The human eye is an example of robust optical design

Artal, Pablo; Benito, Antonio; Tabernero, Juan

doi:10.1167/6.1.1

Cited by 194 publications

(166 citation statements)

References 18 publications

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“…This is in agreement with several recent studies on compensation of horizontal coma between the anterior cornea and internal optics. [10][11] This is also consistent with the theoretical account on relationship between spherical aberration and coma aberration in a previous study. 12 But, surprising to us was the non-significant correlations between the y-axis pupil center shift and the vertical coma.…”

Section: Discussionsupporting

confidence: 91%

Association between Offset of the Pupil Center from the Corneal Vertex and Wavefront Aberration

Liu

et al. 2008

Journal of Optometry

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PURPOSE:To investigate the influence of offsets of the pupil center from the corneal vertex on wavefront aberrations in the anterior cornea and the whole eye. METHODS: Both right and left eyes of 103 subjects were measured for the wavefront aberrations in the anterior cornea, along with the offset of the pupil center relative to the corneal vertex, using a Humphrey corneal topographer, and for the wavefront aberration in the whole eye using a WASCA wavefront sensor. Correlations of the pupil center offsets with the Zernike aberrations were tested. RESULTS: X-axis shift of the pupil center from the corneal vertex was significantly correlated to horizontal coma for both the right (r = 0.54, P<0.0001) and left eyes (r=0.48, P<0.0001) in the cornea, but was weakly correlated to the coma in the whole eye (r=0.17, P=0.04 for OD; and r=0.17, P=0.05 for OS). Significant but weak correlations with the x-axis pupil center shift were also found for several other Zernike aberrations, including the oblique astigmatism, vertical trefoil and secondary astigmatism. Very few Zernike aberrations were significantly correlated to y-axis pupil center shift. Most Zernike aberrations were significantly correlated between the right and left eyes to produce bilateral symmetry in the cornea and the whole eye. CONCLUSIONS:The results suggest that offset of the pupil center from the corneal vertex plays an important role in determining horizontal coma and few other Zernike aberrations. Factors controlling bilateral symmetry of the wavefront aberrations between the two eyes could make important contributions to wavefront aberrations in the human eye. (J Optom 2008;1:8-13 ©2008 Spanish Council of Optometry) KEY WORDS: wavefront aberration; angle lambda; pupil center; corneal vertex; bilateral symmetry. RESUMEN OBJETIVO:Investigar el efecto que tiene el descentramiento de la pupila con respecto al vértice corneal sobre las aberraciones del frente onda asociadas tanto a la cara anterior de la córnea como a la totalidad del ojo. MÉTODOS: En los ojos derecho e izquierdo de 103 sujetos se midieron las aberraciones del frente de onda asociadas tanto a la cara anterior de la córnea (utilizando un topógrafo corneal Humphrey), como a la totalidad del ojo (utilizando un sensor de frente de onda WASCA). Asimismo, se midió el desplazamiento del centro de la pupila respecto a la posición del vértice corneal, utilizando el mismo topógrafo corneal Humphrey anteriormente mencionado. Se investigó la posible correlación entre el valor del desplazamiento del centro de la pupila y los distintos términos de aberraciones de Zernike. RESULTADOS: El desplazamiento según el eje x del centro de la pupila respecto al vértice corneal muestra una correlación significativa con el valor del coma horizontal en la córnea tanto para los ojos derechos (r=0,54; P<0,0001) como para los izquierdos (r=0,48; P<0,0001); sin embargo, existe una correlación muy débil entre el valor de este desplazamiento y el coma de toda la óptica ocular (r=0,17; P=0,04 para OD; y r=0,17; P...

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Section: Discussionsupporting

confidence: 91%

Association between Offset of the Pupil Center from the Corneal Vertex and Wavefront Aberration

Liu

et al. 2008

Journal of Optometry

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“…The brass housing of the laser diode was hot-glued to the outside of the gimbal's inner ring so that the relative position between the laser diode and the eye model was fixed. Note that we did not do an optical alignment, so there might be a small angle between the optical axis of the AE and the laser diode, which is consistent like angle kappa (kappa is the angle between the optical axis and the visual axis; Artal, Benito, & Tabernero, 2006). The distance from the exit pupil of the laser diode to the center of the AE was 17.5 mm.…”

