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Wide-field anterior ocular surface morphometrics

Turner, Jennifer 2011. Wide-field anterior ocular surface morphometrics. PhD Thesis, Cardiff University.
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Abstract

The current understanding of anterior eye shape in humans is limited due to available technology and its accessibility. Accurate curvature metrics of specific areas of the peripheral cornea, corneo-limbal junction and anterior sclera have remained obscured by the limits of the palpebral aperture, since the upper and lower eyelids cover most of the vertical aspect. This thesis starts by comparing the ‘gold standard’ keratometry measurements to commonly used topographic systems. Keratometric analogues were found to be significantly different and in addition provided spurious vertical anterior ocular surface (AOS) profiles. These findings revealed a need to establish an accurate model. Magnetic resonance imaging (MRI) potentially offers the best opportunity to image the entire AOS structure. However, preliminary studies in this thesis demonstrated that the use of a 3-Tesla MRI scanner was unable to obtain sufficiently resolute data to meet requirements. As an alternative, ocular impression taking techniques were adopted during the remainder of this work to acquire the AOS data. Eye casts from impression moulds were scanned using active laser triangulation and virtual 3-dimensional surfaces rendered. Further investigations defined the most suitable material for impression taking and the amount of deformation of the AOS caused by the procedure. The ocular impression casting and scanning process was examined for accuracy and reliability. This protocol was used to sample a population of normal white European eyes in order to establish a database and define wide-field AOS variability. Volumetric and 2-dimensional topographic profiles were extracted from the digital 3-dimensional representation obtained, allowing for the analysis of point-to-point curvature differences. For the first time, the entire AOS shape has been defined with known accuracy. In addition, effects of myopic refractive error and gender are presented. This data is of potential importance to ophthalmic surgeons, ocularists, contact lens practitioners, vision scientists and researchers, in the form of a digital archive of normal white European wide-field AOS topography as a reference source.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Optometry and Vision Sciences
Subjects: R Medicine > RE Ophthalmology
Uncontrolled Keywords: Anterior ocular surface; Wide-field topography; Ocular impression; Axial radius of curvature; Cornea; Sclera; Morphometrics; Eye shape.
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 03:44
URI: http://orca.cf.ac.uk/id/eprint/25655

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