Antonio Benito | Universidad de Murcia (original) (raw)
Papers by Antonio Benito
Optics Express, 2006
A compact and robust instrument for measuring the alignment of ocular surfaces has been designed ... more A compact and robust instrument for measuring the alignment of ocular surfaces has been designed and used in living eyes. It is based on recording Purkinje images (reflections of light at the ocular surfaces) at nine different angular fixations. A complete analysis on the causes of misalignments of Purkinje images and its relations with those physical variables to be measured (global eye tilt, lens decentration and lens tilt) is presented. A research prototype based on these ideas was built and tested in normal and pseudophakic eyes (after cataract surgery). The new analysis techniques, together with the semicircular extended source and multiple fixation tests that we used, are significant improvements towards a robust approach to measuring the misalignments of the ocular surfaces in vivo. This instrument will be of use in both basic studies of the eye's optics and clinical ophthalmology.
Optometry and Vision Science, 2003
Purpose. Outstanding improvements in vision can theoretically be expected using contact lenses th... more Purpose. Outstanding improvements in vision can theoretically be expected using contact lenses that correct monochromatic aberrations of the eye. Imperfections in such correction inherent to contact lenses are lens flexure, translation, rotation, and tear layer effects. The effects of pupil size and accommodation on ocular aberration may cause further difficulties. The purpose of this study was to evaluate whether nonaxisymmetric soft contact lenses could efficiently compensate for higher-order aberrations induced by keratoconus and to what extent rotation and translation of the lens would degrade this perfect correction. Methods. Height topography data of nine moderate to severe keratoconus corneas were obtained using the Maastricht Shape Topographer. Three-dimensional ray tracing was applied to each elevation topography to calculate aberrations in the form of a phase error mapping. The effect of a nonaxisymmetric soft contact lens tailored to the corneal aberrations was simulated by adding an opposite phase error mapping that would theoretically compensate all corneal-induced optical aberrations of the keratoconus eyes. Translation (0.25, 0.5, 0.75, and 1.0 mm) and rotation (2.5°, 5.0°, 7.5°, and 10°) mismatches were introduced. The modulation transfer function (MTF) of each eye with each displaced correction and with various pupil sizes (3, 5, and 7 mm) was deduced from the residual phase error mapping. A single performance criterion (mtfA) was calculated as the area under the MTF over a limited spatial frequency range (5 to 15 periods per degree). Finally, the ratio (RmtfA) of corrected mtfA over uncorrected mtfA provided an estimate of the global enhancement in contrast sensitivity with the customized lens. Results. The contrast improvement ratios RmtfA with perfectly located lenses were for an average pupil size of 4.5 mm between 6.5 and 200. For small translation errors (0.25 mm), RmtfA ranged between 2 and 7. The largest lens translation tested (1 mm) often resulted in poorer performance than without correction (RmtfA <1). More than threefold improvements were achieved with any of the angular errors experimented. RmtfA values showed significant variations for pupil diameters between 3 and 7 mm. Conclusions. Three-dimensional aberration-customized soft contact lenses may drastically improve visual performance in patients with keratoconus. However, such lenses should be well positioned on the cornea. In particular, translation errors should not exceed 0.5 mm. Angular errors appeared to be less critical. It is further questioned whether the visual system is able to adapt to variations in optical performance of the correction in situ due to lens positioning and pupil size. (Optom Vis Sci 2003;80:637-643)
Wavefront sensors provide quite useful information on the optical quality of the eye. However, in... more Wavefront sensors provide quite useful information on the optical quality of the eye. However, in eyes where very high-order aberrations and scattered light are prominent, wavefront sensors may overestimate retinal image quality. This study showed that, in those cases, the double-pass technique is a complementary tool for better estimation of ocular optical quality.
