Ocular torsions and the subjective visual vertical with central vestibulo-ocular system lesions: independence disproved

Objectives Torsions of the eyes and deviations of the subjective visual vertical in roll occur regularly with disorders of the central vestibulo-ocular system. Although nearly universally coexisting, torsions and deviation have been held to be more or less independent of each other. Materials and methods Angles of torsion were determined from fundus photographs in 55 subjects representing a variety of acute, focal, brainstem or cerebellar lesions. Measured torsions were contrasted with quantitative measurements of the subjective visual vertical. Results Torsions and deviations proved to be directly proportional, with a direction coefficient close to unity, and were strongly correlated (r = 0.86). Conclusions Torsions and deviations are strongly dependent. This result should allow the generation of a more transparent pathophysiological model. From a practical point of view, measurements of deviation appeared more robust than those of torsion.