Then again there's supernormal vision.
Research adapted from adaptive optics has shown that human vision can be improved to twice that of normal visual acuity:
Supernormal Vision
A focus on adaptive optics improves images of the eye and boosts vision.
http://www.sciencenews.org/pages/sn_arc97/11_15_97/bob1.htm
Supernormal Vision.
http://www.opt.indiana.edu/people/faculty/miller/SVision.html
I once suggested to some Mars imaging scientists that such devices be used to improve Mars imaging analysis, but to no avail.
Bob Clark