Prescription safety eyewear: impact studies of lens and frame failure.
OBJECTIVE
To determine if a plano lens could be the test lens for all prescription (Rx) lenses and to investigate why Rx lenses pop out of safety eyewear.


METHODS
Plano and Rx polycarbonate lenses (n = 641) with varying thickness and edge geometry, mounted on steel lens holders, and Rx safety eyewear (n = 128) placed on headforms were impacted with test objects of varying diameter and hardness. Impacts were studied with 500 to 2,000 frames-per-second motion analysis.


RESULTS
Plano lenses were at least, or more, prone to failure (dislodgment, perforation, shatter, or crack) than -3.00 or +3.00 lenses of the same minimum thickness. More than 40% of safety frames with removable lenses broke or had lenses pop out when impacted with energies expected in industry and sports.


CONCLUSIONS
Plano lenses can be used as the test lenses for all Rx lenses made of the same material with the same minimal thickness. The ANSI Z87.1-1989 industrial standard for Rx eyewear is inadequate for sports or other activities with high-impact potential. The best lens-retention system has, as a component, a frame with a bevel perpendicular to a frontal impact force.
Vinger
P F
PF
Tufts University School of Medicine, Medford, Massachusetts, USA.
Woods
T A
TA
D004389:Durable Medical Equipment / Q000592:standards*; D004868:Equipment Failure; D004869:Equipment Safety; D005131:Eye Injuries / Q000209:etiology / Q000517:prevention & control; D005139:Eyeglasses; D006801:Humans; D055656:Prescriptions; D012030:Refractive Errors / Q000534:rehabilitation; D012449:Safety; D013718:Tensile Strength