Thesis (M.S.)--New England College of Optometry, 2008. / Includes bibliographical references (p. 51-57).

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xv, 144 p.; also includes graphics (some col.) Includes bibliographical references (p. 129-144). Available online via OhioLINK's ETD Center

Age, sex, race, heredity, environment and nutrition have been found to influence ametropia. In this study, the distribution of refractive errors has been investigated in relation to age, sex, race, education and near work, and lighting conditions. Visual awareness and vision screening in pre-school and schoolchildren were also investigated. Data were collected using the Nikon auto-refractor, retinoscope, Snellen V.A chart, and subjective techniques. 777 people were refracted, whose ages ranged between four and eighty years. Measurements were made in different sections of Umlazi township, therefore people of different socio-economic sectors were refracted. Four year-old children were found to be hyperopic. Hyperopia decreased and refraction shifted towards emmetropia. Myopia started to appear at the age of ten. Myopia increased until the age of twenty, and thereafter decreased slowly until the age of thirty three, where the average refraction was emmetropia. From age forty onwards, hyperopia was predominant. The incidence of high astigmatism, high hyperopia and high myopia is low in this community. Most people fall in the spherical refractive error region of between -1.000 and +1.000. The curve is leptokurtotic with highest peak around +0.250. The cylindrical error is between -0.500 and -1.000. No significant difference between sexes was found except at the fourth age group (40-51), where females are more hyperopic than males. The other sex difference is at ages ten to twelve, where females develop myopia earlier than males. Illumination plays no important role in the development of refractive errors in this community. Education and near work seem to account very little to the development of myopia. The influence of heredity on the development of ametropia was not investigated in depth. However, there is no evidence of heredity influencing the development of ametropia. There is a lack of vision screening and visual awareness. / Thesis (M.Optom.)-University of Durban-Westville, 1988.

Purpose: WHO reports 46% of world vision impairment from refractive error (RE) among children occurs in China. We estimated RE prevalence and associated vision impairment (VI) among Chinese children and adults. Methods: Data from population-based studies were stratified by gender in age intervals of 3 years (ages 3-17 y) or 10 years (ages >= 30 y): counts of persons with myopia (worse eye spherical equivalent <= -1.0D, <= -2.0D, <= -6.0D) and prevalence of low vision (< 6/12 in the better-seeing eye for children and < 6/18 for adults) and blindness (<=6/60) attributable to RE. Figures for VI included persons with habitual vision below the cutoff improving to above the cutoff with refraction, and those with myopic retinopathy. Estimates for ages 18-29 y were obtained from regression models derived from the pooled estimates. Prevalence of myopia and VI attributable to RE in each age/gender category was calculated by applying modeled rates to 2000 China census figures and projections for 2020. Association with VI attributable to RE was tested for: gender, urban versus rural residence, and residence in provinces with per capita GDP in the upper versus lower 50% for China. Results: Data were obtained from 5 cohorts for children and 14 for adults. There were 291 million and 21.4 million persons with myopia <= -1.0D and <= -6.0D respectively in 2000, expected to rise to 306 million and 36.9 million by 2020. Of these, 18.4 million were blind and 116 million had low vision in 2000, with figures of 25.3 million and 123 million in 2020. Children accounted for the following proportion of RE disease burden in China in 2000: myopia <= -1.0D: 19.0%; RE-associated low vision: 56.1%; blindness: 14.1%. Refractive error was responsible for 82.3% of blindness and 90.5% of low vision among children, and 11.6% and 64.4% of blindness and low vision among adults. Urban residence (OR 1.85, P = 0.004) and higher GDP (OR 10.6, P < 0.001) were associated with refractive blindness among children. For adults, lower GDP was associated with refractive blindness (OR 1.47, P = 0.01). Gender was un-associated with refractive blindness among children or adults. Conclusions: Both children and adults suffer a heavy burden of VI associated with RE in China. Income may affect risk for such VI differently among children and adults. / published_or_final_version / Public Health / Master / Master of Public Health

