Effects of coatings on the fracture resistance of ophthalmic lenses.
BACKGROUND
Scratch-resistant (SR) and anti-reflective (AR) coatings are commonly applied to plastic ophthalmic lenses. Fracture resistance is greatly affected by surface characteristics, and coatings may have a weakening effect. Static load testing is an efficient, quantifiable alternative to the drop ball test and has been suggested as useful for comparing lenses of a given material.


METHODS
An Instron static load tester was used to test the fracture resistance of 140 CR-39 lenses divided into 4 groups: uncoated, prepared for AR coating but not actually coated, AR coated, and factory SR coated.


RESULTS
Compared to the control uncoated group, AR coating reduced the required fracture energy by 63% and SR coating by 57%. Preparation for AR coating had no significant effect.


CONCLUSIONS
These results are at least qualitatively consistent with drop ball testing and have significant implications as new plastic materials are developed, made thinner, and variously coated.
Corzine
J C
JC
School of Optometry, University of California, Berkeley, USA.
Greer
R B
RB
Bruess
R D
RD
Lee
G K
GK
Scaief
A L
AL
D004867:Equipment Design; D004869:Equipment Safety; D005139:Eyeglasses; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods; D013499:Surface Properties