extorsion /ex·tor·sion/ (eks-tor´shun) outward rotation of the upper pole of the vertical meridian of each eye.
ex·tor·sion ( k-stôr sh n)n. 1. The outward rotation of a limb or organ. 2. The outward divergent rotation of the upper poles of the vertical meridian of the cornea of each eye. Also called disclination, positive declination. |
extorsion
rotation of the pupil, observed only in animals with horizontal pupils such as cattle and sheep. Caused by paralysis of the dorsal oblique muscle, as seen in polioencephalomalacia of ruminants.
torsion
Rotation of an eye about an anteroposterior axis. If the upper pole of the vertical meridian of the cornea appears to rotate inward, it is called intorsion, and outward, extorsion. If the eye rotates to the right it may be called dextrotorsion and if it rotates to the left it may be called laevotorsion. It may occur as a result of a head tilt, extraocular muscle weakness or rotation of the eye to a tertiary position. Syn. cycloductin; cyclorotation; torsional movement. See Donder's law; tertiary position; incongruous hemianopia.
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