When we found out our 1-year-old needed glasses, we wanted to get the best ones the optometrist offered. We got these "Kid's" by "Safilo" and, well... they're definitely not designed for a 1-year-old. At least not one with access to stone tile flooring. The glass actually sticks out past the frames! And the "scratch-proof" coating? Cutting through that is literal child's play.
This protective frame snaps onto the front of these glasses and keeps the optics well clear of any flat-ish abrasive surfaces. I'm sure it's still no match for a gravel walkway or something like that, but at least with these you'll maybe go a day or two without a new scratch on your kid's glasses.
Printed in blue for picture, but I recommend transparent colors so it's less visually intrusive when wearing. Also, the tabs happen to be where my child's face sit away from the glasses frames. Your child may vary.
UPDATE: I added a newer version (mk6). I removed the inner tabs, because when I snapped those off the original version, it still worked just fine. The outer tabs are wider and a bit stronger, but the fit is also tighter than the original. Also, the newer version does not stick out over the nose bridge like the original. The first version took some light sanding on that part to make it more comfortable.
20% (doesn't matter that much)
I sanded a little notch where the bridge is, but it's not completely necessary.