Observations about objective and subjective ocular torsion.

OBJECTIVE To investigate the relationship between objective and subjective torsion in patients with cyclovertical strabismus and determine whether objective torsion differs according to which eye is fixing. DESIGN A prospective evaluation of tests of objective and subjective torsion. PARTICIPANTS Thirty-six patients with various types of cyclovertical strabismus. METHODS Subjective torsion was assessed with the double Maddox rod, and objective torsion was graded in a masked manner from fundus photographs. MAIN OUTCOME MEASURES Quantification of objective or subjective torsion. RESULTS Objective torsion was the same regardless of which eye was used for fixation. However, after prolonged occlusion of the nonaffected eye, there was often an increase in objective torsion in the nonaffected eye. Subjective torsion typically was absent in patients with objective torsion if they did not have bifoveal fusion but was similar to objective torsion in patients with bifoveal fusional potential. CONCLUSIONS Assessment of objective and subjective torsion are each important but play separate roles in the evaluation of cyclovertical strabismus. There is no immediate torsional motor shift when fixation switches from the nonaffected to the affected eye. However, prolonged fixation of the affected eye may possibly result in a motor torsional change in the nonaffected eye in some patients.