Measuring Ocular Torsion

   It's easy to see that the eyes move up, down, or right-to-left; but they also rotate from side to side, a motion we call torsion. Certain eye movement problems can be associated with torsional abnormalities, and these can be measured using two lens-like devices called Maddox rods, mounted in a trial frame. The most common condition associated with torsional problems is acquired weakness of the fourth cranial nerve, which provides stimulation for the superior oblique muscle.