My dad was 88 and suffering from macular degeneration and was to the point of driving with one hand over one eye just to see straight. We were at his monthly eye doctor appointment when I asked the doctor as my dad sat there, "should my father drive the car anymore?" "Absolutely not!" he replied. Dad was pissed off at me for a month or so after that.
A year or so later he came up with the idea to let my mother drive, she had advanced Alzheimers and had forgotten who all of us were. Dad explained that he still knew the way to get around town by memory and he could just tell our mother where to turn, stop or park, etc.
