Cyclotorsion as a structural and functional biomarker of ocular and neuroophthalmic diseases.

Cyclotorsion, defined as rotation of the eye around its anteroposterior axis, is an important but often underrecognized component of ocular motility. This review summarizes the physiological basis of cyclotorsion, methods of subjective and objective assessment, and the clinical relevance of torsional deviations in ocular and neuro-ophthalmic disorders. Particular emphasis is placed on objective measurement using the disc-foveal angle and its role in diagnosing and monitoring conditions such as trochlear nerve palsy, skew deviation, pulley disorders, inferior oblique overaction, thyroid eye disease, heavy eye syndrome, and sagging eye syndrome. Quantitative assessment of cyclotorsion may improve diagnostic accuracy, support surgical planning, and provide an objective marker of treatment outcome.