Thesis (M.S.)--Ohio State University, 2009. / Title from first page of PDF file. Includes vita. Includes bibliographical references (p. 57-59).

Thesis (MPH.) --University of Limpopo, 2015 / Background: Uncorrected refractive errors remain a public health problem among different population and age groups worldwide, including South Africa. Refractive error has serious visual and functional impacts on those affected. In children, refractive errors may negatively affect the academic pursuits and activities of daily living such as reading. Aims and Objectives: To determine and document the prevalence, types and magnitude together with age and gender differences of refractive errors among primary school children in Motherwell Township, Eastern Cape Province, South Africa. Methods: This was a quantitative, cross sectional refractive error study. Four hundred and twenty one (421) school children aged 7 – 14 years were randomly selected from five randomly selected schools in Motherwell Township, Eastern Cape Province, South Africa. Visual examination which included unaided and aided visual acuity (with LogMAR E chart), non-cycloplegic autorefraction, subjective refraction, internal and external examination of the eye using an ophthalmoscope was conducted. Refractive errors were measured with an autorefractor, refined subjectively and findings presented in spherical form. Hyperopia was defined as a spherical equivalent (SE) of +0.50 D or greater, myopia as spherical equivalent of -0.50 D or greater. A cylindrical power of -0.50 DC (D cylinder) or greater was considered as astigmatism. Results: The prevalence of hyperopia, myopia and astigmatism among the children were 25.2%, 18.7% and 58.0% respectively. Hyperopia ranged from +0.50 to +3.62 D and myopia ranged from -0.50 D to -20.25 D in the right eyes with a mean of -0.17 ± 1.7 D. In the left eye, hyperopia ranged from +0.50 to +2.62 D and myopia ranged from -0.50 to -20.62 D with a mean of -0.12 ± 1.7 D. Astigmatism in the right eyes ranged from -0.50 to -5.50 D with a mean of -0.6 ± 0.52 D and in the left eye ranged from -0.50 to -4.00 D with a mean of -0.6 ± 0.45 D respectively. Association between hyperopia and age was not statistically significant (p = 0.839), also refractive error and gender was statistically insignificant (p = 0.120). Against-the-rule (ATRA) astigmatism (43.4%) was more common, followed by with-the-rule (WTRA) astigmatism (39.0%) and oblique, (all other meridians) (17.6%). There was a significant association between types of astigmatism and age (p = 0.05), more so inter-gender difference in the prevalence of different types of astigmatism was not statistically significant (p = 0.774). Conclusion: The study concludes that refractive error has high prevalence of 43.9% in this children population. Astigmatism (58.0%) was more common followed by hyperopia (25.2%) v and myopia (18.7%). Although hyperopia was not age dependent, there was obvious relationship pattern between female genders and hyperopia in the present study. Population-based vision screening or at least school visual screening in the rural communities of Motherwell Township is, therefore recommended. Vision screening and proper eye examination with appropriate optical compensation will improve the activity of daily living and quality of life of those affected. Key words: Refractive error, hyperopia, myopia, astigmatism, school children

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BACKGROUND: Laser vision correction (LVC) developed as a more permanent alternative to other forms of refractive error correction. In the last several decades, visual outcomes of corneal refractive surgeries like LVC have improved dramatically with the discovery of new technologies and techniques designed to make the patient experience more comfortable and worthwhile. LVC has been shown to safely and effectively treat refractive errors in myopic and hyperopic eyes, with gradually improving outcomes and safety measures. However, it is important to note whether specific