Single dispersive gradient-index profile for the aging human lens

Abstract

We provide a single gradient-index (GRIN) profile for the crystalline lens in an updated age-dependent emmetropic-eye model. The parameters defining the GRIN profile include their variation with age and the dispersion of the refractive index in order to account for the increase in the positive-wave spherical aberration, for the constant chromatic difference in the refraction of the human eye, as well as for the decrease in the retinal-image quality with aging. In accounting for these ocular properties, the results show that first, the value of the dispersion parameters are invariant with age. Second, those parameters defining the distribution of the lens index cause the lens-center-index value to decrease slightly, and its position along the lens axis changes with age. Furthermore, these findings are in agreement with the lens paradox.

The Optical Design of the Human Eye: a Critical Review

“…This fact was already studied by Gullstrand. 4 It is worth saying that GRIN data on human lenses are even more scarce, [62][63][64][65] whereas much more modeling work 13,16,19,20,[27][28][29]66,67 has been done. There is a general consensus that the refractive index of the lens seems to increase monotonically from the surface to the center and also that the GRIN structure increases the refractive power of the lens.…”

“…-Paraxial 4,6 versus finite optical performance 7,9,10 (optical and image quality), -Homogeneous 7,9 versus gradient index (GRIN) lens 5,11-13 -On-axis 3,5 versus wide angle 11,14,15 -Unaccommodated 9 versus accommodative 7,16,17 -Age-independent 4 versus aging [18][19][20] -Generic 4,21 versus custom or personalized. 22,23 Other relevant aspects, such as intraocular scattering, have been incorporated only in a few models.…”

“…In fact, most of the crystalline's models consider the GRIN structure within the lens. 5,11,13,[16][17][18]20,[25][26][27][28][29] Such variety of models reflects the fact that all models are incomplete, since the real human eye contains both cornea and lens (anatomical), works with polychromatic light, it is known to have a limited optical performance (aberrations), it has a very wide visual field, it uses accommodation to focus near objects and it evolves throughout life span. Above all, any model must account for short-term (accommodation) and long-term (ageing) changes.…”

Reconstruction of the gradient refractive index of the crystalline lens with optimization methods

“…Goncharov y Dainty [24] propusieron tres modelos de distinto número de variables para simular la óptica del cristalino. Díaz [25,26] estudió la posibilidad de usar funciones sinusoidales y un decrecimiento parabólico del índice de refracción en eje. Manns [27] propuso un modelo simple asumiendo que la caída de índice de refracción desde el núcleo hacia la superfice se puede modelar usando una ecuación potencial.…”

Polymeric nanolayered gradient refractive index lenses: technology review and introduction of spherical gradient refractive index ball lenses

“…Without GRIN optics, spherically curved homogenous lenses could still focus light and offer large fields of view, however, they would exhibit significant spherical aberrations and focused light would not intersect at one point along the lens's optical axis, causing image blur. [1][2][3] By contrast, air-dwelling creatures, [9][10][11][12] such as the lion, cow, rat, and human, utilize GRIN lenses to correct for significantly larger geometric aberrations stemming from a larger difference in environment (air n ¼ 1.0) to lens material (n ¼ 1.33 to 1.43) refractive index as well as contributions from aspheric-shaped lenses (Table 1). A bi-product of nature's incorporation of GRIN into eye lens optics has resulted in most biological imaging systems containing a low, typically one to three, number of lenses, which minimizes the size necessary for an organism's eyes to exhibit a powerful accommodating image system.…”