Examination of the effect of the fibrous structure of a lens on the optical characteristics of the human eye: a computer-simulated model

Abstract

We introduce a model of the human eye for which we take into consideration the laminated nature of lens fibers. The thickness of each lamina is 5.6 µm; thus the lens comprises 300 eccentric lenses of minute dimensions. The index gradient of the lens is such that the index of refraction increases exponentially from the lens core to its peripheral zone. A vector ray-tracing technique is employed to study the optical haracteristics of the system. Both paraxial and marginal rays are simulated, and the angles of incidence vary from 0° to ±20°. Special attention is given to the meridional caustic surfaces as well as the wave-front distortion of the refracted rays. A quasi-Newton optimization technique is employed to obtain the best parameters for the system. A computer modeling program, written in FORTRAN 77, is used to simulate a ray's refraction through the multisurfaces of the eye. The results show full agreement with previous data and that the cornea is responsible for eliminating possible spherical aberration of the system.

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.…”

“…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

“…Smith [9] propuso describir las superficies isoíndices con funciones bielípticas. Se ha estudiado la posibilidad de describir el GRIN utilizando varias capas de índice de refracción constante en vez de una distribución de gradiente de índice [10][11][12][13]. En la zona paraxial se ha modelado matemáticamente la óptica, la potencia axial y los puntos cardinales del cristalino [14][15][16].…”

“…En cristalinos con simetría esférica se ha reconstruido el GRIN usando como datos experimentales la dirección de los rayos refractados [39] y también datos de Tomografía de Coherencia Óptica (OCT) [40]. En cristalinos no esféricos, como es el caso del humano, la elección de un modelo muy complicado puede hacer que el problema tenga múltiples soluciones posibles y por tanto resultados difíciles de interpretar [12,13]. Sin embargo, usando un modelo de una sola variable se han observado [41] ligeras diferencias entre el GRIN de cristalinos de distintos grupos de edad.…”

Complete algorithm for the calculation light patterns inside the ocular media

“…Numerical analysis and simulation of light propagation through the human eye and interaction with its different optical surfaces have become a fundamental tool in understanding the optical performance of the human eye [1][2][3][4][5][6]. Applications derived from fundamental investigation of optical systems may have a real impact on the final quality of the life of subjects affected by severe refractive dysfunction.…”