Navegando por Palavras-chave "Optometria"

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    Análise comparativa entre a refração clínica subjetiva e a automatizada obtida por sensor de frentes de onda
    (Conselho Brasileiro de Oftalmologia, 2007-08-01) Freitas, Wilson de [UNIFESP]; Melo Júnior, Luiz Alberto Soares [UNIFESP]; Schor, Paulo [UNIFESP]; Campos, Mauro Silveira de Queiroz [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    PURPOSE: To evaluate and compare refractive errors obtained through clinical subjective and automatized wavefront refraction analyses in eyes under cycloplegia. METHODS: Prospective study of 147 patients, 279 eyes, undergoing preoperative examination for refractive surgery. Clinical subjective refraction was performed first followed by wavefront refraction. Results on astigmatism obtained from refraction were decomposed in power vectors for statistical analyses. Data were first analyzed in one eye and then in both eyes. RESULTS: The mean difference between clinical subjective refraction and automatized wavefront refraction on cycloplegic eyes was of -0.19 SD combined with -0.06 CD in the 15º axis for data in one eye, and -0.17 SD combined with -0.05 CD in the 3º axis for data in both eyes of the same patient. CONCLUSION: In the present study clinical subjective refraction and automatized wavefront refraction under cycloplegia had similar numerical values.
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    Analise comparativa entre a refracao clinica subjetiva e a automatizada obtida por um sensor de frentes de onda
    (Universidade Federal de São Paulo (UNIFESP), 2004) Freitas, Wilson [UNIFESP]
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    Interchangeability between Placido disc and Scheimpflug system: quantitative and qualitative analysis
    (Conselho Brasileiro de Oftalmologia, 2010-08-01) Stefano, Vinícius Silbiger de [UNIFESP]; Melo Junior, Luiz Alberto Soares [UNIFESP]; Mallmann, Felipe [UNIFESP]; Schor, Paulo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    PURPOSE: Many systems try to replace Placido disc-based topographers, such as those based in Scheimpflug principles. The purpose of this study is to check if they are interchangeable. METHODS: Quantitative analysis evaluated data obtained from EyeSys and Pentacam, i.e. simulated keratometric values, in addition to flattest and steepest keratometric values. Sixty-three maps from each device (EyeSys scale=0.5 D; Pentacam scale= 0.25 D) were used for the comparison. Qualitative analysis selected 10 EyeSys and 15 Pentacam topographies used in the quantitative evaluation. Aspheric, keratoconus suspects (KS) and established keratoconus corneas were included. Four groups (children [CH], non-physicians adults [AD], residents in ophthalmology [OP] and refractive surgeons [RS]) were asked to match the topographies belonging to the same eye. RESULTS: Analysis showed that the parameters are correlated; however they are not clinically similar. In the qualitative analysis, the percent of correct matches increased when KS was removed. CH group was statistically different from every group in these comparisons. When only KS was considered, CH vs. OP, CH vs. RS and AD vs. RS remained statistically different. AD vs. OP showed no relevant difference in any comparison. CONCLUSIONS: The systems are not fully interchangeable, yet they are correlated. Practitioners who are adapting to Pentacam should use the 0.25 D scale maps and transform formulas that use EyeSys parameters. Only with persistent training may the topographies be properly matched; KS corneas are more difficult to be correctly paired.
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    Preliminary results of a high-resolution refractometer using the Hartmann-Shack wave-front sensor: part I
    (Conselho Brasileiro de Oftalmologia, 2003-06-01) Carvalho, Luis Alberto; Romao, Antonio Carlos; Stefani, Marcos; Carvalho, Luiz Antonio; Castro, Jarbas Caiado De; Yasuoka, Fátima; Scannavino Júnior, Francisco; Santos, Juselino Dos; Schor, Paulo [UNIFESP]; Chamon, Wallace [UNIFESP]; Eyetec Equipamentos Oftálmicos Ltda; Universidade Estadual de Maringá; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    In this project we are developing an instrument for measuring the wave-front aberrations of the human eye using the Hartmann-Shack sensor. A laser source is directed towards the eye and its diffuse reflection at the retina generates an approximately spherical wave-front inside the eye. This wave-front travels through the different components of the eye (vitreous humor, lens, aqueous humor, and cornea) and then leaves the eye carrying information about the aberrations caused by these components. Outside the eye there is an optical system composed of an array of microlenses and a CCD camera. The wave-front hits the microlens array and forms a pattern of spots at the CCD plane. Image processing algorithms detect the center of mass of each spot and this information is used to calculate the exact wave-front surface using least squares approximation by Zernike polynomials. We describe here the details of the first phase of this project, i. e., the construction of the first generation of prototype instruments and preliminary results for an artificial eye calibrated with different ametropias, i. e., myopia, hyperopia and astigmatism.