For an animal blessed with the seemingly incompatible traits of bone-china fragility, jiu-jitsu flight instincts, and combustion engine top-speeds, the horse is understandably yoked to its vision for avoiding harm's way. Because of that, sight is arguably the sense most artificially manipulated in the racehorse to "enhance" performance. Blinkers. Cheekpieces. Hoods to fool the recalcitrant into the starting gate. Mesh goggles for the fractious. Nor does the loss of an eye render a Thoroughbred's evolutionary purpose obsolete. Far from it. One-eyed wonders like Hard Not to Love--recent winner of the...