Drisgirl - when you temporarily lose sight in one eye it is very disorientating, Your vision is skewiff and you bump in to things - even walking is difficult. You can't imagine ever being able to drive.
But if you are born with sight in only one eye, or vision is lost permanently, you do adapt and have perfectly good vision. You learn to turn your head slightly more and more often to get an all round field of vision comparable with people with sight in both eyes. It really is not a problem, which is why the DVLA allow one sighted people to hold a car driving licence,