Vision Research, 2002
Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. ... more Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. The wave-front aberration were obtained under natural conditions using a near-infrared Shack-Hartmann wave-front sensor. For this population and a 5 mm pupil, more than 99% of the root-mean square wave-front error is contained in the first four orders of a Zernike expansion and about 91% corresponds only to the second order. Comparison of wave-fronts aberrations from right and left eye in 35 subjects, showed a good correlation between most of the second-and third-order terms and a slight (but not clear) tendency for mirror symmetry between eyes. Ó
To use powerful modeling techniques for predicting the optical performance of eyes implanted with... more To use powerful modeling techniques for predicting the optical performance of eyes implanted with different types of intraocular lenses (IOLs). This approach will allow performance of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual cataract surgery,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; with different IOL designs that can be used and physical parameters that may occur during actual surgery-in particular, in IOLs that correct spherical aberration. A computer model was developed to predict the optical performance of individual eyes after IOL implantation. The approach was validated in a group of patients with eyes implanted with different IOLs. In these patients, corneal wavefront aberrations were calculated from elevations provided by videokeratography. Ocular aberrations were measured with a high-dynamic range Hartmann-Shack wavefront sensor. Misalignments (IOL tilt and decentration) were estimated with a new instrument, based on recording Purkinje images. This model of particular corneal aberrations and IOL parameters (intrinsic optical design details plus geometric location data) was used to estimate the total ocular aberrations after surgery and to compared them with actual aberrations measured directly with the wavefront sensor. The aberrations of implanted eyes predicted by the individualized optical models were well correlated with the actual aberration measured in each subject. This result indicates that the approach is adequate in evaluating the actual optical performance of different types of lenses. The model allows a large number of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; surgeries to be performed, to test the performance of current or future IOL designs. A &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual surgery&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; approach was designed to predict the optical performance in pseudophakic eyes. In each subject, it was possible to obtain the eye&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s optical performance with a particular IOL and biometric data after surgery. Specifically, this modeling can be used to evaluate the tolerances to misalignments and depth of focus of IOLs correcting spherical aberration in actual eyes. This approach is quite powerful and is especially applicable to the study of current and future aberration-correction IOL designs.
Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. ... more Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. The wave-front aberration were obtained under natural conditions using a near-infrared Shack-Hartmann wave-front sensor. For this population and a 5 mm pupil, more than 99% of the root-mean square wave-front error is contained in the first four orders of a Zernike expansion and about 91% corresponds only to the second order. Comparison of wave-fronts aberrations from right and left eye in 35 subjects, showed a good correlation between most of the second-and third-order terms and a slight (but not clear) tendency for mirror symmetry between eyes. Ó
Journal of The Optical Society of America A-optics Image Science and Vision, 2007
We studied the mechanism of compensation of aberrations within the young human eye by using exper... more We studied the mechanism of compensation of aberrations within the young human eye by using experimental data and advanced ray-tracing modeling. Corneal and ocular aberrations along with the alignment properties (angle kappa, lens tilt, and decentration) were measured in eyes with different refractive errors. Predictions from individualized ray-tracing optical models were compared with the actual measurements. Ocular spherical aberration was, in general, smaller than corneal spherical aberration without relation to refractive error. However, horizontal coma compensation was found to be significantly larger for hyperopic eyes where angle kappa tended to also be larger. We propose a simple analytical model of the relationship between the corneal coma compensation effect with the field angle and corneal and crystalline shape factors. The actual shape factors corresponded approximately to the optimum shapes that automatically provide this coma compensation. We showed that the eye behaves as an aplanatic optical system, an optimized design solution rendering stable retinal image quality for different ocular geometries.
Journal of Vision, 2006
In most eyes, in the fovea and at best focus, the resolution capabilities of the eye's optics and... more In most eyes, in the fovea and at best focus, the resolution capabilities of the eye's optics and the retinal mosaic are remarkably well adapted. Although there is a large individual variability, the average magnitude of the high order aberrations is similar in groups of eyes with different refractive errors. This is surprising because these eyes are comparatively different in shape: Myopic eyes are longer whereas hyperopic eyes are shorter. In most young eyes, the amount of aberrations for the isolated cornea is larger than for the complete eye, indicating that the internal ocular optics (mainly the crystalline lens) play a signif icant role in compensating for the corneal aberrations, thereby producing an improved retinal image. In this paper, we show that this compensation is larger in the less optically centered eyes that mostly correspond to hyperopic eyes. This suggests a type of mechanism in the eye's design that is the most likely responsible for this compensation. Spherical aberration of the cornea is partially compensated by that of the lens in most eyes. Lateral coma is also compensated mainly in hyperopic eyes. We found that the distribution of aberrations between the cornea and lens appears to allow the optical properties of the eye to be relatively insensitive to variations arising from eye growth or exact centration and alignment of the eye's optics relative to the fovea. These results may suggest the presence of an auto-compensation mechanism that renders the eye's optics robust despite large variation in the ocular shape and geometry.
