Some cars have A/C vents that vent air directly to the windscreen. In my case there are number of buttons to change where the A/C draft should come. To the bust area, to the leg area, both to the bust area and leg area and then there's the button to send it to the windscreen.
If at all if you have missed this you could select an appropriate button or lever position or whatever to reduce or stop the AC flow to the windscreen. But most probably this feature is missing from your vehicle. In which case a solution would be as suggested above is to keep the AC blower to a not so high value..