Well, by law, I think the person with one eye has to have better vision for that eye than is requried in each eye of someone with two.
And when you think about it, its becuase the government doesn't want to say that if something happens to one of your eyes, you will never be able to drive again.
From a more scientific standpoint, both eyes are only neccessary to evaluate depth, not so much detail. Assuming that this person was not born with one eye, the brain will fill in the gap left behind by the other eye, and he should be able to see fine (for the most part).
Eye exams still suck though right
