Blinding elements

Choose one elemental damage type, lightning, fire, cold, acid, poison. Whenever you deal this damage type anything hit by you must make a saving throw equal to your spell save dc or be blinded. If the spell already has a saving throw, when they make that save they avoid being blinded, if the spell does not already have a saving throw they must make a Constitution save equal to your spell save dc, And creature that has been blinded makes a Constitution save against your spell save dc on each of their turns after being blinded.