Optics Express, 2006
A compact and robust instrument for measuring the alignment of ocular surfaces has been designed ... more A compact and robust instrument for measuring the alignment of ocular surfaces has been designed and used in living eyes. It is based on recording Purkinje images (reflections of light at the ocular surfaces) at nine different angular fixations. A complete analysis on the causes of misalignments of Purkinje images and its relations with those physical variables to be measured (global eye tilt, lens decentration and lens tilt) is presented. A research prototype based on these ideas was built and tested in normal and pseudophakic eyes (after cataract surgery). The new analysis techniques, together with the semicircular extended source and multiple fixation tests that we used, are significant improvements towards a robust approach to measuring the misalignments of the ocular surfaces in vivo. This instrument will be of use in both basic studies of the eye's optics and clinical ophthalmology.
Optometry and Vision Science, 2003
Purpose. Outstanding improvements in vision can theoretically be expected using contact lenses th... more Purpose. Outstanding improvements in vision can theoretically be expected using contact lenses that correct monochromatic aberrations of the eye. Imperfections in such correction inherent to contact lenses are lens flexure, translation, rotation, and tear layer effects. The effects of pupil size and accommodation on ocular aberration may cause further difficulties. The purpose of this study was to evaluate whether nonaxisymmetric soft contact lenses could efficiently compensate for higher-order aberrations induced by keratoconus and to what extent rotation and translation of the lens would degrade this perfect correction. Methods. Height topography data of nine moderate to severe keratoconus corneas were obtained using the Maastricht Shape Topographer. Three-dimensional ray tracing was applied to each elevation topography to calculate aberrations in the form of a phase error mapping. The effect of a nonaxisymmetric soft contact lens tailored to the corneal aberrations was simulated by adding an opposite phase error mapping that would theoretically compensate all corneal-induced optical aberrations of the keratoconus eyes. Translation (0.25, 0.5, 0.75, and 1.0 mm) and rotation (2.5°, 5.0°, 7.5°, and 10°) mismatches were introduced. The modulation transfer function (MTF) of each eye with each displaced correction and with various pupil sizes (3, 5, and 7 mm) was deduced from the residual phase error mapping. A single performance criterion (mtfA) was calculated as the area under the MTF over a limited spatial frequency range (5 to 15 periods per degree). Finally, the ratio (RmtfA) of corrected mtfA over uncorrected mtfA provided an estimate of the global enhancement in contrast sensitivity with the customized lens. Results. The contrast improvement ratios RmtfA with perfectly located lenses were for an average pupil size of 4.5 mm between 6.5 and 200. For small translation errors (0.25 mm), RmtfA ranged between 2 and 7. The largest lens translation tested (1 mm) often resulted in poorer performance than without correction (RmtfA <1). More than threefold improvements were achieved with any of the angular errors experimented. RmtfA values showed significant variations for pupil diameters between 3 and 7 mm. Conclusions. Three-dimensional aberration-customized soft contact lenses may drastically improve visual performance in patients with keratoconus. However, such lenses should be well positioned on the cornea. In particular, translation errors should not exceed 0.5 mm. Angular errors appeared to be less critical. It is further questioned whether the visual system is able to adapt to variations in optical performance of the correction in situ due to lens positioning and pupil size. (Optom Vis Sci 2003;80:637-643)
Wavefront sensors provide quite useful information on the optical quality of the eye. However, in... more Wavefront sensors provide quite useful information on the optical quality of the eye. However, in eyes where very high-order aberrations and scattered light are prominent, wavefront sensors may overestimate retinal image quality. This study showed that, in those cases, the double-pass technique is a complementary tool for better estimation of ocular optical quality.