Section: Calibration and Data Recordingmentioning

confidence: 60%

A study of artificial eyes for the measurement of precision in eye-trackers

et al. 2016

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The precision of an eye-tracker is critical to the correct identification of eye movements and their properties. To measure a system's precision, artificial eyes (AEs) are often used, to exclude eye movements influencing the measurements. A possible issue, however, is that it is virtually impossible to construct AEs with sufficient complexity to fully represent the human eye. To examine the consequences of this limitation, we tested currently used AEs from three manufacturers of eye-trackers and compared them to a more complex model, using 12 commercial eye-trackers. Because precision can be measured in various ways, we compared different metrics in the spatial domain and analyzed the power-spectral densities in the frequency domain. To assess how precision measurements compare in artificial and human eyes, we also measured precision using human recordings on the same eyetrackers. Our results show that the modified eye model presented can cope with all eye-trackers tested and acts as a promising candidate for further development of a set of AEs with varying pupil size and pupil-iris contrast. The spectral analysis of both the AE and human data revealed that human eye data have different frequencies that likely reflect the physiological characteristics of human eye movements. We also report the effects of sample selection methods for precision calculations. This study is part of the EMRA/COGAIN Eye Data Quality Standardization Project.Keywords Eye movements . Artificial eye . Precision . Data quality . Eye-tracker noise . Power-spectral density High-quality eye movement data are a prerequisite for the valid measurement of fixation durations, saccade amplitudes and velocities, and many other behavioral measures in eye movement research. Spatial accuracy and precision are two of the most important aspects of eye data quality. Accuracy is defined as the difference between the tracker-estimated gaze position and the actual gaze position, whereas precision is defined as the ability to reliably reproduce a measurement, given a fixating eye (ideally, a stable eye)-see Fig. 1. Accuracy and precision are two independent measurements of eye-tracking data quality-that is, they can be both good or poor, or one good and the other poor. The most commonly used measures of precision in eye-trackers are the sample-tosample root mean square angular displacement [RMS(S2S)] and the standard deviation (SD) of samples in a given time window. These values will change not only dependent on the actual precision level of the tracker but also on the calculation used, and the samples or time period included in that calculation. Longer periods increase the probability of fixational eye movements (tremor, microsaccades, and drift), which in turn will increase imprecision. Holmqvist, Nyström, and Mulvey (2012) showed that artificially increasing imprecision via the addition of Gaussian noise from 0.03°to 0.30°results in an increase of up to 200 ms in calculated fixation durations. If this range of noise, as measured by RMS(S2S) precis...

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“…design and optical performance of the eye. For instance, Von Helmholtz 4 would not accept a lens with the optical defects of the eye; whereas for Artal et al 101 the eye is an example of robust design. These apparently opposite comments reflect the paradoxical mixture of flaws and smart design principles and optical performance that the human eye exhibits; for example the symmetrical principle together with the total lack of symmetry of the optical surfaces and misalignment of the axes.…”

Section: Figure 13mentioning

confidence: 99%

“…With these "paradoxes" it is relatively simple to conciliate opposite comments regarding the eye. For instance a smart design principle (such as symmetry) with a poor optimization and implementation (lack of symmetry) will display large optical defects; 4 but this turns out to be robust 101 simply because the optical quality is poor enough to get much worse. Nevertheless, one might argue that the optical design of the eye is not too bad considering that its optical quality worsen when it is modified, for instance by surgery.…”

Section: Figure 13mentioning

confidence: 99%

The Optical Design of the Human Eye: a Critical Review

Navarro

2009

Journal of Optometry

100

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Cornea, lens and eye models are analyzed and compared to experimental findings to assess properties and eventually unveil optical design principles involved in the structure and function of the optical system of the eye. Models and data often show good match but also some paradoxes. The optical design seems to correspond to a wide angle lens. Compared to conventional optical systems, the eye presents a poor optical quality on axis, but a relatively good quality off-axis, thus yielding higher homogeneity for a wide visual field. This seems the result of an intriguing combination of the symmetry design principle with a total lack of rotational symmetry, decentrations and misalignments of the optical surfaces (J Optom 2009;2:3-18 ©2009 Spanish Council of Optometry) KEY WORDS: human eye's optical design; eye models; design principles; ocular aberrations; optical quality of the eye. RESUMENEn este trabajo, los modelos de córnea, de cristalino y de ojo se analizan y se comparan con los datos experimentales para evaluar las propiedades y, eventualmente, para desvelar los principios del diseño óptico que afectan a la estructura y al funcionamiento del sistema óptico del ojo humano. A menudo encontramos una coincidencia razonable entre los modelos y los datos experimentales, pero también se ponen de manifiesto algunas paradojas. El diseño óptico parece corresponderse con el de un gran angular. En comparación con los sistemas ópticos convencionales, el ojo tiene una mala calidad óptica en eje pero, por el contrario, presenta una calidad relativamente buena fuera de eje, proporcionando así una gran homogeneidad a una amplia extensión del campo visual. Este hecho parece ser el resultado de una curiosa combinación del principio de diseño simétrico con una total ausencia de simetría de rotación, con descentramientos y con una deficiente alineación de las superficies ópticas. (J Optom 2009;2:3-18 ©2009 Consejo General de Colegios de Ópticos-Optometristas de España) PALABRAS CLAVE: diseño óptico del ojo humano; modelos de ojo; principios de diseño; aberraciones oculares; calidad óptica del ojo.

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The human eye is an example of robust optical design

Cited by 194 publications

References 18 publications

Association between Offset of the Pupil Center from the Corneal Vertex and Wavefront Aberration

Association between Offset of the Pupil Center from the Corneal Vertex and Wavefront Aberration

A study of artificial eyes for the measurement of precision in eye-trackers

The Optical Design of the Human Eye: a Critical Review

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