Influence of power changes in single cut rigid contact lenses on tear pump efficiency
Differences between corneal oxygen uptake rates measured after 5 min of static (without blinking) and 5 min of dynamic (with blinking once every 5 s) non-gas permeable (polymethyl methacrylate) contact lens wear, referenced to the oxygen uptake rates of the normal open eye, were used as indications of tear pump efficiencies associated with each of seven contact lens back vertex powers (-9.00 to +9.00 D, in 3.00 D steps). Measurements were made in vivo on six human corneas showing with-the-rule (0.25 to 0.87 D) toricity. Lens overall diameter was 8.8 mm, optic zone diameter was 7.4 mm, and base curve radius was fitted "on K." Lens center thickness was 0.14 mm for all minus-powered lenses, and 0.19, 0.26, 0.34, and 0.41 mm for the plano, +3.00, +6.00, and +9.00 D lenses, respectively, maintaining an edge thickness of 0.11 mm. Under both static and dynamic wearing conditions, no significant differences were found among the corneal oxygen uptake rates associated with the various contact lens back vertex powers; however, the difference between the static and dynamic condition data, an indication of tear pump efficiency, was greatest for the -3.00 D lens. The difference values associated with the +9.00 and +6.00 D lenses were significantly lower than those associated with the minus power lenses.
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|Item Type:||Journal Article|
|Keywords:||Contact Lenses, Tears/, metabolism, Adult, Blinking, Comparative Study, Cornea/metabolism, Female, Humans, Male, Methylmethacrylate, Methylmethacrylates, Middle Aged, Orthoptics, Oxygen Consumption/physiology|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health|
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 1992 American Academy of Optometry|
|Copyright Statement:||Reproduced in accordance with the copyright policy of the publisher.|
|Deposited On:||13 Jul 2006|
|Last Modified:||09 Jun 2010 22:29|
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