Equivalent Refractive Index of the Human Lens upon Accommodative Response

Hermans, E.A.; Dubbelman, M.; Heijde, Rob G.L. van der; Heethaar, R.M.

doi:10.1097/opx.0b013e31818e8d57

Cited by 31 publications

(42 citation statements)

References 9 publications

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“…036 63 In agreement with previous findings, we have found that a rather constant value of the parameters defining the GRIN best fitted the experimental data 9,35 and that the equivalent refractive index did not change with accommodation. 9,34,35 Despite the simplicity of the GRIN model, the estimated parameters allow reproducing the experimental input data with great accuracy (mean RMS < 40 lm), for all accommodation levels, using our recently developed optimization method based on OCT imaging. 28 Previous studies with simpler GRIN models suggested that no change in the parameters of the model was needed to account for a change of power of the crystalline lens with accommodation.…”

Section: Discussionsupporting

confidence: 80%

“…33,34 The relative contribution of the GRIN to lens power appears to remain constant with accommodation. 9,34,35 This suggests that a homogenous index material in lens refilling procedure would be equally efficient in producing a refractive power change (assuming identical lens shape changes) than the natural lens GRIN material. However, the impact of the GRIN in the lens high order aberrations and their change with accommodation has never been studied experimentally.…”

Section: Resultsmentioning

confidence: 99%

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Influence of Shape and Gradient Refractive Index in the Accommodative Changes of Spherical Aberration in Nonhuman Primate Crystalline Lenses

Castro

Birkenfeld

Maceo

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. To estimate changes in surface shape and gradient refractive index (GRIN) profile in primate lenses as a function of accommodation. To quantify the contribution of surface shape and GRIN to spherical aberration changes with accommodation. METHODS.Crystalline lenses from 15 cynomolgus monkeys were studied in vitro under different levels of accommodation produced by a stretching system. Lens shape was obtained from optical coherence tomography (OCT) cross-sectional images. The GRIN was reconstructed with a search algorithm using the optical path measured from OCT images and the measured back focal length. The spherical aberration of the lens was estimated as a function of accommodation using the reconstructed GRIN and a homogeneous refractive index. RESULTS.The lens anterior and posterior radii of curvature decreased with increasing lens power. Both surfaces exhibited negative asphericities in the unaccommodated state. The anterior surface conic constant shifted toward less negative values with accommodation, while the value of the posterior remained constant. GRIN parameters remained constant with accommodation. The lens spherical aberration with GRIN distribution was negative and higher in magnitude than that with a homogeneous equivalent refractive index (by 29% and 53% in the unaccommodated and fully accommodated states, respectively). Spherical aberration with the equivalent refractive index shifted with accommodation toward negative values (À0.070 lm/diopter [D]), but the reconstructed GRIN shifted it farther (À0.124 lm/ D).CONCLUSIONS. When compared with the lens with the homogeneous equivalent refractive index, the reconstructed GRIN lens has more negative spherical aberration and a larger shift toward more negative values with accommodation.

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Section: Discussionsupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Influence of Shape and Gradient Refractive Index in the Accommodative Changes of Spherical Aberration in Nonhuman Primate Crystalline Lenses

Castro

Birkenfeld

Maceo

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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“…The corneal refractive index was taken as 1.376, the aqueous humor refractive index as 1.336, and the crystalline lens refractive index was obtained from the age-dependent average refractive index expression derived by Uhlhorn et al (1.4104-1.4113 for the subjects of our study) [42]. A constant refractive index was used for all the accommodative demands since the equivalent refractive index does not change significantly during accommodation [43,44]. Optical distortion correction by the corneal surfaces (for the anterior lens) and corneal and anterior lens surfaces (for the posterior surface) were corrected using 3-D ray tracing routines, as described by Ortiz et al [30].…”

Section: Image Processingmentioning

confidence: 99%

Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT

Gambra

Ortíz

Pérez-Merino

et al. 2013

Biomed. Opt. Express

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Custom high-resolution high-speed anterior segment spectral domain Optical Coherence Tomography (OCT) provided with automatic quantification and distortion correction algorithms was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo in four subjects, for accommodative demands between 0 to 6 D in 1 D steps. Biol. Cybern. 54(3), 189-194 (1986a). 11. C. Miege and P. Denieul, "Mean response and oscillations of accommodation for various stimulus vergences in relation to accommodation feedback control," Ophthalmic Physiol. Opt. 8(2), 165-171 (1988). 12. L. F. Garner and M. K. Yap, "Changes in ocular dimensions and refraction with accommodation," Ophthalmic Physiol. Opt. 17(1), 12-17 (1997). 13. P. Rosales, M. Dubbelman, S. Marcos, and R. van der Heijde, "Crystalline lens radii of curvature from Purkinje and Scheimpflug imaging," J. Vis. 6(10), 1057-1067 (2006), http://www.journalofvision.org/6/10/5. 14. N. Brown, "The change in shape and internal form of the lens of the eye on accommodation," Exp. Eye Res.15 ( Ohbayashi, and K. Shimizu, "Full-range imaging of eye accommodation by high-speed long-depth range optical frequency domain imaging," Biomed.

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“…63,65 Different types of GRIN distributions yield totally different predictions 27,29 of optical performance. More recent studies, 68,69 suggest that the contribution of the GRIN distribution to the optical performance of the eye may be modest compared to earlier assumptions.…”

Section: Model Predictionsmentioning

confidence: 95%

“…In this case, the actual contribution of the GRIN structure will be much lower. A recent study by Hermans et al 68 suggests that the impact of the GRIN structure is modest. These authors even claim that they can model accommodation with a simple lens model under the assumption that both cortex and nucleus have different but homogeneous refractive indexes.…”

Section: Power (D) Model Fit Error (μM)mentioning

confidence: 99%

The Optical Design of the Human Eye: a Critical Review

Navarro

2009

Journal of Optometry

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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.

show abstract

Equivalent Refractive Index of the Human Lens upon Accommodative Response

Cited by 31 publications

References 9 publications

Influence of Shape and Gradient Refractive Index in the Accommodative Changes of Spherical Aberration in Nonhuman Primate Crystalline Lenses

Influence of Shape and Gradient Refractive Index in the Accommodative Changes of Spherical Aberration in Nonhuman Primate Crystalline Lenses

Static and dynamic crystalline lens accommodation evaluated using quantitative 3-D OCT

The Optical Design of the Human Eye: a Critical Review

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