excimer lasers impart the same level of safe, effective treatments for patients as technology advances. OBJECTIVE: This study aims to identify whether any statistically significant difference exists in the visual and refractive outcomes of hyperopic laser vision correction using two excimer laser platforms, the VISX STAR S4 IR® and the WaveLight® EX500, and to determine whether either laser shows any statistically significant difference in the rate of repeat surgery within one year post-operatively. METHODS: Using EMR data collected from December 2008 through December 2016, distance and near visual acuity outcomes for hyperopic eyes treated with LASIK, LASEK, or PRK were compared at one month and up to one year post-operatively. Distance eyes were compared separately from monovision (near-targeted) eyes for visual acuity; however, if manifest refraction post-operative data were available, they were used to identify whether any difference existed in the refractive outcomes in either category. The number of enhancements (repeat surgeries) was also tabulated. X2 Tests of Independence were used to determine statistical significance. RESULTS: Visual acuity outcomes in distance eyes at one month post-operatively showed similar trends between the two lasers, with 54% of the 267 VISX- and 60% of the 119 EX500-treated eyes presenting with UCVA of 20/20 or better. Eyes available for follow-up within one year post-operatively kept with this trend; 98 (51%) VISX- and 58 (67%) EX500-treated, eyes had UCVA measured at 20/20 or better. For monovision (treated for reading vision) eyes, 29 (47%) eyes and 19 (54%) of VISX- and EX500-treated eyes, respectively, read J1+ by one month post-operatively. By one year, 16 (39%) and 3 (21%) of available eyes read J1+ after treatment with the VISX and EX500 respectively. The relative enhancement rate was 7.82% (28 eyes) on the VISX and 4.19% (7 eyes) on the EX 500. CONCLUSION: Overall, visual outcomes of laser vision correction for hyperopic patients did not differ consistently between the two lasers. Only distance-treated eyes measured up to one year post-operatively showed a statistically significant difference between the two lasers. The visual and, more importantly, the refractive outcomes were statistically similar at both one month and up to one year post-operatively irrespective of treatment type. Enhancement rate between the two lasers also showed no differences. Both lasers are similarly safe and effective for treating hyperopia and hyperopic astigmatism. / 2018-01-11T00:00:00Z

OBJETIVO: Avaliar a eficácia, estabilidade, previsibilidade e segurança da ceratectomia fotorrefrativa (PRK) guiada pelas frentes de onda corneana para o tratamento da hipermetropia secundária à ceratotomia radial (CR). MÉTODOS: Foram avaliados prospectivamente 61 olhos de 39 pacientes consecutivos, submetidos a PRK personalizado com o laser Esiris-Schwind. A técnica constou de desepitelização mecânica, fotoablação, e utilização de mitomicina C (MMC) 0,02% por 20 ou 40 segundos. A MMC foi aplicada por 40 segundos em 17 olhos (27,9%) que haviam sido submetidos a ablações mais profundas do que 100 ?m ou apresentavam córneas previamente suturadas. As avaliações pós-operatórias foram realizadas após sete dias, um, seis, 12 e 24 meses. Todos os olhos foram avaliados após um ano e dois anos. RESULTADOS: O intervalo médio entre a CR e o PRK foi de 18,8 anos ± 3,8 (DP); o equivalente esférico (EE) médio antes da ceratotomia radial era -4,10 dioptrias (D) ± 1,44. As medidas prévias ao PRK mostraram EE médio de +4,17 D ± 1,97; astigmatismo médio de -1,39 D ± 1,04; AV com correção (AVcc) média de 0,161 ± 0,137 (logMAR); e curvatura corneana média de 35,85 ± 3,60 D. Os resultados encontrados dois anos após a cirurgia foram: EE médio de 0,14 ± 0,99 D (p < 0,001); astigmatismo médio de -1,19 ± 1,02 D (p = 0,627); AV sem correção (AVsc) média de 0,265 ± 0,196 (p < 0,001); AVcc média de 0,072 ± 0,094 (p < 0,001); e curvatura corneana média de 39,01 ± 3,18 D (p < 0,001). AVsc igual ou melhor a 