cyclotorsion

Cyclotorsion is the rotation of the eye about its visual axis, a torsional movement of the globe that can change the orientation of ocular structures such as the cornea and iris. In ophthalmology and vision science, it refers to the angular displacement of the eye around the line of sight, which can affect how refractive errors present to the retina.

It can occur during fixation, with rapid eye movements, or as part of the vestibulo-ocular reflex when the head is tilted. The resulting torsion is often small, measured in degrees, but even modest rotations can influence the alignment of astigmatic corrections.

Clinically, cyclotorsion is most relevant in precision procedures that depend on stable axis orientation, such as refractive surgery (for example LASIK and PRK) and toric intraocular lens implantation. If uncorrected, cyclotorsion can rotate the planned astigmatic axis between preoperative assessment and treatment, leading to residual refractive error. Modern platforms frequently incorporate real-time eye tracking and cyclotorsion compensation to maintain alignment with the eye’s instantaneous orientation.

Measurement and assessment techniques include tracking iris landmarks or Purkinje images, corneal topography and keratometry performed in different head or posture positions, and wavefront-based approaches. These methods help quantify torsional drift and guide compensatory adjustments during surgery.

In sum, cyclotorsion describes a physiologic and clinically important eye rotation around the visual axis, with direct implications for the accuracy of astigmatic correction in ophthalmic procedures.