They will (actually may) keep the visor fog free depends on temp and helmet. My heated visor remains clear if I keep it plugged in 100% of the time from warm up but my *&^$ glasses still fog up and so does the retractable yellow glare shield. I end up running around with the front visor cracked open a 1/2 inch or so even at -30 so I can see
I second that, no... I've got a heated visor, and although I don't wear glasses, my helmet has internal sunglasses that drop down. I can only use those in very specific conditions, most of the time they fog up.
Heated visors don't actually give off any heat, they create just enough heat in the plastic shield to keep it from fogging.