City Research Online

Abstract

The history of cataract and its treatment is outlined. The number of cataract extractions per year in the United Kingdom is given with a discussion on the need for a good post-cataract (aphakic) optical correction. The unwanted optical effects of high plus spectacle lenses are contrasted with these optical effects in contact or intra-ocular lens form.

The handling problem of daily worn contact lenses by the (mostly) elderly population and the surgical problems of intra-ocular lens implants are discussed with the advantages of the good optical correction by the soft lens coupled with the ability for rapid removal should clinical problems arise.

The areas of measurement studied in this thesis are the temperature difference between the room and the eye, and the effect of these differences on the intensive properties of water content, refractive index, and permeability of soft lens materials and the extensive properties or dimensional changes in back and front radii of high plus lenses.

Another area of measurement studied is the effect on back vertex power of high plus lenses on 'bending* from the form of the lens in the bottle to the shape of the lens on the eye.

The last area of measurement recorded is the oxygen tension at the anterior corneal surface of the aphakic and phakic eye.

Visual acuity standards are given with respect to spectacles and various back radii fittings of high plus soft lensesand the hypothesis given that high plus soft lenses should be fitted with a particular back radius to achieve the highest standard of visual acuity.

Finally, this thesis gives a new method of fitting high plus soft lensesusing the traditional high plus PMMA fitting set as a diagnostic aid. The transposition of these PMMA parameters to the parameters of the soft lens on the eye and to the soft lens to be ordered from the manufacturers is given by taking into account the effects of heat and 'bending* on the parameters of high plus soft lenses. These calculations are summarised graphically.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine R Medicine > RE Ophthalmology
Departments:	School of Health & Medical Sciences > Optometry & Visual Sciences School of Health & Medical Sciences > School of Health & Medical Sciences Doctoral Theses Doctoral Theses

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