PHYSIOLOGIC OPTICS

Author: FERNÁNDEZ MUÑOZ JUAN ALVARO.
Year: 2003.
University: EXTREMADURA [www.unex.es].
Place of defense: ESCUELA DE INGENIERIAS INDUSTRIALES.
Place of preparation: ESCUELA DE INGENIERIAS INDUSTRIALES.

Summary: In this thesis defines specific neural structures for the realization of image processing. They adapt algorithms classical image processing to the neural structures by increasing the performance of the process using multilayer structures and the adoptive setting the parameters of the neural output functions. It has been defined and the same neuronal structure that is capable of performing transform Focurier, from Hartley, in two dimensions, thereby facilitating the conduct of a neural processing in the frequency domain.

Author: CAMPS SANCHIS VICENT JESÚS.
Year: 2004.
University: VALENCIA [www.uv.es].
Place of defense: facultad de fisica.
Place of preparation: FACULTAD DE FISICA.

Author: CASTEJÓN MOCHÓN JOSÉ FCO.
Year: 2005.
University: MURCIA [www.um.es].
Place of defense: FACULTAD DE QUÍMICA.
Place of preparation: FACULTAD DE QUÍMICA.

Summary: Aberration wave eye is closely linked to the visual quality and characteristic values presented in each eye. Its measurement and correction have a great interest both in the field of basic science as in clinical practice. In this paper we develop an experimental system of measurement of wavefront eye with a large dynamic range based on a sensor Shack-Hartmann. It will measure the ocular aberrations monochrome into two groups of subjects: one of young people with healthy eyes and other subjects that have undergone corneal transplant (queratoplastia penetrating). The results show that the RMS value midst of the high order aberrations is 10 times higher in the latter. In addition there was a high correlation between the corneal aberrations (obtained from the corneal topography) and the aberrations of the eye corneal pathology group. It explores, in a simulated and real, the correction of aberrations through hydrophilic contact lenses, designed from the pattern of aberrations in each subject. The study was carried out for three types of eyes: normal, with queratoconos and cornea transplant. The results show that the major limitations of this type of correction arise because of the position and orientation average of the contact lens in the eye. If we take into account realistic displacement of the contact lens found that normal subjects show a loss of optical quality over standard correction (correction esfero-cilíndrica). However, there are pathological cases where despite the usual rotations and translations of contact lenses, we could reduce the RMS for aberrations and enhance the visual quality, as verified experimentally in queratoconos.

Author: DIAZ DOUTON FERNANDO.
Year: 2005.
University: POLITÉCNICA DE CATALUÑA [www.upc.edu].
Place of defense: Sala d'Audicions-EUOOT- Edifici TR8.
Place of preparation: EUOOT, EDIFICI TR8 DESPATX 217 Campus TERRASSA.

