As you can see. There are 9 parts for a pear of glasses.They are Rims,End pieces,Bridge,Hinges,Lenses,Screws,Nose pads,Pad arms and Temples.Each part of them needs to work together. 

For example,the Rims hold the Lenses.

However,each part will worn.We nee to know each part’s ability.

The ISO-12870 Spectacle Frame Tester can help us know what’s the frame’s ability.

The measurement frame has a certain lens retention ability, ensuring that the frame can be safely worn for 2 years or more, preventing the lens from falling off due to a slight impact, affecting the wearing effect.

This Spectacle Frame Tester with a electronic display and automatic timing device,and needs temperature 23 ± 2 ℃, relative humidity 60 ± 2% for the testing environment.

More information refer: https://www.labtesting-equipment.com/sale-12430109-spectacle-frame-tester-iso-12870-spectacle-frame-bridge-deformation-tester.html