Impact resistance and prescription compliance with AS/NZS 1337.6:2010

Background: Australian/New Zealand Standard 1337.6 deals with prescription eye protection and has been in place since 2007. There have been many standards marking licences granted since then. The issue of the worst-case situations for assessment in a certification scheme, in particular -1.50m(-1) lenses, has been the subject of discussion in Standards Australia/Standards New Zealand Committee SF-006. Given that a body of data from testing exists, this was explored to advise the Committee. Methods: Data from testing 40 sets of prescription eye protectors were analysed retrospectively for compliance with the impact and refractive power requirements in 2010-11. The testing had been carried out according to the methods of AS/NZS 1337.6:2007 under the terms and conditions of the accreditation of the Optics & Radiometry Laboratory by the National Association of Testing Authorities. Results: No eye protector failed the low-impact resistance test. Failure rates of 1.6 per cent (two of the 40 sets) to the medium impact test and 1.6 per cent (three of the sets) to the medium impact test in the elevated temperature stability test were seen. These are too small for useful statistical analysis. Only -1.50m(-1) lenses were in all failing sets and these lenses were over-represented in the failures and borderlines, especially compared with the +1.50D lenses. Failures in prismatic power were equally distributed over all prescriptions. This over-representation of -1.50m(-1) lenses was not related to the ocular/lens material or to the company manufacturing the eye protectors. Conclusions: The proposal is made that glazing lenses tightly to ensure they are retained in the frame on impact may result in unwanted refractive power in those lenses most prone to flex. These data support the proposal that -1.50m(-1) lenses should form part of a worst-case testing regime in a certification scheme.