20/25 foi observada em 38% dos olhos e igual ou melhor a 20/40 em 69%. A AVcc melhorou em 62,3% dos olhos, sendo que 21 olhos (34,4%) melhoraram uma linha e outros 17 olhos (27,9%), duas ou mais linhas. Um olho (1,6%) perdeu duas linhas devido ao astigmatismo irregular ocasionado por opacificação corneana periférica. Outro olho perdeu três linhas pelo desenvolvimento de ectasia corneana entre seis e 24 meses, devido ao alargamento progressivo de uma incisão radial inferior, e foi posteriormente submetido à sutura da incisão. Houve 30 olhos (49,2%) entre ± 0,50 D do EE planejado e 45 (73,8%) entre ± 1,00 D. Entre seis e 24 meses, a regressão média do EE foi de +0,39 D (p < 0,05) e cinco olhos (8,3%) sofreram desvio hipermetrópico > 1,00 D. Ocorreu redução estatisticamente significante do coma (p = 0,001), trefoil (p = 0,008), aberração esférica (p < 0,001), astigmatismo secundário (p = 0,001) e quatrefoil (p < 0,001). Não houve mudança estatisticamente significativa da contagem endotelial (p = 0,161). Dois olhos (3,3%) desenvolveram opacificação corneana periférica grau 2 e um, grau 3. CONCLUSÃO: O PRK personalizado pelas frentes de onda corneana coadjuvado pela MMC foi eficaz, previsível e seguro pelo período de dois anos para a redução da hipermetropia após a CR. No pós-operatório observou-se melhora significativa da AVsc, AVcc e das aberrações corneanas. Constatou-se, entretanto, que a hipermetropia consecutiva à CR continua a progredir após o tratamento com o excimer laser. / PURPOSE: To assess the efficacy, stability, predictability and safety of corneal wavefront-guided photorefractive keratectomy (PRK) for correcting hyperopia after radial keratotomy (RK). METHODS: In a prospective study, 61 eyes of 39 consecutive patients were treated with PRK using an Esiris-Schwind excimer laser. Corneal epithelium was mechanically removed, followed by photoablation and use of 0.02% mitomycin C (MMC) for 20 or 40 seconds. MMC was used for 40 seconds in 18 eyes (27.9%) which underwent ablations deeper than 100 micron or had previous corneal sutures. Postoperative evaluations were performed after seven days, six, 12 and 24 months. All patients were followed up for two years. RESULTS: The mean time between RK and PRK was 18.8 years ± 3.8 (SD); mean spherical equivalent (SE) before RK was -4.10 diopters (D) ± 1.44. Before PRK, the mean SE was +4.17 D ± 1.97, mean astigmatism was -1.39 D ± 1.04, the mean best-corrected visual acuity (BCVA) was 0.161 ± 0.137 (logMAR) and the mean corneal curvature was 35.85 ± 3.60 D. At 24 months, mean SE was 0.14 ± 0.99 D (p < 0.001), mean astigmatism was -1.19 ± 1.02 D (p = 0.627), mean UCVA was 0.265 ± 0.196 (p < 0.001), mean BSCVA was 0.072 ± 0.094 (p < 0.001) and the mean corneal curvature was 39.01 ± 3.18 D (p < 0.001). UCVA was 20/25 or better in 38% of eyes and 20/40 or better in 69%. BCVA improved in 62.3% of eyes, with 21 (34.4%) gaining one line and 17 (27.9%), two or more lines. One eye (1.6%) lost two lines due to irregular astigmatism and peripheral haze. Another eye lost three lines due to keratectasia occurring between six and 24 months resulting from widening of an inferior radial incision that was later sutured. Thirty eyes (49.2%) were within ± 0.50 D of intended SE and 45 (73.8%) were within ± 1.00 D. From six to 24 months, the mean SE regression was +0.39 D (p < 0.05) and five eyes (8.3%) had a hyperopic shift > 1.00 D. A significant decrease in coma (p = 0.001), trefoil (p = 0.008), spherical aberration (p < 0.001), secondary astigmatism (p = 0.001) and quatrefoil (p < 0.001) was observed. Endothelial cell counts did not show a statistically significant decrease (p = 0.161). Two eyes (3.3%) developed peripheral haze grade 2 and one, grade 3. CONCLUSION: Corneal wavefront-guided PRK with MMC was effective, predictable and safe after two years for the treatment of hyperopia after RK. A significant improvement in UCVA, BSCVA and corneal aberrations was obtained. However, hyperopic shift after RK continued to progress after excimer laser surgery.

