Elsevier

Vision Research

Volume 41, Issue 8, April 2001, Pages 973-979
Vision Research

Gradient refractive index of the crystalline lens of the Black Oreo Dory (Allocyttus Niger): comparison of magnetic resonance imaging (MRI) and laser ray-trace methods

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Abstract

The gradient refractive index of the crystalline lens in the Black Oreo Dory (Allocyttus Niger) was determined using two methods; an optimisation program based on finite ray-tracing and the path of laser beams through the lens, and magnetic resonance imaging (MRI) and the linear relationship between refractive index and nuclear transverse relaxation rates. The methods showed good agreement in the cortical zone of the lens, but the lack of free water in the core of the lens made MRI measurement impossible in this region. The laser-optimisation method gave mean values of 1.368 and 1.543 for the surface and core refractive indices respectively, with a radial distribution for the gradient refractive index given by n(r)=1.543−0.121r2−0.033r4−0.021r6.

Keywords

Refractive index distribution
Fish lens
Lens models
Magnetic resonance imaging

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