The gradient index lens of the eye: an opto-biological synchrony

Pierscionek, Barbara K. and Regini, Justyn W. (2012) The gradient index lens of the eye: an opto-biological synchrony. Progress in Retinal and Eye Research, 31(4), pp. 332-349. ISSN (print) 1350-9462

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Abstract

The refractive power of a lens is determined largely by its surface curvatures and the refractive index of its medium. These properties can also be used to control the sharpness of focus and hence the image quality. One of the most effective ways of doing this is with a gradient index. Eye lenses of all species, thus far, measured, are gradient index (GRIN) structures. The index gradation is one that increases from the periphery of the lens to its centre but the steepness of the gradient and the magnitudes of the refractive index vary so that the optics of the lens accords with visual demands. The structural proteins, the crystallins, which create the index gradient, also vary from species to species, in type and relative distribution across the tissue. The crystallin classes do not contribute equally to the refractive index, and this may be related to their structure and amino acid content. This article compares GRIN forms in eye lenses of varying species, the relevance of these forms to visual requirements, and the relationship between refractive index and the structural proteins. Consideration is given to the dynamics of a living lens, potential variations in the GRIN form with physiological changes and the possible link between discontinuities in the gradient and growth. Finally, the property of birefringence and the characteristic polarisation patterns seen in highly ordered crystals that have also been observed in specially prepared eye lenses are described and discussed.

Item Type: Article
Additional Information: This work was supported by the National Health and Medical Research Council; the Engineering and Physical Sciences Research Council and Essilor International.
Uncontrolled Keywords: gradient refractive index, eye lens, crystallins, specific refractive increment, dispersion, image quality, birefringence, human crystalline lens, age-related-changes, african cichlid fish, longitudinal chromatic aberration, optical coherence tomography, surface refractive-index, resonance-imaging mri, gamma-crystallin, bovine lens, spherical-aberration
Research Area: Physics
Pre-clinical and human biological sciences
Faculty, School or Research Centre: Faculty of Science, Engineering and Computing
Related URLs:
Depositing User: Nikki Phillips
Date Deposited: 22 Mar 2012 12:26
Last Modified: 05 Dec 2012 11:17
URI: http://eprints.kingston.ac.uk/id/eprint/22580

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