Begoña Domenech

Publications (10) View all

• Article: Blinking kinematics description through non-invasive measurement

  Jorge Perez, Julian Espinosa, Begoña Domenech, David Mas, Carlos Illueca
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  ABSTRACT: Spontaneous eye blinking is a complex process, which implies the joint actions of the eyelid muscles and the eye globe. These actions provoke the eyelid closure and simultaneous eye retraction into the orbit. Recently, the authors presented a non-invasive technique for measuring both movements that permits calculating several parameters. Following the work from Malbouisson and co-workers, we have fitted the displacement curves of the eyelid to an analytical function and, additionally, we have extended the kinematic model to the eye retraction movements. As a result of the fitting, some dynamic parameters have been presented for the first time in the literature. This study can be easily extended to obtain relevant information about ocular biomechanical properties in physiological optics and provides results that may be of interest in neurophysiology, in order to understand the blinking mechanism.
  Journal of Modern Optics 11/2011; 58(Nos. 19–20):1857-1863. · 1.17 Impact Factor
• Source

  Available from: Julián Espinosa

  Article: Correlation between the dioptric power, astigmatism and surface shape of the anterior and posterior corneal surfaces.

  David Mas, Julian Espinosa, Begoña Domenech, Jorge Perez, Henryk Kasprzak, Carlos Illueca
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  ABSTRACT: A knowledge of the shape of the cornea is of major importance for the planning and monitoring of surgery, and for the correct diagnosis of corneal diseases. Many authors have studied the geometry of the second corneal surface in the central region and it has been stated that there is a high correlation between the central radii of curvature and asphericities of the two corneal surfaces. In this work we extend this study to a larger, central, 6 mm diameter of the cornea. Surface height data, obtained with an Oculus Pentacam from 42 eyes of 21 subjects, were analysed to yield surface power vectors. Corneal heights of both surfaces were also decomposed into low-order Zernike polynomials and the correlations between each of the power vectors and low-order Zernike coefficients for the two surfaces were studied. There was not only a strong correlation between spherical powers and Zernike defocus coefficients, but also between the astigmatic components. The correspondence between the astigmatism in both surfaces found here can be of the utmost importance in planning optical surgery, since perfect spherical ablation of the first surface does not assure total correction of corneal astigmatism.
  Ophthalmic and Physiological Optics 06/2009; 29(3):219-26. · 1.58 Impact Factor
• Article: The effect of pupil and observation distance on the contrast sensitivity function.

  C Hernández, B Doménech, M M Seguí, C Illueca
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  ABSTRACT: Measuring the contrast sensitivity function (CSF) is becoming more frequent in the analyses that are routinely done in optometric practice. This measurement is generally done in far vision, and the observation distance and its effects are not considered to significantly alter this function. Among these effects we should point out the accommodation of the visual optical system to the stimulus and the errors in accommodation associated with this, changes in pupil diameter and therefore in retinal illumination when the observation distance changes, the different level of aberrations (spherical aberration, astigmatism) for different cases, and so on. All of these factors contribute to the fact that the contrast sensitivity of a visual system varies according to the accommodative stimulus. In this study we attempt to clarify the influence of these different parameters by evaluating the CSF for three observation distances. The study was done in monocular vision, with a natural pupil and with a 3 mm artificial pupil that made it possible to maintain the same level of retinal illumination for all distances.
  Ophthalmic and Physiological Optics 08/1996; 16(4):336-41. · 1.58 Impact Factor
• Article: Repeatability and reproducibility of corneal thickness using SOCT Copernicus HR.

  Silvia Vidal, Valentín Viqueira, David Mas, Begoña Domenech
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  ABSTRACT: PURPOSE: The aim of this study is to determine the reliability of corneal thickness measurements derived from SOCT Copernicus HR (Fourier domain OCT). METHODS: Thirty healthy eyes of 30 subjects were evaluated. One eye of each patient was chosen randomly. Images were obtained of the central (up to 2.0 mm from the corneal apex) and paracentral (2.0 to 4.0 mm) cornea. We assessed corneal thickness (central and paracentral) and epithelium thickness. The intra-observer repeatability data were analysed using the intra-class correlation coefficient (ICC) for a range of 95 per cent within-subject standard deviation (S(W) ) and the within-subject coefficient of variation (C(W) ). The level of agreement by Bland-Altman analysis was also represented for the study of the reproducibility between observers and agreement between methods of measurement (automatic versus manual). RESULTS: The mean value of the central corneal thickness (CCT) was 542.4 ± 30.1 μm (SD). There was a high intra-observer agreement, finding the best result in the central sector with an intra-class correlation coefficient of 0.99, 95 per cent CI (0.989 to 0.997) and the worst, in the minimum corneal thickness, with an intra-class correlation coefficient of 0.672, 95 per cent CI (0.417 to 0.829). Reproducibility between observers was very high. The best result was found in the central sector thickness obtained both manually and automatically with an intra-class correlation coefficient of 0.990 in both cases and the worst result in the maximum corneal thickness with an intra-class correlation coefficient of 0.827. The agreement between measurement methods was also very high with intra-class correlation coefficient greater than 0.91. On the other hand the repeatability and reproducibility for epithelial measurements was poor. CONCLUSION: Pachymetric mapping with SOCT Copernicus HR was found to be highly repeatable and reproducible. We found that the device lacks an appropriate ergonomic design as proper focusing of the laser beam onto the cornea for anterior segment scanning required that patients were positioned slightly farther away from the machine head-rest than in the setup for retinal imaging.
  Clinical and Experimental Optometry 01/2013; · 1.05 Impact Factor
• Article: Variation of the visual acuity--luminance function with background colour.

  B Domenech, M M Seguí, P Capilla, C Illueca
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  ABSTRACT: The relationship between visual acuity (VA) and background colour is a question that still creates a certain amount of confusion even today, although most authors agree that colour background does not basically affect VA, or at best, values that are only slightly better are obtained with monochromatic yellow light. The object of this paper is to try to clarify if, when the axial chromatic aberration (ACA) has been compensated for, certain differences due exclusively to colour persist or not. In order for this, the VA-luminance functions with red, green, blue and white backgrounds have been measured for two emmetropic observers, before and after compensating for the ACA. The results show that after the compensation, the curve corresponding to red is above the one corresponding to blue, with the one corresponding to green in between. The achromatic function (white background) practically overlaps with the green one. This behaviour is consistent with that shown recently for contrast sensitivity functions (CSFs). However, the asymptotic values are identical for the three colours, and so, it is understandable that no significant differences are normally found when only a standard measurement of VA is taken using the typical illumination from an optotype projector.
  Ophthalmic and Physiological Optics 08/1994; 14(3):302-5. · 1.58 Impact Factor