Objetivo: Estudar os componentes refrativos da hipermetropia em crianças com ambliopia por esotropia, comparando os olhos amblíopes com os olhos contralaterais. Métodos: Foram incluídos 37 pacientes de 5 a 8 anos de idade, com hipermetropia bilateral e ambliopia por esotropia. Foi realizada avaliação oftalmológica completa, incluindo refratometria sob cicloplegia, ceratometria e biometria ultrassonográfica modo A. Foram registrados profundidade da câmara anterior, espessura do cristalino, profundidade da câmara vítrea e comprimento axial total. O poder refrativo do cristalino foi calculado pelas equações de Bennett. Para comparar erro refrativo, poder da córnea, poder calculado do cristalino e componentes ecobiométricos entre os olhos amblíopes e os olhos contralaterais foi empregado o teste t de Student pareado. Para avaliar a relação entre os principais componentes refrativos individuais e o erro refrativo foram empregados o coeficiente de correlação de Pearson e a análise de regressão linear. Foram construídos também modelos multivariados, incluindo comprimento axial, poder da córnea e poder do cristalino. Resultados: Os olhos amblíopes apresentaram hipermetropia mais alta, menor poder da córnea, maior poder do cristalino, menor profundidade da câmara vítrea e menor comprimento axial. Não houve diferença entre os olhos quanto à profundidade da câmara anterior ou à espessura do cristalino. A variável que apresentou correlação mais forte com o erro refrativo foi a razão comprimento axial/raio de curvatura da córnea (r = -0.92, p < 0.001 nos olhos amblíopes e r = - 0.87, p < 0.001 nos olhos contralaterais). O comprimento axial representou 39,2% da explicação da variabilidade do erro refrativo nos olhos amblíopes e 35,5% nos olhos contralaterais. O modelo que combinou comprimento axial e poder da córnea explicou 85,7% e 79,6% da variabilidade do erro refrativo, respectivamente. Houve correlação significante entre comprimento axial e poder da córnea, indicando diminuição do poder da córnea com o aumento do comprimento axial e os coeficientes de correlação foram semelhantes entre os olhos amblíopes (r = -0.53, p <0.001) e os olhos contralaterais (r = -0.57, p < 0.001). Houve correlação significante entre comprimento axial e poder do cristalino, indicando diminuição do poder do cristalino com o aumento do comprimento axial e os coeficientes de correlação também foram semelhantes entre os olhos amblíopes (r = -0.72, p < 0.001) e os olhos contralaterais (r = -0.69, p < 0.001). Conclusão: As correlações entre os principais componentes refrativos e sua contribuição individual para o erro refrativo foram semelhantes nos olhos amblíopes e nos olhos contralaterais de crianças com esotropia, a despeito da hipermetropia mais alta nos olhos amblíopes / Purpose: To study the refractive components of hyperopia in children with esotropic amblyopia, comparing amblyopic eyes with fellow eyes. Methods: Thirty-seven patients (5 to 8 years old) with bilateral hyperopia and esotropic amblyopia underwent a comprehensive ophthalmic examination, including cycloplegic refraction, keratometry and A-scan ultrasonography. Anterior chamber depth, lens thickness, vitreous chamber depth and total axial length were recorded. The refractive power of the crystalline lens was calculated using Bennett`s equations. Paired Students t-tests were used to compare refractive error, corneal power, calculated lens power and ocular biometric measurements between amblyopic eyes and their fellow eyes. The relationship between the major oculometric parameters and refractive error was assessed using Pearson correlation coefficients and linear regression. Multivariable models including axial length, corneal power and lens power were also constructed. Results: Amblyopic eyes were found to have significantly more hyperopic refraction, lesser corneal power, greater lens power, shorter vitreous chamber depth and shorter axial length, despite similar anterior chamber depth and lens thickness. The strongest correlation with refractive error was observed for the axial length/corneal radius ratio (r = -0.92, p < 0.001 for amblyopic and r = -0.87, p < 0.001 for fellow eyes). Axial length accounted for 39.2% of the refractive error variance in amblyopic eyes and 35.5% in fellow eyes. The combination of axial length and corneal power accounted for 85.7% and 79.6% of the refractive error variance respectively. A significant correlation was found between axial length and corneal power, indicating decreasing corneal power with increasing axial length, and they were similar for amblyopic eyes (r = -0.53, p < 0.001) and fellow eyes (r = -0.57, p < 0.001). A significant correlation was found between axial length and lens power, indicating decreasing lens power with increasing axial length, and they were also similar for amblyopic eyes (r = -0.72, p < 0.001) and fellow eyes (r = -0.69, p < 0.001). Conclusion: The correlations among the major refractive components and their individual contribution to refractive error were similar in amblyopic and non-amblyopic eyes in esotropic children, despite more hyperopic refraction in amblyopic eyes

This thesis makes a contribution to that part of the economics literature that explores how behavioural economics can inform environmental economics. Theoretically, the thesis develops the concept of environmental morale. Empirically, the study investigates the role of environmental morale on individuals’ behaviour within two different contexts: recycling participation and intertemporal choices over different goods (i.e., money, environment, and health) and outcomes (i.e., gains and losses). Major objectives of this analysis are: to shed light on how environmental morale interplays with individuals’ behaviour under different recycling policy schemes, and to examine whether temporal discounting is domain specific and depends on environmental morale heterogeneity. Original survey investigations are employed to analyse these issues. Results highlight the relevance of environmental morale both in motivating individuals’ contribution to recycling and intertemporal choices towards environmental outcomes. Regarding the interaction between environmental morale, recycling participation and government interventions, results from this analysis suggest that a facilitating nudge policy seems to be relatively more powerful in increasing individuals’ contribution and motivation towards recycling. Considering intertemporal choices, a paradox of hyperopia seems to be located in data provided in this analysis. Some of the original contributions of the thesis are, first the broader reconceptualization of the definition of environmental morale and its operationalization in analyses of questionnaire preferences. Secondly, in line with other areas of research (i.e., tax compliance literature); this study pursues an investigation of individual and cultural differences with respect to recycling policies, an area which has been neglected in the environmental economics literature. In this regard, the analysis considers a comparison between psychology and economics students in Italy and the UK. Thirdly, conditioning discounting on environmental morale offers a unique opportunity to analyse how ethical considerations influence the way individuals form expectations on (near and far distant) future environmental outcomes.

