cyclovertical muscles
The cyclovertical muscles are the superior rectus, inferior rectus, superior oblique, and inferior oblique, the four extraocular muscles that move the eye vertically. Each of these muscles also rotates the eye torsionally, so weakness of any one of them can cause vertical diplopia with tilted images.1,2
The horizontal recti control horizontal rotation, while each vertical rectus and each oblique controls a combination of vertical and torsional rotation. In the right eye, the superior rectus rotates the eye up and counterclockwise, the inferior oblique up and clockwise, the inferior rectus down and clockwise, and the superior oblique down and counterclockwise, with the torsional directions reversed in the left eye. Pure vertical or pure torsional rotation therefore requires the brain to activate a vertical rectus and an oblique together.2
Paralysis of a cyclovertical muscle invariably causes cyclotropia, and the cyclodeviation may appear in the normal eye when the patient fixates with the paretic eye. The Bielschowsky head tilt test applies to paresis of any cyclovertical muscle, although head tilt produces less vertical difference with a vertical rectus paresis than with an oblique paresis.3
More detail
The vertical planes containing the lines of pull of the vertically acting muscle pairs cross medially to the center of rotation of the eye, and the primary and secondary actions of these muscles follow from that single anatomical detail. The superior rectus and inferior oblique are the two elevators, and the superior rectus elevates most strongly when the eye is abducted. A superior rectus palsy therefore usually shows as restricted elevation with the eye turned outward.4
As the primary actions of the vertically acting muscles decrease, their secondary actions increase slightly. With the eye turned down and in, the inferior rectus pulls nearly at right angles to the visual axis and contributes little to depression, and its power to adduct and extort the eye increases. Muscle pulleys act as mechanical origins and modify these actions, so the simple vector analysis is a clinical approximation.4
Sources (7)
- Liu, Volpe and Galetta, Neuro-Ophthalmology: Diagnosis and Management, ch. 15
- Adler's Physiology of the Eye, ch. 9
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 20
- Pickwell's Binocular Vision Anomalies, ch. 17
- Remington, L. A. (2012). Clinical anatomy and physiology of the visual system. Elsevier Health Sciences.
- Khurana, A. K. (2019). Theory and practice of optics and refraction. Elsevier Health Sciences.
- Kushner, B. J. (2017). Strabismus. In W. Tasman & E. A. Jaeger (Eds.), Duane's Ophthalmology (2017 ed.). Lippincott Williams & Wilkins.
Reviewed October 2026
Related terms
Nearby in the glossary
- cross fixation
- crowding phenomenon
- cycloplegia
- cyclovertical muscles