NBEO Ocular Motility Practice Test

Intorsion and extorsion are the eye’s twisting motions around the line of sight. In the axis system used for this test, that twisting axis is labeled as the vertical Y axis. So these torsional movements are described as rotations about the Y axis. Think of the eye twisting so the top moves toward the nose (intorsion) or away from the nose toward the ear (extorsion). Rotations about other axes would produce different kinds of movement (tilting up/down or rotating around the front-to-back line) and don’t describe torsion in this context.