Prescription compliance in ophthalmic lenses

Autor: Brian B Cheng, Thao P T Ngo, Gloria S‐c Yuen, B Ralph Chou, Stephen J. Dain
Rok vydání: 2011
Předmět:
Zdroj: Clinical and Experimental Optometry. 94:341-347
ISSN: 1444-0938
0816-4622
Popis: Purpose: Tolerances required for ophthalmic lenses are set down in national and international standards. It appears that the compliance of manufactured lenses has not been reported previously. Assembling a statistical quantity of lenses of a single prescription is usually an expensive process. It was, secondary to a lens impact study, possible to assemble a large number of plano lenses. In the assessment of the fracture velocity of lenses approximately 20 plano lenses of each material and thickness are required. Prior to using lenses for the impact study, they were checked for prescription. The results of the prescription measurements are reported here and the results of the impact study are reported in a separate paper. Methods: Using an automated focimeter, 679 plano lenses in stock thickness, typical occupational eye protector thickness and up to 3.5 mm thick were measured. There were 21 combinations of material/thickness/coating from seven suppliers. The power was evaluated against Australian Standard 2228.1-1992, as the lenses were supplied in Australia. The permitted tolerances are ±0.09 D sphere and ±0.06 D cylinder. Results: When assessed for material/thickness/coating combination, failure rates varied from
Databáze: OpenAIRE
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