Equivalent power of the crystalline lens of the human eye: comparison of methods of calculation.
We present four methods, with different levels of sophistication and precision, for calculating the refractive power of the ocular lens from its optical structure. The first method uses finite ray tracing but simulates a paraxial ray by using small ray heights. The second method involves a recursive paraxial ray-tracing procedure. The other two methods do not depend on any ray-tracing procedure but use much simpler, approximate equations. In the third method the ray height is assumed not to change within the lens, and in the fourth method the ray path is assumed to be parabolic. The fourth method, but not the third method, can separately calculate the power of the surfaces and the gradient-index lens bulk, which are then used in the three-lens equation to calculate the power of the lens as a whole.
Smith
G
G
Department of Optometry, University of Melbourne, Parkville, Victoria, Australia.
Atchison
D A
DA
D006801:Humans; D007908:Lens, Crystalline / Q000502:physiology*; D008954:Models, Biological; D012029:Refraction, Ocular / Q000502:physiology*