Vision Research, 2002
Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. ... more Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. The wave-front aberration were obtained under natural conditions using a near-infrared Shack-Hartmann wave-front sensor. For this population and a 5 mm pupil, more than 99% of the root-mean square wave-front error is contained in the first four orders of a Zernike expansion and about 91% corresponds only to the second order. Comparison of wave-fronts aberrations from right and left eye in 35 subjects, showed a good correlation between most of the second-and third-order terms and a slight (but not clear) tendency for mirror symmetry between eyes. Ó
To use powerful modeling techniques for predicting the optical performance of eyes implanted with... more To use powerful modeling techniques for predicting the optical performance of eyes implanted with different types of intraocular lenses (IOLs). This approach will allow performance of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual cataract surgery,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; with different IOL designs that can be used and physical parameters that may occur during actual surgery-in particular, in IOLs that correct spherical aberration. A computer model was developed to predict the optical performance of individual eyes after IOL implantation. The approach was validated in a group of patients with eyes implanted with different IOLs. In these patients, corneal wavefront aberrations were calculated from elevations provided by videokeratography. Ocular aberrations were measured with a high-dynamic range Hartmann-Shack wavefront sensor. Misalignments (IOL tilt and decentration) were estimated with a new instrument, based on recording Purkinje images. This model of particular corneal aberrations and IOL parameters (intrinsic optical design details plus geometric location data) was used to estimate the total ocular aberrations after surgery and to compared them with actual aberrations measured directly with the wavefront sensor. The aberrations of implanted eyes predicted by the individualized optical models were well correlated with the actual aberration measured in each subject. This result indicates that the approach is adequate in evaluating the actual optical performance of different types of lenses. The model allows a large number of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; surgeries to be performed, to test the performance of current or future IOL designs. A &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;virtual surgery&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; approach was designed to predict the optical performance in pseudophakic eyes. In each subject, it was possible to obtain the eye&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s optical performance with a particular IOL and biometric data after surgery. Specifically, this modeling can be used to evaluate the tolerances to misalignments and depth of focus of IOLs correcting spherical aberration in actual eyes. This approach is quite powerful and is especially applicable to the study of current and future aberration-correction IOL designs.
Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. ... more Monochromatic ocular aberrations in 108 eyes of a normal young population (n ¼ 59) were studied. The wave-front aberration were obtained under natural conditions using a near-infrared Shack-Hartmann wave-front sensor. For this population and a 5 mm pupil, more than 99% of the root-mean square wave-front error is contained in the first four orders of a Zernike expansion and about 91% corresponds only to the second order. Comparison of wave-fronts aberrations from right and left eye in 35 subjects, showed a good correlation between most of the second-and third-order terms and a slight (but not clear) tendency for mirror symmetry between eyes. Ó
Journal of The Optical Society of America A-optics Image Science and Vision, 2007
We studied the mechanism of compensation of aberrations within the young human eye by using exper... more We studied the mechanism of compensation of aberrations within the young human eye by using experimental data and advanced ray-tracing modeling. Corneal and ocular aberrations along with the alignment properties (angle kappa, lens tilt, and decentration) were measured in eyes with different refractive errors. Predictions from individualized ray-tracing optical models were compared with the actual measurements. Ocular spherical aberration was, in general, smaller than corneal spherical aberration without relation to refractive error. However, horizontal coma compensation was found to be significantly larger for hyperopic eyes where angle kappa tended to also be larger. We propose a simple analytical model of the relationship between the corneal coma compensation effect with the field angle and corneal and crystalline shape factors. The actual shape factors corresponded approximately to the optimum shapes that automatically provide this coma compensation. We showed that the eye behaves as an aplanatic optical system, an optimized design solution rendering stable retinal image quality for different ocular geometries.
Journal of Vision, 2006
In most eyes, in the fovea and at best focus, the resolution capabilities of the eye's optics and... more In most eyes, in the fovea and at best focus, the resolution capabilities of the eye's optics and the retinal mosaic are remarkably well adapted. Although there is a large individual variability, the average magnitude of the high order aberrations is similar in groups of eyes with different refractive errors. This is surprising because these eyes are comparatively different in shape: Myopic eyes are longer whereas hyperopic eyes are shorter. In most young eyes, the amount of aberrations for the isolated cornea is larger than for the complete eye, indicating that the internal ocular optics (mainly the crystalline lens) play a signif icant role in compensating for the corneal aberrations, thereby producing an improved retinal image. In this paper, we show that this compensation is larger in the less optically centered eyes that mostly correspond to hyperopic eyes. This suggests a type of mechanism in the eye's design that is the most likely responsible for this compensation. Spherical aberration of the cornea is partially compensated by that of the lens in most eyes. Lateral coma is also compensated mainly in hyperopic eyes. We found that the distribution of aberrations between the cornea and lens appears to allow the optical properties of the eye to be relatively insensitive to variations arising from eye growth or exact centration and alignment of the eye's optics relative to the fovea. These results may suggest the presence of an auto-compensation mechanism that renders the eye's optics robust despite large variation in the ocular shape and geometry.