M.Phil. (Optometry) / Please refer to full text to view abstract

Este trabalho tem como finalidade o desenvolvimento de um sistema objetivo e automático de medidas de vícios de refração ocular. Para tanto, a forte interação entre a Física e a Oftalmologia foi de fundamental importância para que o objetivo fosse atingido. Foram desenvolvidos quatro sistemas, dentre os quais, três são completamente distintos entre si no que se refere aos princípios utilizados para a determinação das ametropias oculares, bem como no que se refere ao modo de detecção da luz retro-espalhada pela retina. O quarto sistema é apenas um refinamento do terceiro que se apresentou eficaz para o uso clínico. O terceiro e quarto sistemas, denominados Sistemas DVL-1 e DVL-2, têm como base a projeção com um laser de diodo de um alvo luminoso no fundo do olho do paciente. Os feixes emergentes do olho testado são divididos em seis partes (três meridianos) e são analisados dois a dois por um CCD (linear no caso do sistema DVL-1 e matricial no caso do sistema DVL-2). A distância entre as duas imagens formadas em cada meridiano fornece o poder de refração naquele meridiano. Com os poderes de refração dos três meridianos (0&#176, 120&#176 e 240&#176) é possível determinar o erro refrativo ocular. Testes em réplicas oculares apresentaram uma precisão média de 0,06di (a precisão aceitável para este tipo de exame oftalmológico é de 0,125di) e em olhos in vivo 0,125di para as coordenadas esférica e cilíndrica e 5&#176 para o eixo de astigmatismo, o que está dentro das precisões clínicas necessárias. / The purpose of the present work is the development of an objective and automatic system for ocular refractive errors measurements. Hence, a strong interaction between Physics and Ophthalmology was fundamentally important in order to provide the success of the work four systems have been developed, where three of them are completely different from each other in the sense of the basic principles used for determining the ocular ametropies, as well as for the detection of the scattered light from the retina. System four is just an improvement of system three, which has presented a good efficiency for clinical use purposes. The third and fourth systems, called DVL-1 and DVL-2 systems, consist on projecting a target in the fundus of the tested eye with a diod laser light. The beams which emerge from the tested eye are divided into six portions (three meridians) and are analyzed in pairs by a CCD (linear CCD for DVL-1 and matrix CCD for DVL-2). The distances between the two images in each meridian provide the refractive power in that particular meridian. As the refractive power is obtained for the three meridians (0&#176, 120&#176 e 240&#176), it is possible to determine the ocular refractive error . Tests in artificial eyes have been done and an average error of 0,06di was obtained (0,125di is the allowed precision for this kind of examination). For measurements in vivo eyes a precision of 0,125di for spherical and cylindrical coordinates were obtained, as well as a 5&#176 precision for the axis of astigmatism. These precision values are the ones required by the clinical evaluation.

