjects and 24 myopic subjects. Keratometry, corneal topography, ultrasonography, lens shape, central and peripheral refractive error, ocular blood flow and assessment of accommodation were measured on three occasions during an ISmonth to 2-year longitudinal study. Retinal contours were derived using a specially derived computer program. The thesis shows that myopia progression is related to an increase in vitreous chamber depth, a finding which supports previous work. The myopes exhibited hyperopic relative peripheral refractive error (PRE) and the emmetropes exhibited myopic relative PRE. Myopes demonstrated a prolate retinal shape and the retina became more prolate with myopia progression. The results show that a longitudinal, rather than equatorial, increase in the posterior segment is the principal structural correlate of myopia. Retinal shape, relative PRE and the ratio of axial length to corneal curvature have been indicated, in this thesis, as predictive factors for myopia onset and development. Data from this thesis demonstrates that myopia progression in the LOM group is the result of an increase in anterior segment power, owing to an increase in lens thickness, in conjunction with posterior segment elongation. Myopia progression in the EOM group is the product of a long posterior segment, which over-compensates for a weak anterior segment power. The weak anterior segment power in the EOM group is related to a combination of crystalline lens thinning and surface flattening. The results presented in this thesis confirm that posterior segment elongation is the main structural correlate in both EOM and LOM progression. The techniques and computer programs employed in the thesis are reproducible and robust providing a valuable framework for further myopia research and assessment of predictive factors.
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Шищук, Володимир Дмитрович, Владимир Дмитриевич Шищук, Volodymyr Dmytrovych Shyshchuk, А. Ю. Солод, Михайло Олексійович Чумак, Михаил Алексеевич Чумак, and Mykhailo Oleksiiovych Chumak. "Дослідження стану зорових функцій у хворих з дистрофічною формою міопії після проведення склеропластичних та вазореконструктивних операцій." Thesis, Видавництво СумДУ, 2009. http://essuir.sumdu.edu.ua/handle/123456789/6176.
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Alderson, Alison. "Structural and functional aspects of myopia in young adults : an investigation of nearwork-induced transient myopia and accommodation in relation to refractive stability." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5518.
Full textAbstract:
This thesis has investigated nearwork-induced transient myopia and accommodation responses in relation to refractive stability, multichromatic stimuli and orthokeratology. Five individual studies have been carried out. Initially an investigation into the temporal and dioptric aspects of nearwork-induced transient myopia was undertaken, suggesting that increased task duration does not increase the level, or slow the regression of post-task NITM, however an increase in the dioptric demand of the task does. In the second study, a longitudinal myopia progression study, these findings were related to short term myopia progression. The third investigation demonstrates the feasibility of measuring the biometric correlates of nearwork-induced transient myopia using a low coherence reflectometry device (LenStar, Haag Streit Koeniz, Switzerland). Fourthly, a comparison of the differences between static and dynamic accommodative responses, microfluctuations and nearwork-induced transient myopia produced when viewing a black/white target as oppose to a red/blue target has suggested the possibility of four accommodative responses to this multichromatic stimulus. Further investigation will be necessary to investigate if any of these response types are related to myopia progression. 2 The final study investigates the effect of two different designs of orthokeratology contact lenses (C5 and polynomial) on visual function. It appears to be the case that although the polynomial lens design has a larger refractive effect than the C5 lens it reduces both high and low contrast corrected visual acuity to a greater extent. The higher the baseline mean spherical equivalent refractive error the larger the detrimental effect.
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Alderson, Alison J. "Structural and functional aspects of myopia in young adults. An investigation of nearwork-induced transient myopia and accommodation in relation to refractive stability." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5518.
Full textAbstract:
This thesis has investigated nearwork-induced transient myopia and accommodation responses in relation to refractive stability, multichromatic stimuli and orthokeratology. Five individual studies have been carried out. Initially an investigation into the temporal and dioptric aspects of nearwork-induced transient myopia was undertaken, suggesting that increased task duration does not increase the level, or slow the regression of post-task NITM, however an increase in the dioptric demand of the task does. In the second study, a longitudinal myopia progression study, these findings were related to short term myopia progression.
The third investigation demonstrates the feasibility of measuring the biometric correlates of nearwork-induced transient myopia using a low coherence reflectometry device (LenStar, Haag Streit Koeniz, Switzerland).
