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Shatter Resistance of Spectacle Lenses
Paul F. Vinger, MD;
Leonard Parver, MD;
D. Virgil Alfaro III, MD;
Thomas Woods;
Bernard S. Abrams, OD
JAMA. 1997;277(2):142-144.
Abstract
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Objective.
—To evaluate the relative strength and shatter resistance of spectacle lenses currently used in sunglasses and dress, sports, and industrial eyewear.
Design.
—Seven lenses that met the US American National Standards Institute (ANSI) Z80 standards for dress glasses (made of high-index plastic, allyl resin plastic, heat tempered glass, chemically tempered glass, and polycarbonate, and with center thickness ranging from 1 mm to 2.2 mm) and 4 lenses that met ANSI Z87 standards for industrial safety eyewear (allyl resin plastic, heat-tempered glass, chemically tempered glass, and polycarbonate, all with 3.0-mm center thickness) were tested for impact resistance to 5 projectiles (air gun pellets, golf balls, tennis balls, lacrosse balls, and baseballs).
Main Outcome Measures.
—Impact energy required to shatter spectacle lenses.
Results.
—Based on 348 lens impacts, dress and industrial lenses made from glass, allyl resin plastic, and high-index plastic shattered at impact energies less than those expected to be encountered from the test projectiles during their routine use. Polycarbonate lenses demonstrated resistance to impact for all tested projectiles exceeding the impact potential expected during routine use.
Conclusions.
—Under the test conditions of this study, polycarbonate lenses demonstrated greater impact resistance than other commonly used spectacle lenses that conform to prevailing eyewear standards. These findings suggest that current ANSI Z80 and ANSI Z87 standards should be reevaluated.
Author Affiliations
From Tufts Medical School, Medford, Mass (Dr Vinger; the Wilmer Eye Institute, Johns Hopkins University, Bethesda, Md (Dr Parver); the Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, Md (Dr Alfaro; New York City Technical College, City University of New York (Mr Woods); and The Ohio State University, Columbus (Dr Abrams).
Footnotes
None of the authors has a financial interest in any of the products discussed.
Reprints: Paul F. Vinger, MD, 297 Heath's Bridge Rd, Concord, MA 01742.
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