Este trabalho tem como finalidade o desenvolvimento de um sistema objetivo e automático de medidas de vícios de refração ocular. Para tanto, a forte interação entre a Física e a Oftalmologia foi de fundamental importância para que o objetivo fosse atingido. Foram desenvolvidos quatro sistemas, dentre os quais, três são completamente distintos entre si no que se refere aos princípios utilizados para a determinação das ametropias oculares, bem como no que se refere ao modo de detecção da luz retro-espalhada pela retina. O quarto sistema é apenas um refinamento do terceiro que se apresentou eficaz para o uso clínico. O terceiro e quarto sistemas, denominados Sistemas DVL-1 e DVL-2, têm como base a projeção com um laser de diodo de um alvo luminoso no fundo do olho do paciente. Os feixes emergentes do olho testado são divididos em seis partes (três meridianos) e são analisados dois a dois por um CCD (linear no caso do sistema DVL-1 e matricial no caso do sistema DVL-2). A distância entre as duas imagens formadas em cada meridiano fornece o poder de refração naquele meridiano. Com os poderes de refração dos três meridianos (0&#176, 120&#176 e 240&#176) é possível determinar o erro refrativo ocular. Testes em réplicas oculares apresentaram uma precisão média de 0,06di (a precisão aceitável para este tipo de exame oftalmológico é de 0,125di) e em olhos in vivo 0,125di para as coordenadas esférica e cilíndrica e 5&#176 para o eixo de astigmatismo, o que está dentro das precisões clínicas necessárias. / The purpose of the present work is the development of an objective and automatic system for ocular refractive errors measurements. Hence, a strong interaction between Physics and Ophthalmology was fundamentally important in order to provide the success of the work four systems have been developed, where three of them are completely different from each other in the sense of the basic principles used for determining the ocular ametropies, as well as for the detection of the scattered light from the retina. System four is just an improvement of system three, which has presented a good efficiency for clinical use purposes. The third and fourth systems, called DVL-1 and DVL-2 systems, consist on projecting a target in the fundus of the tested eye with a diod laser light. The beams which emerge from the tested eye are divided into six portions (three meridians) and are analyzed in pairs by a CCD (linear CCD for DVL-1 and matrix CCD for DVL-2). The distances between the two images in each meridian provide the refractive power in that particular meridian. As the refractive power is obtained for the three meridians (0&#176, 120&#176 e 240&#176), it is possible to determine the ocular refractive error . Tests in artificial eyes have been done and an average error of 0,06di was obtained (0,125di is the allowed precision for this kind of examination). For measurements in vivo eyes a precision of 0,125di for spherical and cylindrical coordinates were obtained, as well as a 5&#176 precision for the axis of astigmatism. These precision values are the ones required by the clinical evaluation.

M.Phil. / Cataracts have been identified as one of the leading causes of blindness, especially in the developing world. The only presently known effective treatment for this growing problem is surgical removal of the opaque lens followed by replacement with an artificial intra ocular lens. Newer methods have brought greater success, and greater costs. For people in the developing world, these newer methods are not always an option. Together with the increased cost, there is a growing demand because of this worldwide problem. This increased need for surgery has lead to the development of waiting lists in the state funded hospitals. To qualify for a cataract extraction in most state funded hospitals, a best visual acuity of 6/60 is required, compared to the 6/12 to 6/24 levels required in the industrial countries and private practices. With these levels of visual impairment in the developing world, many patients are left functionally blind for long periods of time until cataract extraction can be performed. Older methods such as extra-capsular cataract extraction are still being used in the developing world. This is mostly due to the increased density of the cataracts at the time when the extraction can be performed because of the long waiting time leading to further maturation of the cataract. This method requires a large corneal incision, which is normally closed with nylon sutures. With this method of surgery meticulous wound closure is very important, and in many cases surgically induced astigmatism is one of the unwanted consequences. It was therefore decided, for the purpose of this study, to use autokeratometric data to explore the refractive effects of two different methods of corneal wound closure following planned extra-capsular cataract extraction (ECCE). Astigmatism is a major problem associated with extra capsular cataract extraction, especially when the wound is closed by means of sutures. Studies by Minassian et al. (2001), Jacobi (2003) and Dowler et al. (2000) all show that newer methods of cataract extraction making use of smaller incisions and therefore fewer sutures show faster recovery and less astigmatism. These methods are however mostly restricted to private practice, and therefore potentially unsuited for use in developing countries. The type of material used for wound closure is another very important factor. Depending on the method of suturing wound gape and wound compression can cause increased amounts of astigmatism. Using a method of wound closure that would cause less traction on the cornea could therefore cause less of a problem postoperatively. Tissue adhesives such as Tisseel® fibrin glue could be such an alternative. Studies by Henrick et al. (1987), Kim and Kharod (2007) and Bhatia (2006) show that fibrin glue forms a watertight, non irritating wound while promoting the healing process by the cross linking of collagen fibres.

