The impact of uncoordinated growth of the optical components of the eye may stimulate different levels of monochromatic aberrations in the growing eyes of the children. This thesis aimed to examine the impact of age, visual acuity and refractive error on higher order aberrations as well as to determine the relationship between them. Hartman Shack images taken with the Welch Allyn® SureSight Autorefractor were calibrated in order to determine the Zernike coefficients up to the 8th order for a pupil diameter of 5mm. The MATLAB code proposed by Thibos et al that follows the standard for reporting the optical aberrations of the eye was the basis of code written for this study. Modification was required to suit the specific needs of the Welch Allyn® SureSight Autorefractor. After calibration the lower order aberrations could then be compared with the results from cyclopledged retinoscopy. RMS values of aberrations and Strehl ratios were computed to examine the optical performance of the eye. A total of 834 Hartmann-Shack images of 436 children (mean age 3.94± 0.94 years, range 3 to 6 years) were examined in this study (right eyes 436; left eyes 398).The sample had a mean (± STD) spherical equivalent of 1.19 ± 0.59D, a mean with-the-rule astigmatism (J0) of 0.055 ± 0.22D, and a mean oblique astigmatism (J45) of 0.01±0.14D. Visual acuity varied from 6/6 to 6/18. Moderate mirror symmetry was found between the eyes. Like refractive error, higher order aberrations declined with age in this sample. There was an impact of higher order aberrations on refractive error. Significantly higher ocular aberrations were found in the higher hyperopic group (SE>+2.0D) compared to emmetropic (-0.5<SE<+0.5D) and low hyperopic groups (+0.5<SE<+2.0D). The Strehl ratio was significantly lower in the high hyperopic group. Higher Strehl ratios were observed for better acuity groups but the average Strehl ratios among the different visual acuity groups were not statistically significant. In conclusion, there was an impact of age on the ocular aberrations. A wider range of age from birth to adolescence is required for further investigation. This could be indirectly influenced by the age related changes in refractive error as the correlation between refractive error and the higher order aberrations were significant. This finding also concludes that Strehl Ratio alone is not capable of perfectly describing the visual acuity of the eye; other metrics such as the neural transfer function and neural noise are necessary to describe the resultant visual performance of the eye.

Thèse de doctorat : Sciences de la vie et de la santé : Paris 12 : 2005. / Version électronique uniquement consultable au sein de l'Université Paris 12 (Intranet). Titre provenant de la version imprimée. Pagination : 110 f. Bibliogr. : 134 réf.

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Classical field curvature theory emphasizes the Petzval theorem, which models field curvature aberration to the 4th order. However, modern lens designs use aspheric surfaces. These surfaces strongly induce higher order field curvature aberration which is not accounted for Petzval field curvature. This dissertation focuses on developing higher order field curvature theories that are applied to highly aspheric designs. Three new theories to control field curvature aberration are discussed. Theory 1: an aspheric surface that is close to the image and has two aspheric terms sharply reduces field curvature by 85%. Theory 2: an aspheric surface that is farther from the image plane induces astigmatism to balance Petzval field curvature. Theory 3: oblique spherical aberration can be induced to balance Petzval field curvature. All three theories are applied to real design examples including the following lenses: cellular phone, wide angle, fast photographic, and zoom lenses. All of the analyses results are consistent with the theories. Moreover, two types of novel aspheric surfaces are proposed to control field curvature. Neither of the surfaces are polynomial-type surfaces. Examples show that the novel aspheric surfaces are equivalent to even aspheric surfaces with two aspheric coefficients in terms of field curvature correction. The study on field curvature correction using aspheric surfaces provides an alternative method to use when aspheres are accessible. Overall, this dissertation advances the theory of field curvature aberration, and it is particularly valuable to evaluate highly aspheric designs when Petzval theory is inapplicable.

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It is known that a phase-perturbed object field from a fractal-like rough surface illuminated by a partially coherent beam generates speckle on the image plane. In this works, aberration effects on Gaussian speckle on the image plane in both perfectly and partially coherent systems are theoretically and experimentally investigated. Theory shows that the second order statistics of Gaussian laser speckle are independent of odd-functional aberrations, but they do affect Gaussian speckle contrast in a partially coherent system. Furthermore, it is theoretically derived that field statistics of Gaussian laser speckle generally become non-circular Gaussian due to aberrations, and an aberration effect is asymptotically ignorable for very weak or strong roughness. A brute force simulation method is introduced for non-Gaussian speckle in a partially coherent imaging system, where speckle irradiance is calculated from a quasi-monochromatic extended incoherent source. The source is modeled as a collection of independent point sources distributed on a regular grid. The partially coherent speckle pattern is calculated from the incoherent sum of coherent speckle patterns in the image plane generated from each point source. Speckle contrasts from a brute force model show good agreement with theoretical and experimental results. It is determined that non-Gaussian speckle contrast is strongly dependent on Hurst exponent of fractal rough surfaces using brute force simulations. The concept of a contributing object area at a fixed image point effectively explains the speckle contrast dependency. Measuring spherical aberrations using Gaussian laser speckle is discussed as one of applications and future works of the present study.

Thesis (Ph. D.)--University of Canterbury, 2002. / Typescript (photocopy). "March 2002." Includes bibliographical references (p. 191-197). Also available via the World Wide Web.

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