Thesis (M. Optometry) -- University of Limpopo, 2019 / BACKGROUND The measurement of the refractive end point plays a major role in the assessment of the refractive status of the patient. Currently, there are very few techniques if not one that can measure the refractive end point of the patient. The current method which is the duochrome technique is based on chromatic aberration. Until now there is no test for refractive end point that is not based on chromatic aberration. Therefore, it was against this background that the current study was undertaken to investigate an alternative for the duochrome technique to measure the refractive end point. AIM OF THE STUDY The aim of this study was to establish the use of cross grid in conjunction with Jackson crossed cylinders at distance as a monocular refractive end point technique. METHODOLOGY A cross-sectional analytic and descriptive study design was used. Sixty-four subjects (31 males and 33 females) were included in this study. Their ages ranged from 18 to 37 years with a mean of 20.75 years (SD = ± 2.67 years). The participants were University of Limpopo Optometry students. Ethical approval to perform this study was obtained from the Turfloop Research Ethics Committee (TREC) of University of Limpopo. All participants were made aware of the purpose of the study, and signed consent was obtained from each participant. All investigations and measurements adhered to the tenets or principles, belief and requirements of the Declaration of Helsinki. Optometric procedures performed included visual acuity, subjective measurement of refractive error, monocular refractive end point using duochrome technique and monocular refractive end point measurement using gross grid in conjunction with the cross grid. Data analysis was done using the Statistical Package for Social Sciences (SPSS) Version 23. Paired sample t-test was performed on all the procedures. RESULTS The uncorrected distance VA for the right eyes (OD) ranged from -0.30 LogMAR to 1.00 LogMAR with a mean of -0.25 LogMAR (SD = ±0.32). The nearest equivalent spherical powers (NSE = sphere +0.5 cylinder) for the right eye ranged from -4.25 to +4.25D (mean = -0.13, SD= ±1.09D) and from -4.50D to +1.00D (mean = +0.07 ±0.94D) for the left eye. After the removal of outliers, the refractive end point measurements with the duochrome technique for the right eyes ranged from -4.50D to 3.50D with a mean of -0.269, SD (±1.037) in bright illumination and from -4.50D to 4.50D with a mean of -1.914 (±1.101) in dim illumination. Subsequently, the NSE with the crossed cylinder in conjunction with the cross grid technique for the right eyes in bright illumination ranged from -4.75D to 4.75D with a mean of -0.481, SD (±1.037) and from -4.25D to 0.50D with a mean of -0.427 (±0.860) in dim illumination. Sample Pearson correlation coefficients for end point with duochrome and crossed cylinder found that the highest correlation is between the duochrome in bright and cross grid in dim illumination (r = 0.701, p < 0.05), while duochrome in dim and cross grid in bright illumination had the lowest correlation (r = 0.659). The Bland–Altman plots showed that there was a good agreement between the duochrome methods and between the crossed cylinder method methods. CONCLUSION the refractive end point measurements obtained from duochrome and cross grid are well correlated and comparable, suggesting that they could be used interchangeably in most clinical settings. However, caution is needed when using measurements obtained by cross grid method in dim illumination.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.