I was suprised to see how old this thread was. But relevant nonetheless.
My profession would dictate that PPE is a necessity & should be worn at all times. Unfortunately, complacency bites everyone & I often do not wear glasses while shooting rifles. I ALWAYS have my Oakley sunglasses stuck to my face or on the brim of my hat but there is a slight problem.
The size of my glasses coupled with the contour of my face allows my glasses to slide down just far enough to serously interfere with my ability to look through a scope. So I take them off.
Pistols, no prob, glasses always. One of my AR's? No issues as they are usually shot standing etc. Rifles, I am still working on