Alfredo Dubra's PhD thesis - Imperial College London

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Abstract The evaluation of the optical quality of the human eye beyond spectacle prescription has recently become a very active field, given the number and importance of applications that can benefit from it: refractive surgery, retinal imaging, monitoring of intraocular lens performance, psychophysical experiments and adaptive optics spectacles for improving visual acuity and increasing accommodation range in presbyopic subjects. Several ophthalmic wavefront sensors have been recently developed to measure the imaging properties of the eye, most of them based on the use of a Shack-Hartmann configuration. Despite the current widespread use of wavefront sensing based refractive surgery, there are a number of related issues not yet well understood, one of the most important being the variability of the wavefront sensor measurements due to eye movements, heart beat, fluctuations of accommodation and tear film dynamics. The work in this thesis focuses on the study of tear film dynamics and its effects on the optical quality of the eye. In order to do so, a lateral shearing interferometer to measure the pre-corneal tear film topography was designed, built and used to study 20 subjects. The collected data was processed with a novel reconstruction technique, which is applicable to any lateral shearing interferometry experiment, and the results are discussed in terms of the tear film influence of the optical quality of the eye, which can be used to understand the effects on vision, wavefront sensing and adaptive optics. Finally, the feasibility of using interferometry to evaluate the wavefront error of the eye by modifying the lateral shearing interferometer was also tested. 1
Acknowledgements Pursuing the PhD degree at Imperial has been a life changing experience both inside and outside the lab, and for this, I have to thank a few people. To begin with, thanks Paula for your support in the mad idea of coming to London to start a PhD with no funding. I then have to say that I am greatly indebted to my supervisor Chris Dainty for getting this funding (and Luis Diaz-Santana) and providing the academic freedom and confidence in the project. I am also grateful to Chris for the work environment he created both in the Applied Optics groups at Imperial and NUI Galway. Much of the research undertaken for this thesis was the result of several discussions with Carl Paterson, even before he was my supervisor. The experiments performed during the PhD were only possible thanks to the patience of and quality of work from, the guys in the mechanical and optics workshop: Paul Brown, Martin Kehoe, Simon Johnson and Martin Dowman. Thanks to all the people that volunteered to put their eyes in front of a laser beam and have their mouths stuck in a wax block for nothing in return. That is true generosity. It is said that one should not mix business with pleasure, but the most valuable thing I will take from my PhD is the friends I made at work; thanks to Fred Reavell for his immense patience with my poor engineering skills, the explanation of English culture and motorcycle tuition. Being in a lab with no windows and having to deal with the same project for three years (and a series of unsuccessful experiments) could have driven me insane, had it not been for the company of David Lara, Steve Gruppetta, Jonathan Brooks, Karen Hampson, Gordon Kennedy, James McIlroy, Ian Munro, David Catlin, Simon Clay and Allison Craig. There have been some seriously hard times on a personal level during the PhD, which I only came through with the company and support from Mo and Si. Thanks to them I came closer to the true English culture (and slang), sometimes difficult to find in such a cosmopolitan place and more importantly, I found two friends for life. There was a time when working long hours in front of the computer and a lonely lab made me lose all perspective of life. Fortunately, Chris Dainty took me to Galway for 2
Page 1: A Shearing Interferometer for the E
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Bibliography [1] T. Young. The Bake
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BIBLIOGRAPHY [22] P. Artal, S. Marc
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BIBLIOGRAPHY [44] Austin Roorda and
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BIBLIOGRAPHY [67] W.N. Charman and
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BIBLIOGRAPHY [89] J.P. Craig, P.A.
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BIBLIOGRAPHY [115] Frangois C. Delo
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Alfredo Dubra's PhD thesis - Imperial College London

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