Wiktionary
see double
vb. To experience double vision, wherein the eyes do not focus on the same point and a single object is therefore perceived as two.
WordNet
see double
v. see things as if they were there twice; "After taking the drug, John saw double"
Usage examples of "see double".
Somehow, when they cross those two halves of the brain for greater keenness, they see double.
But they not only see double, but by some psychological trick, they see the wrong image best!
I felt a tug at my short sleeve, and looked over to see Double Bill offering me a smoldering spliff.