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Structural changes in the eye lens during accommodation

Al-Atawi, Saleha 2019. Structural changes in the eye lens during accommodation. PhD Thesis, Cardiff University.
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Abstract

Aim: The main aim of this thesis was to investigate the changes in the lens crystallin molecular spacing and ordering, the lens suture confluence area, and the lens fibre widths, during the accommodation. Methods: The molecular spacing and ordering of crystallin proteins were analysed using small angle X-ray scattering (SAXS) in Atlantic salmon, European ‎squid and porcine lenses, and additionally in stretched and unstretched porcine lenses. Confocal microscopy was used to image anterior and posterior lenses to quantify changes in the lens suture confluence areas and lens fibre widths. In serial cryosections of porcine lenses, accommodative changes in lens fibre widths were analysed in both the nucleus and cortex. Results: The molecular spacing of crystallins within the porcine lens nucleus was significantly less than in the Atlantic salmon and European ‎squid lenses. As a case in point, the Bragg spacing in the porcine nucleus area, at 1mm along the horizontal meridian, ‎decreased from 18.9 ± 0.3 nm to 15.9 ±0.3 nm.‎ Furthermore, significant accommodative changes in the average spacing between crystallin proteins in all vertical and horizontal meridians (p < 0.05) were determined. For instance, at the 1 mm vertical meridian, Bragg spacing in an unstretched lens increased from 16.6 ± 0.6 nm to 20.9 ± 2.8 nm in a stretched lens. The suture confluence area also changed following stretch at some depths. A significant increase in lens fibre widths in stretched lenses was observed in the nucleus (43.3 ± 10.2m versus 47.1 ± 8.6m, p = 0.001), the anterior cortex (67.4 ± 16.8m versus 72.9 ± 17.8m, p = 0.000), and the equatorial cortex (90.5 ± 11.2m versus 96.5 ± 11.9m, p = 0.002). However, a significant reduction in the posterior cortical lens fibre widths (69.3 ± 12.4m versus 59.6 ± 9.4m, p = 0.0000) in stretched lenses. Conclusion: The accommodation, as characterised in a porcine model, involves significant structural changes within lens crystallins and fibre widths. To the researcher’s knowledge, the novel data is provided herein. This study contributes to future research in this area by offering enhanced fixation protocols that preserve lens shape, in both accommodated and unaccommodated state, particularly important for 2D SAXS grid scans and microscopy-based analyses.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: Lens; Accommodation; Ultrastructure; SAXS
Date of First Compliant Deposit: 15 January 2020
Last Modified: 16 Jan 2020 11:35
URI: http://orca.cf.ac.uk/id/eprint/128419

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