RST Engineering wrote:

As you can imagine, after 30 years of fighting it out with the toothpaste
and razor, tumbling about as the airplane moves smartly through turbulence,
those glasses are scratched and pretty snotty looking.

If the lenses are plastic, the scratches can be polished out by any optical
house. Cheaper than new lenses.

George Patterson
The desire for safety stands against every great and noble enterprise.