Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

Although there is considerable published research on the efficacy and corneal response to orthokeratology (OK) lenses that flatten corneal curvature to correct myopia, the effects of OK lenses that attempt to steepen corneal curvature to correct hyperopia are poorly understood. This project investigated the effects of hyperopic OK lens wear on corneal shape, refraction and vision. Open-eye and closed-eye overnight studies were conducted with proprietary hyperopic OK lenses, and these led to the development of an experimental hyperopic OK lens design which allowed manipulation of individual lens design parameters. Changes to refraction and best corrected visual acuity (BCVA), corneal topography (Medmont E300), and the profile of total and stromal corneal thickness (Holden-Payor optical pachometer) were measured over periods up to one week of overnight lens wear. Most refractive change occurred after the first night of wear, with increasing effect towards one week. Retention of effect at the end of the day increased with more nights of lens wear. BCVA decreased with longer periods of lens wear. Greater inter-subject variability in effect was found with higher refractive targets. The central cornea steepened and para-central cornea flattened producing a central steepening zone (CSZ) surrounded by a para-central annular flattened zone. CSZ diameter reduced with longer periods of lens wear, and this was significantly associated with decreases in high and low contrast BCVA. There was no change in central corneal thickness beyond the normal overnight lens induced hypoxic edema response. Once edema had resolved thinning of the para-central corneal epithelium was found which resulted in an overall thinning of the para-central cornea. Although central lens fenestrations did not affect the hyperopic OK response, a stronger relationship between changes to apical corneal curvature and refraction resulted. This supports the conclusion that the hyperopic OK effect is due to molding of the corneal surface towards alignment with the lens back surface. Similarities to the pattern of clinical change in myopic OK suggest that a similar corneal molding mechanism occurs in myopic OK. BCVA loss prevented longer term studies and needs to be resolved if hyperopic OK is to become established as a viable clinical technique.

Diss. (sammanfattning) Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.

Thesis (M.S.)--New England College of Optometry, 2009. / Includes bibliographical references (p. 94-96).

Dissertation (Ph.D.)--University of South Florida, 2006. / Includes vita. Includes bibliographical references (leaves 156-180). Also available online.

Thesis (M.Med.Sc.)--University of Hong Kong, 2002. / Includes bibliographical references (46-49). Also available in print.

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Made available in DSpace on 2014-06-11T19:31:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-07-17Bitstream added on 2014-06-13T18:41:51Z : No. of bitstreams: 1 sampaio_rl_dr_botfmvz.pdf: 2038576 bytes, checksum: 0813f5677fc511ad064fc7bf63955284 (MD5) / Universidade Estadual Paulista (UNESP) / O presente estudo foi empreendido com o objetivo de estabelecer a cinética da resposta inflamatória e conhecer os mecanismos envolvidos na reparação de córneas tratadas por ceratoplastia utilizando, como método experimental, o emprego de membrana amniótica xenógena a fresco e conservada em glicerina no recobrimento de úlceras experimentais. Para o desenvolvimento da metodologia proposta utilizou-se 70 coelhos, os quais foram distribuídos em 5 grupos experimentais. Os animais foram avaliados por 21 dias, período durante o qual observou-se fenômenos relacionados à resposta inflamatória local, como dor, edema de córnea e conjuntiva, hiperemia conjuntival, além dos fenômenos relacionados à reparação da córnea, como a infiltração vascular e epitelização da úlcera experimentalmente criada. Para tanto, os olhos foram avaliados através de exame clínico oftalmológico, estudo histopatológico e reação imunohistoquímica, através da qual pesquisou-se a presença de linfócitos T na intimidade do tecido corneano. A avaliação clínica revelou que a membrana amniótica xenógena conservada em glicerina estimulou uma resposta inflamatória aguda maior que a membrana aplicada a fresco. A análise histopatológica indicou que ambas se comportaram de forma bastante semelhante a partir da 1a semana de pós-operatório, apresentando as alterações clássicas da resposta inflamatória da córnea, com o predomínio de infiltrado do tipo polimorfonuclear. Os fenômenos de reparação também evoluíram respeitando os padrões normais para ambos os tratamentos, tendo sido observado, porém, que a epitelização do defeito foi mais rápida nas córneas que receberam o enxerto de membrana a fresco. A aplicação da técnica de imunohistoquímica indicou que em nenhum momento de observação houve a migração de linfócitos T para o... (Resumo completo, clicar acesso eletrônico abaixo).

Orientador: José Luiz Laus / Banca: Duvaldo Eurides / Banca: Márcia Rita Fernandes Machado / Resumo: São diversas as indicações para o emprego de adesivos derivados do cianoacrilato na área médica. Em oftalmologia humana, há décadas, estes biomateriais são utilizados com resultados satisfatórios. Entretanto, em veterinária, ainda são escassos o conhecimento de suas propriedades e a sua aplicação. Considerando o interesse em se avaliar o comportamento do etil-cianoacrilato, comparativamente ao octil-cianoacrilato, clínica e histopatologicamente, em córneas de coelhos, empregaramse 36 animais, nos quais, após ceratectomia lemelar de 3 mm de diâmetro, os adesivos foram aplicados e recobertos por uma fina película acelular. No pós-operatório, foram realizadas avaliações gerais (dias 1 a 10), exames oftálmicos (dias 0, 1, 3, 5, 7, 10, 14, 21, 30, 44 e 60) e estudos histopatológicos (períodos 3, 7, 14, 21, 30 e 60). Consideraram-se, ainda, os custos e disponibilidade dos adesivos. Clinicamente, houve diferença significativa para as variáveis, consumo de água, atitude, blefarite, edema corneal, teste da fluoresceína e tempo de permanência dos adesivos. À histopatologia, para o etil-cianoacrilato, já nos primeiros períodos de avaliação, observou-se epitelização corneal, organização do colágeno e moderada reação inflamatória. Para o octil-cianoacrilato, constatou-se a permanência do adesivo até as fases mais tardias, sob o qual, mais lentamente os eventos de reepitelização e organização do colágeno ocorreram com reação inflamatória discreta. Os custos e disponibilidade de aquisição do etil-cianoacrilato foram mais acessíveis do que os do octil-cianoacrilato. / Abstract: There are several indications for the employment of adhesives derived from the cyanoacrylate in the medical area. In human ophthalmology, from decades, the cyanoacrylates have been used with satisfactory results. However, in veterinary medicine, there is a scarcity of knowledge of its properties and applications. Considering the objective of evaluating the behavior of the ethyl-cyanoacrylate, comparatively to octhyl-cyanoacrylate, clinically and histopatologically, in rabbit corneas, there were used 36 animals. After lamellar keratectomy with 3 mm of diameter the adhesives was applied and recovered with a fine pellicle. In the post operative period general (days 1 to 10), ophthalmic (days 0, 1, 3, 5, 7, 14, 21, 30, 44 and 60) and hystopathologic (periods 3, 7, 14, 21, 30 and 60) exams was performed. There was also considered the costs and accessibility of the adhesives. Clinically, there were significant differences for the variables water consumption, attitude, blepharitis, corneal edema, fluorescein test and adhesive permanence time. With respect to the histopathological evaluation, for the treatment with ethyl-cyanoacrylate, there was observed already in the very first periods of evaluation, corneal epitelization, collagen organization and moderate inflammatory reaction. For the octhyl-cyanoacrylate treatment, there was observed the adhesive permanence until later phases, under which more vagarously the events of reepithelization and collagen organization occurred with a discrete inflammatory reaction. The ethyl-cyanoacrylate presented minor costs and more facility to acquire. / Mestre