Statistical procedures for impact resistance testing at increased drop-ball heights.
OBJECTIVE
Impact resistance testing of prescription eyewear and nonprescription sunglasses is normally performed at a drop-ball height of 50 in (1.27 m). This paper presents a statistics-based testing method that uses increased drop-ball heights.


METHODS
Impact resistance values for glass and plastic lens materials were obtained from the available literature. These values were used to determine the characteristics of marginal quality and high quality batches of lenses. Impact resistance testing procedures were then developed that accepted these batches at low and high probabilities, respectively.


RESULTS
A large number of test parameter combinations met the requirements of the impact resistance testing procedure. In general, increasing the drop-ball test height decreased the sample size needed to demonstrate that a batch of lenses was impact resistant.


CONCLUSIONS
Impact resistance testing at increased drop-ball heights is an alternative to traditional statistics-based testing procedures. Sample size can be smaller, and equipment is relatively inexpensive and readily available.
College of Optometry, University of Houston, Texas, USA.
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Stephens
D005135:Eye Protective Devices; D005139:Eyeglasses; D008422:Materials Testing; D055656:Prescriptions; D013223:Statistics as Topic; D013472:Sunlight; D014481:United States; D014486:United States Food and Drug Administration