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Home    Ανάπτυξη αισθητήρα μετώπου κύματος hartmann-shack για τον ανθρώπινο οφθαλμό και σύγκριση του με εμπορικά διαθέσιμους αισθητήρες  

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Identifier 000379193
Title Ανάπτυξη αισθητήρα μετώπου κύματος hartmann-shack για τον ανθρώπινο οφθαλμό και σύγκριση του με εμπορικά διαθέσιμους αισθητήρες
Alternative Title The development of a Hartmamm-shack wavefront sensor for the human eye and comparison with the availablecommercial wavefront sensors.
Author Τιμοθεάτος, Σ Σταύρος
Thesis advisor Τσιλιμπάρης, Μιλτιάδης
Reviewer Δετοράκης, Ευστάθιος
Παλλήκαρης, Ιωάννης
Abstract The aim of this thesis was to develop an experimental set-up of a Shack-Ηartmann wavefront sensor for measuring aberrations of human eyes and compare it with WASCA(wavefront aberration supported cornea ablation, Carl Zeiss Meditec) based in Shack-Ηartmann technique and i-trace (, Tracey Techology) based on a the principle of laser ray tracing technique. A historical recursion for the invention and use of Shack-Ηartmann wavefront analyzer is discussed in the introduction, and the Hartmann technique of the screen test. Reference is made for Shack-Ηartmann use from astronomy to ophthalmology. At the first chapter the general anatomy of the eye is reported, more specifically the cornea, the crystalline lens, the retina, the optic nerve and the superior optical signal processing, as well as the visual and refractive eye function of the eye. Subsequently the factors affecting the quality of the image of the retinal image is reported. The performance of the eye’s optical media that affect the quality of the image on the retina is the normal functioning of the retina and the superior image processing of the image in the cortex. Visual factors that determine the sharpness of the image is originally the diffraction and the pupil size, the ocular monochromatic and chromatic aberrations, high and low order, the adaptive ability of the eye and the scattering phenomenon. The neural factors are the density of photoreceptors in the fovea, the functionality of the photoreceptors and optical signal processing in the optical and superior neuronal pathway. Finally psychological factors are also important. The second chapter refers to the principles of abberometry. The basic principle of wavefront analyzers is presented for the science of vision, which is based on: an indirect measurement of local slope (𝜵𝜽), and the rebuilding of the total wavefront by mathematical integration of the slope. It also refers to the sensors for wavefront aberrations measurements of the eye and its operating principles, such as the spatial refractometer, the Tscherning method, the Laser Ray Tracing method and the Shack-Hartmann method. Additionally the parameters that have to be taken into account in the design of a Shack-Hartmann sensor are presented. Details on the way that operation of wavefront reconstruction occur, using Zernike coefficients is also presented. The third chapter is the experimental part of the master thesis. The following experiments were made: a) alignment and calibration of the experimental setup of the Shack-Hartmann system, b) measurements of the intensity of the brightness of the system source and the reliability of the algorithm for calculating Zernike coefficients c) artificial eye measurements for reliable device operation, and measurements in eleven normal eyes for 5 mm pupil and eight normal eyes for 6 mm pupil. The experimental results were compared with two commercial aberrometers, the WASCA and i-Trace. This chapter reports the results of measurements for the brightness of the source and from the calibration experiment of the system with the use of the Badal base. The iv differences from comparing the results of simulation algorithm were investigated and a statistical comparison of results of Zernike coefficients with paired t-test was made. The results from the comparison of our experimental procedure to theoretical defocus in artificial eye were presented. Finally, Zernike coefficients and the RMS of human eyes were determined and compared for each of the three machines, or a 5.6 mm pupil. Defocus, cylinder and sphere was also determined. Statistical comparison was made with paired t-test for both Zernike coefficients and RMS. In conclusions the proper functioning of the experimental set-up and the reliability operation of the algorithm for calculating Zernike coefficients was determined. In the experiment of the artificial eye, a linear correlation and similar variation of theoretical calculation of the defocus and calculations with the use of the device was exhibed. Comparison of this study’s experimental data with the Wasca and i-Trace, showed that measurements of the system are closer to those of Wasca, and any differences were mainly due the lack of automation detection of the pupil of the experimental set yp as compared to the commercial systems.
Language Greek
Subject Aberrations of the eye
Aberrometry
Hartmann-shack
I-Trace
Ophthalmology
Optical set up
Wasca
Wavefront reconstruction
Wavefront sensor
Zernike polynomias
Αισθητήρας μετώπου κύματος
Ανακατασκεή μετώπου κύματος
Εκτροπές οφθαλμού
Οπτική διάταξη
Πολυώνυμα Zernike
Issue date 2013-04-16
Collection   School/Department--School of Medicine--Department of Medicine--Post-graduate theses
  Type of Work--Post-graduate theses
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