Orientador: Silvana Artioli Schellini / Banca: Milton Ruiz Alves / Banca: Carlos Eduardo Leite Arieta / Banca: Maria Rosa Bet de Moraes Silva / Banca: Flávio Eduardo Hirai / Resumo: Determinar o perfil de distribuição dos erros refracionais em uma amostra populacional do centro-oeste do Estado de São Paulo, suas possíveis associações com características individuais e a influência sobre a acuidade visual. foi desenvolvido estudo de secção transversal com amostragem residencial probabilística e sistemática em nove municípios no sul do centro-oeste paulista, como parte do Projeto de Prevenção à Cegueira na Comunidade. Os indivíduos acima de um ano de idade foram submetidos a entrevista e exame oftalmológico completo. A acuidade visual em sistema Snellen e posterior conversão para logMAR foi obtida antes e após exame de refração e categorizada em quatro segmentos. Os erros refracionais foram classificados em miopia (EE ≤ - 0,50D), hipermetropia (EE ≥ 0,50D), astigmatismo (DC ≤ -0,50D) e anisometropia (diferença de EE ≥ 1,00D entre os olhos). Foi realizada a análise descritiva dos dados de prevalência na amostra, análise univariada e multivariada com modelos de regressão logística múltipla para determinar possíveis associações de prevalências. 3012 residências foram entrevistadas e 7654 indivíduos foram incluídos no estudo, sendo 62,7% mulheres, 92,1% considerados com pele branca e média para a idade de 36,89 anos (extremos de 1 a 96 anos). A miopia foi mais prevalente na terceira e quarta décadas de vida, atingindo 43,31% sem diferenças significativas entre sexos, enquanto a hipermetropia foi mais prevalente entre mulheres acima de 60 anos de idade, com uma frequência de 65,6% nesta faixa etária. O astigmatismo apresentou uma frequência progressivamente maior com a idade e semelhante entre os sexos. O eixo do astigmatismo também apresentou variação conforme a idade, com o eixo horizontal mais frequente em jovens e o vertical nos idosos. A prevalência da anisometropia apresentou variação com a idade sendo mais frequente nos extremos de idade, ... / Abstract: Establish the refractive errors distribution in a population sample of the Central São Paulo State, correlations with personal features and its influence in visual acuity. A cross sectional survey was developed with randomized and systematic residential sampling in nine cities of middle region of São Paulo St/Brazil as part of Blindness Prevention Project at Community. Inhabitants above one year old were submitted to an interview and full ophthalmic exam. Visual acuity in logMAR system was determined before and after refraction exam and classified in four categories. Refractive errors were classified in myopia (SE ≤ -0,50D), hyperopia (SE ≥ 0,50D), astigmatism (CD ≤ -0,50D) and anisometrophy (SE difference between eyes ≥ 1,00D). Prevalence data sample were submitted to descriptive analysis, univariate and multivariate logistic regression models to find eventual prevalence associations. 7654 participants were included in this survey, in which 62,7% were women, 92,1% with white skin and middle age of 36,89 years old (1 to 96 years). Myopia was more prevalent at 3rd and 4th decades, achieving 43,31% without significant differences between genders, while hyperopia was more prevalent in women above 60 years old, with 65,5%. Astigmatism prevalence increased by age with no differences between genders. Astigmatism axis changed by age too, when horizontal axis were more frequently observed in youngers and vertical in olders. Anisometrophy prevalence changed by age, more frequent at extremes, achieving 32,66% after 70 years old. No significant differences were found in ethnic categories. Visual acuity increasing prevalence by visual impairment corrected with spectacles (UREN) was 6,53% in the total sample, mainly after 60 years old and high refrective errors. Prevalence associations were found between age and all ametrophic categories, sex and hyperopia and between UREN with myopia, hyperopia and ... / Doutor

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&lt0.001). 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 &lt 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 (&gt -10.00 D) can be over 1.00 D.