Controlling optical properties of sclera

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Abstract
Transscleral laser microsurgery has gained wide acceptance recently. Many problems in this field are due to laser beam decay in an optically nonhomogeneous sciera. The sciera light transmission in defined by scattering processes on its fibers. Because of high density in the arrangement of sciera fibers, the phenomena of interferential interaction between scattered radiation and multiple scattering are essential. Our paper is aimed at the theoretical and experimental validation of light scattering decrease on collagen fibers by substituting the sciera base substance with substance exhibiting higher refraction index. As a model of sciera, system of long dielectric cylinders was chosen, which were surrounded by isotropic base substance with lower refraction index. The fibril diameters are varied from 10 to 100 nm. The indexes of refraction for the fibrils and embedding substance differ appreciably from each other and are equal2, respectively) to 1,47 and 1.345. The thickness of sciera is I mm. The statistic characteristics of spatial arrangement of fiber centers were described at an approximation of exduded volume. The scattering amplitude function for a single cylinder was calculated using Mie theory. Under calculation it was assumed that the axes of all the fibers are parallel to the sciera surface and their orientation in this plane is random. Two complex coefficients for waves, polarized in parallel and normally to the fiber axes, were found by means of method describing the propagation of coherent waves through random systems. According to this approach, scattering medium is represented as homogeneous but a having new effective refraction index. The imaginary part of the index takes into account energy extinction due to scattering.

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