Consuelo Hernández
University of Alicante
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Featured researches published by Consuelo Hernández.
Journal of Modern Optics | 2005
Jorge Pérez; David Mas; Carlos Illueca; Juan Jose Miret; Carmen Vázquez; Consuelo Hernández
Realistic mathematical models are of great importance for studying the optical performance of the human eye. Light propagation algorithms provide robust methods to calculate field distributions inside a homogeneous medium, and thus they can be applied to the study of light patterns inside the anterior and posterior chambers of the eye. Dealing with real eyes implies using very short propagation distances together with highly refractive power surfaces. Thus, the general solutions of the field equation are used instead of paraxial Fresnel solutions. Conditions of application and sampling conditions of the method are clearly stated here. Numerical evaluation of the different refractive surfaces is also analysed. The main result is that a complete algorithm to obtain light patterns at any axial distance inside the eye is proposed. The method uses real corneal measures and axial distances together with crystalline models. Statistical results and individual predictions show the validity of the model. Application of the method is illustrated with the study of a bifocal intraocular lens.
Ophthalmic and Physiological Optics | 1998
Carlos Illueca; Carmen Vázquez; Consuelo Hernández; V. Viqueira
The interference technique of Newtons Rings is widely used for the quality control of optical surfaces because the precision obtained with this method proves to be very satisfactory. The dimensions of the rings permits calculation of the radii of curvature of the analysed surfaces and deformation of the interference pattern can be utilised to calculate other parameters, such as astigmatism. We describe the study of progressive surfaces by means of this technique, whereby the analysis of the various points of the progressive corridor is made, and also include information on the power function for these lenses, as well as the addition and corridor length.
Journal of Modern Optics | 2003
David Mas; Jorge Pérez; Carmen Vázquez; Consuelo Hernández; Carlos Illueca
A procedure to determine the best image range of distances that can be obtained from an aphakic eye is presented. Corneal surfaces are calculated from videokeratographic data. Light distributions at different distances inside the eye are calculated with a near-field Fresnel diffraction algorithm. These patterns are evaluated using three different quality functions which quantify the appearance of the energy distributions in each plane. Local extremes in those functions will serve to locate relevant distributions as Sturm focal planes and even the best image plane which is affordable by the cornea. The study is applied to strongly aberrated corneas.
Ophthalmic and Physiological Optics | 1992
Carlos Illueca; Consuelo Hernández; Begoña Domenech
In this article, a method for measuring the astigmatism produced by an oblique central refraction is proposed. Measurements were taken using two different values of the pantoscopic angle that can be produced by lenses mourned in frames. We show that in sped lie cases, and as a function of the angle and power of the lens, the resulting astigmatism can surpass the tolerance level of the eye.
Congress on Optics and Optoelectronics | 2005
David Mas; Jorge Pérez; Carlos Illueca; Julián Espinosa; Consuelo Hernández; Carmen Vázquez; Juan Jose Miret
In this communication, the authors have determined the longitudinal chromatic aberrations in real eyes. The method that has been used combines real data of corneal morphology, central thickness of crystalline lens and biometric measures of axial length together with numerical calculation of the propagation process. The curvature of the crystalline lens has been adjusted to different curvature models and refractive index distributions. The wavelength dependence of all ocular media has been modelled through the Cauchy formula. Propagation through anterior and posterior chambers has been accomplished through numerical calculation of diffraction integral instead of classical ray-tracing approach. This imposes serous restrictions on the number of samples that are needed for a full propagation process. If we are only interested in amplitude calculations the method consists of evaluating propagation from cornea to crystalline lens with a spectrum propagation method. Propagation from the lens to the best image plane is accomplished by a direct calculation of Fresnel integral. With this model, we have obtained the refraction chromatic difference in diopters for several eyes. Results are compared with real measures of the chromatic aberration, showing a good agreement with numerical calculations. The capabilities of the technique have been demonstrated by applying the method to the study of the chromatic aberration of a keratoconus.
Proceedings of SPIE | 2012
Julián Espinosa; Ana B. Roig; David Mas; Consuelo Hernández; Carlos Illueca
We present a new algorithm to process captured images of reflected Placido rings. Up to our knowledge, conventional topographers transform from Cartesian to polar coordinates and vice-versa, thus extrapolating corneal data and introducing noise and image artefacts. Moreover, captured data are processed by the device according to proprietary algorithms and offering a final map of corneal curvature. Corneal topography images consists of concentric rings of approximately elliptical shape. Our proposal consists of considering the information that provides each separate ring. A snake-annealing-like method permits identifying the ring even with discontinuities due to eye-lashes and reflections. By analysing the geometrical parameters of rings (centre, semi-axis and orientation), one can obtain information about small morphological micro-fluctuations and local astigmatisms. These parameters can be obtained with sub-pixel accuracy so the method results of high precision. The method can be easily adapted to work on any topographer, so that it can provide additional information about the cornea at no additional cost.
19th Congress of the International Commission for Optics: Optics for the Quality of Life | 2003
Consuelo Hernández; Carmen Vázquez; Carlos Illueca; David Mas; Jorge Pérez
The cornea may be considered as the major contributor to the ocular aberrations. For normal corneas working with parallel beams, the best image plane correspond to the image distribution in the focal plane. Working with highly deformed corneas, the focal plane is not well defined and thus further analysis has to be done. Different light distribution propagated from the cornea will be analyzed here. In order to evaluate these patterns we propose three different simple parameters that will provide useful information at low computational cost. The method can be applied in optometry clinics. Since it would be convenient to optimize the image formation process by a correcting lens before performing any surgical process over the cornea.
19th Congress of the International Commission for Optics: Optics for the Quality of Life | 2003
Jorge Pérez; David Mas; Carmen Vázquez; Consuelo Hernández; Carlos Illueca
Obtention of the phase transmittance of the cornea under the paraxial assumption does not provide accurate estimation of the corneal aberrations for wide apertures of the pupil. On the other hand, exact ray tracing will require a huge amount of calculations and does not provide uniform sampling of the energy distribution at the output. We propose to use a simple approximation that takes into account non-paraxial effects. This approximation allow obtention of a well sampled output plane at no additional computational cost.
Optics Communications | 2003
David Mas; Jorge Pérez; Consuelo Hernández; Carmen Vázquez; Juan Jose Miret; Carlos Illueca
Optik | 2005
Jorge Pérez; David Mas; Juan Jose Miret; Carmen Vázquez; Consuelo Hernández; Carlos Illueca