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.

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The composite β-CS/HPa (30/70) as biodegradable bone substitute that not only enhance bone generation but also accelerate the formation of Haversian system. We used the composite in a powder form and examined its suitability as artificial bone graft; yet the mechanical properties have shown that 30/70 ratio of β-CS/HPa offer suitable mechanical strength to be employed as a solid-shaped implants.

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