Shatter resistance of spectacle lenses.
OBJECTIVE
To evaluate the relative strength and shatter resistance of spectacle lenses currently used in sunglasses and dress, sports, and industrial eyewear.


METHODS
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).


METHODS
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.
Vinger
P F
PF
Tufts Medical School, Medford, Mass, USA.
Parver
L
L
Alfaro
D V
DV
Woods
T
T
Abrams
B S
BS
D005135:Eye Protective Devices / Q000592:standards; D005139:Eyeglasses / Q000592:standards; D005898:Glass; D006801:Humans; D008422:Materials Testing; D010969:Plastics; D011076:Polycarboxylate Cement; D012449:Safety
D010969:Plastics; D011076:Polycarboxylate Cement; C005506:polycarbonate