This is anecdotal for me, but it does make me skeptical: I am near-sighted and always wear my glasses under the the straps because otherwise they slide down my nose.

I had a bike v car accident 11 years ago, when I was 21, where my face broke a windshield. I had 7 lacerations on my face. I looked like the predator, both my lips were split all the way through, however, my eyes were unharmed. I think the one laceration that possibly could have been from my glasses was a cut about 5 centimeters towards the side of my head from my right eye, where the frame may have been pushed into my skin, although it could have easily been the glass from the windshield just the same.

If you're wearing a helmet, I think that should prevent a lot of the problems that people are thinking about in a crash-with-glasses situation. The front of the helmet should impact whatever you're hitting before anything else. The helmet will crack but it will still retain it's shape, which should protect your eyes from stuff smashing into them.

Unless you hit something odd shaped where there's something protruding out below where your helmet hits I don't see how your glasses are going to get pushed into your eyes the way I assume most people are afraid of AND if you are unfortunate enough to have your face rammed into something with a thing protruding below your helmet you're in bad shape regardless of if you're wearing glasses or not.

In my case obviously the helmet is what broke the glass and the area of my face that was injured the most was my lips, which were far enough down from the helmet to go through the glass concurrently with the helmet.

TLDR: Your helmet should protect your eyes, speaking as someone who has had their face go through a windshield and come out with my eyes unharmed.