Refractive index degeneration in older lenses : a potential functional correlate to structural changes that underlie cataract formation

Bahrami, Mehdi, Hoshino, Masato, Pierscionek, Barbara, Yagi, Naoto, Regini, Justyn and Uesugi, Kentaro (2015) Refractive index degeneration in older lenses : a potential functional correlate to structural changes that underlie cataract formation. Experimental Eye Research, 140, pp. 19-27. ISSN (print) 00144-835

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A major structure/function relationship in the eye lens is that between the constituent proteins, the crystallins and the optical property of refractive index. Structural breakdown that leads to cataract has been investigated in a number of studies; the concomitant changes in the optics, namely increases in light attenuation have also been well documented. Specific changes in the refractive index gradient that cause such attenuation, however, are not well studied because previous methods of measuring refractive index require transparent samples. The X-ray Talbot interferometric method using synchrotron radiation allows for measurement of fine changes in refractive index through lenses with opacities. The findings of this study on older human lenses show disruptions to the refractive index gradient and in the refractive index contours. These disruptions are linked to location in the lens and occur in polar regions, along or close to the equatorial plane or in lamellar-like formations. The disruptions that are seen in the polar regions manifest branching formations that alter with progression through the lens with some similarity to lens sutures. This study shows how the refractive index gradient, which is needed to maintain image quality of the eye, may be disturbed and that this can occur in a number of distinct ways. These findings offer insight into functional changes to a major optical parameter in older lenses. Further studies are needed to elicit how these may be related to structural degenerations reported in the literature.

Item Type: Article
Additional Information: This work is supported by Fight for Sight (grant number 1319/1320) and beamtime grant from the SPring-8 synchrotron (grant numbers 2013A1651 and 2014A1710).
Uncontrolled Keywords: lens, human, cataract, refractive index, synchrotron, x-ray talbot interferometry
Research Area: Allied health professions and studies
Biological sciences
Faculty, School or Research Centre: Faculty of Science, Engineering and Computing (until 2017)
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Depositing User: Anna Englund
Date Deposited: 13 Oct 2015 10:51
Last Modified: 06 Sep 2019 08:57

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