I thought this was interesting.
ARE TWO EYES BETTER THAN ONE?
Bowen (1985) reports: "When low-contrast targets are viewed, there is a 40% improvement in resolution with binocular as compared to monocular vision. Binocular vision also gives an improvement in contrast sensitivity on the order of 40%. Also, there is a lower light threshold; there is a 25-40% gain in the ability to see faint objects."
http://www.fortunecity.com/roswell/borley/49/visual.htm