Summary: The sense of sight plays a crucial role in the relation of the human being with his environment, proportioning most of the information that he perceives from it. So the importance of the study of the quality of the eye as an imaging system is understandable. This study is clinically carried out by means of subjective measurements, or more recently, by the determination of the ocular wave aberration. However, there is a lack of clinical tools for the evaluation of ocular optical quality taking into account all the factors degrading the image on the retina (difraction, aberrations and intraocular scattering). Thus, the main objective of this thesis work consists of the development of a clinical instrument for the measurement of the eyeâs overall optical quality, based on the double-pass technique, complementing those measurements with aberrometric estimations. Therefore, the optical, mechanical and electronic design of a system based on the double-pass technique has been performed obtaining a totally automatized instrument prototype. A software tool has been implemented as well, permiting the control of the device, the register and analysis of the images, and the visualization of the results in a very simple way. It gives the user both qualitative and quantitative information (by means of the modulation transfer function MTF and several quality parameters) about the optical performance for far vision and different accommodative states. In this sense a method for the determination of the amplitude of accommodation has been developed making this instrument the only system capable of objectively measuring this magnitude. The instrument has been clinically validated. A second prototype has also been implemented that permits the analysis of the repetitiveness of the systemâs results. Additionally, two separate clinical studies have been carried out that demostrate the instrumentâs potential. In the first study, a method for estimating psicophysical parameters (visual acuity and contrast sensitivity) have been found using the MTF obtained form the double-pass images. The second study consisted in evaluating the amplitude of accommodation both in phakic and pseudophakic subjects. Finally, the estimations obtained with the double-pass instrument have been compared with those from an aberrometric system, finding, in the latter, an overestimation of quality in cases where intraocular scattering and high order aberrations are significant. A parameter which quantifies the level of intraocular scattering has been defined by comparing the estimations obtained for both techniques. Regarding the implemented aberrometric system, a new ocular wave-front sensor has been proposed and developed; this system conceptually solves the principal drawbacks affecting the current methods, principally the achievable order of aberration and the dynamic range. A curvature sensor, applied in astronomy and optical metrology, has been adapted for use in the case of the human eye. In order to test its feasibility, the sensor has been studied by means of computer simulations, analizing the performance of the sensor as a function of the characteristics of the image capture system (sensitivity, noise, bit depth, etc). This helped, as well, in the design of the optimal optical experimental set-up. Important innovations have been introduced in the algorithm for wavefront retrieval from the captured images, making it faster and more precise. This good performance has been confirmed with experimental measurements, both with artificial and real eyes. This new sensor can be easily incorporated into the double-pass instrument, obtaining in this way a system which characterizes all the factors of optical degradation of the retinal image. A design for this joint measurement system is proposed.

Author: Manzanera Román Silvestre.
Year: 2006.
University: MURCIA [www.um.es].
Place of defense: CENTRO DE INVESTIGACIÓN EN ÓPTICA Y NANOFÍSICA.
Place of preparation: Centro de Investigación en Óptica y Nanofísica.

Summary: A visual simulator (SV) is a system that allows the optical properties through which carries out the vision, simulating different conditions, and allowing study their effect. This can be based on adaptive optics systems, in which case we are dealing with the simulator visual adaptive optics (SVOA). In this work has been built and tested a tool that works as SVOA when working in monochromatic light, applied to the design and testing of profiles progressive phase to extend the depth of focus as solutions to the presbicia. It has perfected a SV in polychromatic, and in this case has been used in the study of the effect on the vision of chromatic aberration longitudinal and its coupling with spherical aberration. As an active element generator stages in the SVOA has employed a liquid crystal spatial modulator high resolution (PPM X8267UM-16 Hamamatsu). First has been carried out a study on the capabilities of modulator (generation, correction of aberrations, response times) for application on the eye. We have developed simulation procedures for the determination of phases that increase the depth of focus. Several of the profiles found progressive stage, where the depth of focus is known theoretically are induced modulator and analyzed in the SVOA, both objective and visually, resulting in all cases an excellent agreement. Finally some of these profiles were implemented physically in contact lenses and tested the depth of focus. The good agreement was found between this evaluation and simulating the profile obtained with SVOA validate the whole process and the system. The SV in polychromatic has been used to study the effect on vision when correcting chromatic aberration longitudinal (ACL) of the eye (with a new corrective type difraccional) and spherical aberration average residual found in subjects pseudoafáquicos, with a view to a redesign of intraocular lens. In order to measure in each case the existing ACL was used a new device based on an objective measure wavefront sensor of Hartmann-Shack, which uses white light lamp, and a series of filters interferenciales, with which it is possible get aberrations monochrome different wavelengths visible and the ACL. Also simultaneously using an alternative method subjective measurement. With these tools is characterized and controls the ACL induced by the concealer. We have undertaken measures of visual acuity and contrast sensitivity combining the correction of chromatic and spherical aberrations. The results indicate that the better quality of vision occurs at the same time to eliminate both aberrations.