From personal experience, not sure if it means much, but I find that skating without glasses is fine (and I'm legally blind without them on). I can see enough to avoid people and I don't have to worry about glasses falling off during jumps. The single scariest thing that could happen in a double loop is for your glasses to fall off halfway, and if my glasses aren't staying on, I'm taking them off.
For a competitive skater, maybe they could get used to not seeing their surroundings clearly, because after all the most you would need is an awareness of where you are in the rink relative to others and the boundaries of the rink (I might be mistaken).
For a competitive skater, maybe they could get used to not seeing their surroundings clearly, because after all the most you would need is an awareness of where you are in the rink relative to others and the boundaries of the rink (I might be mistaken).