Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 110-119). Also available via the Internet.

Thesis (M. Sc.) -- Lincoln University, 2006.

Undergraduate honors paper--Mount Holyoke College, 2007. Program in Biochemistry. / Includes bibliographical references (leaves 64-67).

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nÃo hà / Com a cirurgia de catarata moderna realizada em cÃrneas normais, independente da tÃcnica cirÃrgica utilizada, hà uma perda celular endotelial mÃdia de 10 a 20%. SubstÃncias viscoelÃsticas foram desenvolvidas com a funÃÃo de manter os espaÃos naturais do olho e conferir proteÃÃo mecÃnica Ãs estruturas intraoculares durante a cirurgia. O objetivo deste estudo foi realizar uma anÃlise comparativa do efeito de duas formulaÃÃes viscoelÃsticas, metilcelulose a 2% e 4%, na proteÃÃo do endotÃlio corneano contra o dano secundÃrio à facoemulsificaÃÃo. Foi realizado um estudo prospectivo, randomizado e duplo cego com pacientes portadores de catarata senil, submetidos à cirurgia de facoemulsificaÃÃo com Implante de Lente Intraocular (LIO). Todos os pacientes foram submetidos a uma avaliaÃÃo oftalmolÃgica completa, incluindo microscopia especular. ApÃs o exame inicial, os pacientes foram randomizados em dois grupos: no grupo A (n=63) foi utilizada a metilcelulose 2% e no grupo B (n=63) a metilcelulose 4%. A mÃdia da Densidade de CÃlulas Endoteliais (DCE) mostrou-se significativamente reduzida (p<0,05), tanto na anÃlise intra como na intergrupo no 1Â, 15 e 30 dias de pÃs-operatÃrio, representando uma perda de cÃlulas endoteliais de 15,26% e 6,79% nos grupos A e B, respectivamente. A Espessura Central da CÃrnea (ECC) mostrou-se aumentada no 1 dia pÃs operatÃrio (DPO) no grupo A, sendo este dado estatisticamente significante (p<0,05). Houve aumento no Coeficiente de VariaÃÃo da tamanho celular (CV) e diminuiÃÃo no Percentual de CÃlulas Hexagonais (6 A), no entanto, sem significÃncia estatÃstica para esses dois parÃmetros. ConcluÃmos que, à despeito das vantagens da metilcelulose a 4% em relaÃÃo à diminuiÃÃo de perdas de cÃlulas endoteliais apÃs facoemulsificaÃÃo, ambos os viscoelÃsticos sÃo semelhantes em relaÃÃo a parÃmetros clÃnicos como ECC, CV e 6A, os quais refletem a manutenÃÃo de condiÃÃes fisiologicamente adequadas para o bom funcionamento do endotÃlio. No entanto, devido à pequena diferenÃa de custo entre os dois produtos e os benefÃcios da metilcelulose 4%, esta pode ser considerada um produto de escolha em cirurgias de catarata de rotina, uma vez que as indicaÃÃes de facoemulsificaÃÃo estÃo sendo cada vez mais precoces, devido Ãs exigÃncias visuais dos pacientes, promovendo, desta forma, cÃrneas mais saudÃveis por longo prazo. / Modern cataract surgery in normal corneas, independent of the surgical technique used, causes a mean 10 to 20% loss of endothelial cells. Viscoelastic substances were developed with the function of maintaining the natural spaces of the eye and providing mechanical protection to the intraocular structures during surgery. The objective of this study was to perform a comparative analysis of the effect of two viscoelastic compositions, methylcellulose 2% and 4%, in corneal endothelial protection against secondary damage to the phacoemulsification procedure. We performed a prospective, randomized, double-blind study with senile cataract patients, submitted to phacoemulsification surgery with intraocular lens (IOL) implant. All patients were submitted to a complete ophthalmological assessment, including specular microscopy. After initial assessment, the patients were randomized into two groups: in Group A (n=63) we used methylcellulose 2%, and in Group B (n=63) methylcellulose 4%. There was no statistically significant difference for the parameters analyzed between groups before surgery. However, at 30 days after surgery, mean density of endothelial cells (DCE) was 2128.78Â277.55 cells/mm in Group A and 2395.79Â262.16 cells/mm in Group B, representing a 15.15 and 6.76% loss of endothelial cells in Groups A and B, respectively. Mean DCE was significantly reduced (p<0.05), in both the inter- and inter-group analysis on the 1st, 15th, and 30th day after surgery. ECC increased on the 1st day after surgery in group A, this datum was statistically significant (p<0.05). There was no statistical difference for the other parameters assessed. In this study, we conclude that, despite the advantages of methylcellulose 4% over 2% in regards to the reduction of endothelial cell loss after phacoemulsification, both viscoelastic substances are similar in relation to clinical parameters such as central corneal thickness, coefficient of variation in cell size and percentage of hexagonal cells, which reflect corneal preservation and maintain adequate physiological conditions for proper endothelial function. However, due to the slight difference in cost between the two products and the benefits of methylcellulose 4% on endothelial cell preservation, this may be considered a choice product in routine cataract surgery, as indications for phacoemulsification are increasingly early, due to patientsâ visual demands, promoting, in this manner, healthier corneas in the long term.

Cataract surgery is one of the most common procedures performed in the entire world. Cataracts are inevitable in anyone who live to old age and as the global population continues to age, the number of cataract surgeries that are expected to be performed each year is only expected to increase. The procedure is also one of the oldest and has matured a substantial amount since its first utilization but it is still not perfect. It is crucial that we continue to improve to procedure in pursuit of improved post-operative outcomes for patients. In this study, a delayed phacoemulsification after the femtosecond laser anterior capsulotomy and lens fragmentation was introduced into the procedure with the hypothesis that this may allow the cataract to hydrate and soften, leading to an intraoperative reduced phacoemulsification power and a post-operative preservation of the corneal endothelium in grade 4 nuclear cataracts. This study is a new study with very little data collected so far but it is planned that we will initially perform the procedure on 10 patients with bilateral grade 4 cataracts. Each patient will have the new procedure done on one eye and then the typical cataract surgery procedure done on the other eye to be used as a statistical comparator. This thesis specifically explores the concept of introducing a delay between the capsulotomy and the phacoemulsification process and the safety and feasibility of such procedure in practice. The new procedure, so far, has been performed on one patient with the surgery data for the other eye currently pending. Relevant data such as cumulative dissipated energy and intraocular pressures were recorded during and after the surgery for future comparisons. Without a complete set of data, a statistical conclusion cannot be made about the efficacy of the new procedure, but as addressed in this thesis, the procedure has been concluded to be safe and feasible with a good post-operative outcome.

published_or_final_version / Molecular Biology / Doctoral / Doctor of Philosophy

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