Age-dependent variation of the gradient index profile in human crystalline lenses

Castro, Alberto de; Siedlecki, Damian; Borja, D.; Uhlhorn, Stephen; Parel, Jean Marie; Manns, Fabrice; Marcos, Susana

doi:10.1080/09500340.2011.565888

Cited by 38 publications

(44 citation statements)

References 31 publications

(45 reference statements)

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“…Different nondestructive methods have been proposed to estimate the lens GRIN distribution in vitro, including integral inversion methods, [17][18][19][20][21] optimization methods, 9,[22][23][24][25] or densitometrybased methods. 14,26,27 A recent optimization technique using optical path differences measured with an OCT as input data 28,29 has shown similar reconstruction accuracy to ray tracing optimization-based techniques. 30 The OCT high resolution and data acquisition speed makes it very suitable to investigate the changes of the GRIN with accommodation.…”

Section: Resultsmentioning

confidence: 99%

“…Several studies reveal changes of the GRIN in human crystalline lenses with age, with a progressive flattening of the GRIN profile in older lenses, 14,25,26,29 likely associated to age-related changes of the lens spherical aberration with age. We have recently shown that the presence of the GRIN plays a critical role in the negative spherical aberration of the isolated porcine, 28,31 Observations of the shift of spherical aberration in isolated porcine lens from negative values in virgin lenses to positive values after lens refilling with a homogeneous refractive index polymer also point to a fundamental role of the GRIN in the crystalline lens optical properties.…”

Section: Resultsmentioning

confidence: 99%

“…28,29 The height of the distorted surfaces in the OCT image is a recording of the optical path traveled by the light. A search algorithm was used to calculate the GRIN distribution that best matched the optical path accumulated by the rays passing through the lens and the back focal length measured.…”

Section: Grin Reconstructionmentioning

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: Resultsmentioning

confidence: 99%

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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“…All OCT images were processed to obtain the shape of the lens surfaces and the surface of the cuvette, using algorithms described in detail in previous publications [6]. We aligned the anterior and posterior surfaces using the astigmatism vector of the cuvette segmented surface.…”

Section: Lens Orientationmentioning

confidence: 99%

“…With aging, the human lens becomes thicker, relatively steeper, and looses the ability to accommodate [1][2][3]. In addition, the crystalline lens shows a gradient refractive index (GRIN) distribution, which also changes with age [4][5][6][7][8]. Recent work has shown that in human [9], as well as monkey [10] and porcine lenses [4], both the lens shape and the GRIN play a role in the negative spherical aberration of the lens.…”

Section: Introductionmentioning

confidence: 99%

OCT 3-D surface topography of isolated human crystalline lenses

Sun

Birkenfeld

Castro

et al. 2014

Biomed. Opt. Express

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Quantitative 3-D Optical Coherence Tomography was used to measure surface topography of 36 isolated human lenses, and to evaluate the relationship between anterior and posterior lens surface shape and their changes with age. All lens surfaces were fitted to 6th order Zernike polynomials. Astigmatism was the predominant surface aberration in anterior and posterior lens surfaces (accounting for ~55% and ~63% of the variance respectively), followed by spherical terms, coma, trefoil and tetrafoil. The amount of anterior and posterior surface astigmatism did not vary significantly with age. The relative angle between anterior and posterior surface astigmatism axes was on average 36.5 deg, tended to decrease with age, and was >45 deg in 36.1% lenses. The anterior surface RMS spherical term, RMS coma and 3rd order RMS decreased significantly with age. In general, there was a statistically significant correlation between the 3rd and 4th order terms of the anterior and posterior surfaces. Understanding the coordination of anterior and posterior lens surface geometries and their topographical changes with age sheds light into the role of the lens in the optical properties of the eye and the lens aging mechanism.

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Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism

et al. 2013

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The optical properties of the crystalline lens are determined by its shape and refractive index distribution. However, to date, those properties have not been measured together in the same lens, and therefore their relative contributions to optical aberrations are not fully understood. The shape, the optical path difference, and the focal length of ten porcine lenses (age around 6 months) were measured in vitro using Optical Coherence Tomography and laser ray tracing. The 3D Gradient Refractive Index distribution (GRIN) was reconstructed by means of an optimization method based on genetic algorithms. The optimization method searched for the parameters of a 4-variable GRIN model that best fits the distorted posterior surface of the lens in 18 different meridians. Spherical aberration and astigmatism of the lenses were estimated using computational ray tracing, with the reconstructed GRIN lens and an equivalent homogeneous refractive index. For all lenses the posterior radius of curvature was systematically steeper than the anterior one, and the conic constant of both the anterior and posterior positive surfaces was positive. In average, the measured focal length increased with increasing pupil diameter, consistent with a crystalline lens negative spherical aberration. The refractive index of nucleus and surface was reconstructed to an average value of 1.427 and 1.364, respectively, for 633 nm. The results of the GRIN reconstruction showed a wide distribution of the index in all lens samples. The GRIN shifted spherical aberration towards negative values when compared to a homogeneous index. A negative spherical aberration with GRIN was found in 8 of the 10 lenses. The presence of GRIN also produced a decrease in the total amount of lens astigmatism in most lenses, while the axis of astigmatism was only little influenced by the presence of GRIN. To our knowledge, this study is the first systematic experimental study of the relative contribution of geometry and GRIN to the aberrations in a mammal lens.

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Age-dependent variation of the gradient index profile in human crystalline lenses

Cited by 38 publications

References 31 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

OCT 3-D surface topography of isolated human crystalline lenses

Contribution of the gradient refractive index and shape to the crystalline lens spherical aberration and astigmatism

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