I've worn glasses all my life and it's rarely ever a problem when cycling. However, I'm fortunate enough to be hyperopic with a near null defect in one eye. When it rains, the glasses are often handy to keep splatter out of the eyes. If the rain gets too heavy then I just take them off. Being hyperopic means that I don't suffer any degredation in my operating vision for cycling without them. I've never had a problem with humidity/heat/sweat except when the nosepads are really new. However, I am careful about the type of pads that I get. As for crashing, I usually specify titanium frames and plastic scratch resistant lenses.
I've worn glasses all my life and it's rarely ever a problem when cycling. However, I'm fortunate enough to be hyperopic with a near null defect in one eye. When it rains, the glasses are often handy to keep splatter out of the eyes. If the rain gets too heavy then I just take them off. Being hyperopic means that I don't suffer any degredation in my operating vision for cycling without them. I've never had a problem with humidity/heat/sweat except when the nosepads are really new. However, I am careful about the type of pads that I get. As for crashing, I usually specify titanium frames and plastic scratch resistant lenses.