Monocular vs Binocular Diplopia This document discusses the differences between monocular and binocular diplopia. Monocular diplopia occurs when a patient sees double vision with one eye open. Binocular diplopia occurs when a patient sees double vision with both eyes open. The document outlines various causes, testing methods, and treatment approaches for each type of diplopia. Physiologic diplopia, which occurs when viewing objects off the horopter curve, is also discussed.