Fourthly, a comparison of the differences between static and dynamic accommodative responses, microfluctuations and nearwork-induced transient myopia produced when viewing a black/white target as oppose to a red/blue target has suggested the possibility of four accommodative responses to this multichromatic stimulus. Further investigation will be necessary to investigate if any of these response types are related to myopia progression.
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The final study investigates the effect of two different designs of orthokeratology contact lenses (C5 and polynomial) on visual function. It appears to be the case that although the polynomial lens design has a larger refractive effect than the C5 lens it reduces both high and low contrast corrected visual acuity to a greater extent. The higher the baseline mean spherical equivalent refractive error the larger the detrimental effect.College of Optometrists
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Parekh, Rishabh. "Aggregated Versus Disaggregated Forward Looking Information: Effects on Risk Taking." Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/cmc_theses/398.
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In previous research, aggregation of returns has been found as a way to counteract the risk averse behavior that is the result of investors' myopia. This paper expands the study of aggregation by analyzing its effect on forward looking probabilities. Namely, through the disaggregation of future information, subjects become myopic and trade with varying risk preferences. In an experimental market, subjects trading securities with disaggregated forward looking information are found to 'buy high and sell low', while subjects trading the same securities, but with aggregated information, trade with more consistent risk preferences.
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Chui, Toco Yuen Ping. "Influence of myopia on cone packing density and foveal morphology." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3386667.
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Thesis (Ph.D.)--Indiana University, School of Optometry, 2009.Title from PDF t.p. (viewed on Jul 20, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7503. Adviser: Stephen A. Burns.
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Backhouse, Simon. "Induced myopia in the guinea pig: scleral myofibroblasts and biomechanics." Thesis, University of Auckland, 2009. http://hdl.handle.net/2292/3377.
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Aims: To determine the effect of induced myopia on the in vivo scleral biomechanical properties and scleral cell populations in the guinea pig. Methods: One week old guinea pigs were monocularly deprived of form vision (MD) for 14 days. Cycloplegic refractive error was measured with an IR Optometer, and the results analysed using power vectors and linear mixed modelling. The in vivo ocular biomechanical response was investigated by raising the IOP to 50 mmHg for one hour in anaesthetised animals. A-scan ultrasound measures of axial length were taken every 10 minutes with raised IOP, and after returning IOP to 15 mmHg. The total cell population (DAPI antibody) and myofibroblast population (α-SMA antibody) was determined in transverse scleral sections from the posterior 100 degrees of each eye. Results: The average relative myopic refractive error induced was -4.06 ± 0.35 D, which was mainly the result of vitreous chamber depth (VCD) elongation. This was confirmed by a negative correlation between mean sphere and VCD (R2 = 0.4295). On increasing the IOP the deprived and control eyes showed rapid viscoelastic expansion of the VCD that normal eyes did not show. When the increased IOP was maintained the deprived and control eyes showed lower creep rates than normal eyes. Myofibroblasts were shown to be present in guinea pig sclera, as previously observed in human and tree shrew sclera. On average, approximately 64% of the scleral cells were myofibroblasts. The induction of myopia had minimal effect on the cell populations, except for a decrease in total cell numbers in the 10° region equivalent to the location of scleral crescent formation in myopic human eyes. Conclusions: Ahigh proportion of scleral cells show contractile potential in the guinea pig. Form deprivation appears to minimally affect cell numbers, except in the region equivalent to scleral crescent formation in myopic human eyes. However, the in vivo viscoelastic response of the VCD in deprived eyes differs from that in normal eyes, suggesting some factor(s) other than cell number alone has a role in axial length control.
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McMahon, George. "The genetics and epidemiology of myopia in the ALSPAC cohort." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54159/.
Full textAbstract:
An aim of this thesis is to map a genetic factor that is related to myopia progression. A genome-wide association study of myopia, refractive error and two ocular determinants of refractive error, axial length and corneal curvature was undertaken. A number of genetic locations were identified and extra genotyping and replication in an independent cohort is underway. A further aim of this thesis is investigation of an environmental risk factor of myopia. Epidemiological analyses of two myopia risk factors were undertaken; one in the ALSPAC cohort, another in a cohort from Northern England. In both cases, a relationship with myopia was identified and a plausible mechanism for the relationship is discussed.