Myopes often have double vision in one eye when they are looking at distant objects. The uniocular diplopia does not appear when the eyes are looking at near objects. Emmetropes or hyperopes never have uniocular diplopia. Among 100 myopes, 84 (84%) experienced far-sighted uniocular diplopia. Their mean ± SE myopic range was -3.89 ± 0.09 D. Among the subjects with uniocular diplopia, 98% had vertical diplopia and only 2% oblique diplopia. Their cornea, anterior chamber, and vitreous body were normal; the ocular fundi showed myopic degeneration. The anterior surface of the crystalline lens cortex showed protrusion, indicating stronger convexity than the capsule surface of the lenses. Uniocular polyopia frequently appears in immature cataract eyes when viewing distant objects. Polyopia is caused by the lamellar opacities of the lens, effected by the different refraction in a lens. According to this experiment, uniocular diplopia can be caused by the different refraction in a lens that results in the different convexities of the capsule and cortex.