Hey Frank
If you go by that rule then you should not wear shades with glass lenses anywhere. Lots of hazards you know, tree branches, birds, golf balls, tennis balls, car doors, a backhander from the wife, hell you could take a hit at anytime night or day!
Seriously though dood I dropped my serri's onto the concrete footpath (and the lense hit first), I cringed at the time but so much as a chip. God speed my friend and look out for the back end of that flap on the 172!