Non-conventional Types of Varifocal Spectacle Lens


The condition known as presbyopia is a normal physiological process, which begins to cause problems with near vision in middle-age. Unfortunately, although there are many varifocal lenses available which give some form of continuously variable vision, as in the pre-presbyopic eye, all current designs are compromise approaches to the problem, Sullivan and Fowler (1989) reporting a 12.5 % failure rate with one type. The aim therefore of this project was to investigate three different approaches to the one normally used, these being liquid crystal lenses, gradient index optics, and deformable lenses. In the case of liquid crystals, an extensive literature survey was carried out, and a theoretical analysis of performance. In the case of gradient index optics and deformable lenses, a literature review was made and practical measurements were carried out, on experimental lenses constructed in the laboratory. The liquid crystal lenses would seem to offer the best prospects for the long term, although there are severe difficulties to be overcome before they can be mass- produced. Gradient index lenses still require the development of a suitably stable lens material, and even then would not seem to offer many advantages over the existing lenses. Deformable lenses can be readily constructed, but are difficult to mass- produce, and suffer from leakage of the hydraulic control system

Divisions: College of Health & Life Sciences > School of Optometry > Optometry
Additional Information: Copyright © Evangelos Pateras, 1989. Evangelos Pateras asserts their moral right to be identified as the author of this thesis. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without appropriate permission or acknowledgement. If you have discovered material in Aston Publications Explorer which is unlawful e.g. breaches copyright, (either yours or that of a third party) or any other law, including but not limited to those relating to patent, trademark, confidentiality, data protection, obscenity, defamation, libel, then please read our Takedown Policy and contact the service immediately.
Institution: Aston University
Uncontrolled Keywords: varifocal,spectacle lens,gradient index,liquid crystal lenses,deformable lenses
Last Modified: 28 Jun 2024 07:32
Date Deposited: 21 Feb 2011 11:30
Completed Date: 1989-11
Authors: Pateras, Evangelos

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