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Abstract(s)
Introdução: Têm surgido no mercado diversos tipos de LIO multifocais que têm como função restaurar a visão de perto através de pseudoacomodação. No processo de controlo de qualidade deste tipo de LIO é necessário avaliar diversos parâmetros de qualidade de imagem, nomeadamente as medidas de distâncias focais, de resolução e da Função de Transferência de Modulação ao longo de várias vergências (Through-focus MTF). A técnica de transporte de intensidade é um método que emprega uma montagem ótica para gerar uma sequência de mapas de intensidade luminosa transmitida pelo objeto em análise. A informação sobre a frente de onda proveniente do objeto é digitalizada e reconstruída por meio de métodos de processamento de imagem. Uma vez que a informação sobre a amplitude e a fase da frente de onda são preservadas, é possível reconstruir a Função de Transferência Ótica de uma lente para diversas distâncias com base em apenas dois registos bidimensionais de intensidade ótica.
Objetivo: O objetivo principal deste estudo consiste na adaptação da técnica baseada na equação de transporte de intensidade à avaliação da qualidade ótica de lentes intraoculares, através da simulação computacional e desenvolvimento prático de um protótipo laboratorial especialmente desenhado para o efeito.
Métodos: Este trabalho experimental envolve três fases principais: A primeira envolve a realização de simulações no programa de traçado de raios Oslo® e em ambiente de programação MATLAB® para prever o desempenho da técnica de transporte de intensidade na reconstrução de frente-de-onda e cálculo de métricas de qualidade de imagem. A segunda fase diz respeito ao desenvolvimento da montagem ótica com base num laser He-Ne (632 nm) e numa configuração 4f. Esta montagem é testada numa terceira fase, utilizando duas lentes de contacto (de +8,00D e de +10,5D) e uma lente intraocular monofocal (+26.50D).
Resultados: De acordo com as simulações, tanto a potência da lente como o nível de ruído têm impacto na escolha do parâmetro de desfocagem ???, devendo o seu valor situar-se os 150 e os 200 ??m. A técnica mostra uma boa robustez ao ruído, mas revela fragilidades em lentes de potências elevadas. Os dados experimentais permitiram recuperar o defocus (??4) associado à lente de +10,50D com um erro de cc de 24%. Contudo, os valores das aberrações não foram corretamente recuperados. A montagem adaptada à lente intraocular de +26.50D revelou extrema sensibilidade a erros de alinhamento.
Conclusões: O forte efeito de curvatura da frente de onda devido ao defocus (??4) deverá ser removido para que as aberrações de ordem superior e outras métricas de qualidade de imagem possam ser recuperadas, sobretudo para potências superiores a +10,00D. A técnica poderá ser mais facilmente adaptada a lentes de contacto de baixa potência do que lentes intraoculares.
Introduction: Several types of multifocal IOLs that have the function of restoring close vision through pseudoacomodation have appeared on the market. In the process of quality control of this type of IOL it is necessary to evaluate several parameters of image quality, namely the focal length, resolution and the Modulation Transfer Function through various distances (Through-focus MTF). The intensity transport technique is a method that employs an optical assembly to generate a sequence of light intensity maps transmitted by the subject under analysis. Information about the wavefront from the object is digitized and reconstructed by means of image processing methods. Once the wavefront amplitude and phase information is preserved, it is possible to reconstruct the Optical Transfer Function of a lens for various distances based on only two two-dimensional registers of optical intensity. Objective: The main objective of this study is the adaptation of the technique based on the intensity transport equation to the evaluation of the optical quality of intraocular lenses, through the computational simulation and practical development of a specially designed laboratory prototype. Methods: This experimental work involves three main phases: The first one involves simulations in the Oslo® ray tracing program and in the MATLAB® programming environment to predict the performance of the intensity transport technique in wavefront reconstruction and computation of image quality metrics. The second phase concerns the development of the optical assembly based on a He-Ne laser (632 nm) and a 4f configuration. This assembly is tested in a third phase, using two contact lenses (+ 8.00D and + 10.5D) and a monofocal intraocular lens (+ 26.50D). Results: According to the simulations, both the lens power and the noise level have an impact on the choice of the ? desf blur parameter, and its value should be 150 and 200 µm. The technique shows good robustness to the noise, but reveals weaknesses in lenses of high powers. The experimental data allowed to recover the defocus (??4) associated to the lens of + 10,50D with a dc error of 16%. However, the aberration values were not correctly recovered. The fitting adapted to the intraocular lens of + 26.50D revealed extreme sensitivity to alignment errors. Conclusions: The strong wavefront curvature effect due to defocus (??4) should be removed so that higher order aberrations and other image quality metrics can be recovered, especially for powers greater than + 10.00D. The technique may be more easily adapted to low-power contact lenses than intraocular lenses.
Introduction: Several types of multifocal IOLs that have the function of restoring close vision through pseudoacomodation have appeared on the market. In the process of quality control of this type of IOL it is necessary to evaluate several parameters of image quality, namely the focal length, resolution and the Modulation Transfer Function through various distances (Through-focus MTF). The intensity transport technique is a method that employs an optical assembly to generate a sequence of light intensity maps transmitted by the subject under analysis. Information about the wavefront from the object is digitized and reconstructed by means of image processing methods. Once the wavefront amplitude and phase information is preserved, it is possible to reconstruct the Optical Transfer Function of a lens for various distances based on only two two-dimensional registers of optical intensity. Objective: The main objective of this study is the adaptation of the technique based on the intensity transport equation to the evaluation of the optical quality of intraocular lenses, through the computational simulation and practical development of a specially designed laboratory prototype. Methods: This experimental work involves three main phases: The first one involves simulations in the Oslo® ray tracing program and in the MATLAB® programming environment to predict the performance of the intensity transport technique in wavefront reconstruction and computation of image quality metrics. The second phase concerns the development of the optical assembly based on a He-Ne laser (632 nm) and a 4f configuration. This assembly is tested in a third phase, using two contact lenses (+ 8.00D and + 10.5D) and a monofocal intraocular lens (+ 26.50D). Results: According to the simulations, both the lens power and the noise level have an impact on the choice of the ? desf blur parameter, and its value should be 150 and 200 µm. The technique shows good robustness to the noise, but reveals weaknesses in lenses of high powers. The experimental data allowed to recover the defocus (??4) associated to the lens of + 10,50D with a dc error of 16%. However, the aberration values were not correctly recovered. The fitting adapted to the intraocular lens of + 26.50D revealed extreme sensitivity to alignment errors. Conclusions: The strong wavefront curvature effect due to defocus (??4) should be removed so that higher order aberrations and other image quality metrics can be recovered, especially for powers greater than + 10.00D. The technique may be more easily adapted to low-power contact lenses than intraocular lenses.
Description
Keywords
Equação de Transporte de Intensidade Lentes Intraoculares Qualidade de Imagem