lateral rectus
Also called LR, lateral rectus muscle, external rectus
The horizontal extraocular muscle on the temporal side of the globe. It arises from the annulus of Zinn, the ring of connective tissue at the back of the orbit, inserts 6.9 mm behind the temporal edge of the cornea, and its only action from primary position is abduction, turning the eye outward1.
Its antagonist is the medial rectus of the same eye and its yoke, the muscle in the fellow eye that moves with it, is that eye's medial rectus. The abducens nerve, the sixth cranial nerve, supplies it and no other muscle, so weakness produces an esotropia largest in gaze toward the affected side and at distance2,3.
More detail
Because its plane contains the line of sight, contraction rotates the eye about the vertical axis alone, with no vertical or torsional component. When the eye is already raised or lowered the muscle gains a small vertical pull, which explains the upshoot and downshoot of the adducted eye in Duane syndrome2. The nerve enters the muscle 15 mm from its origin2.
Sources (3)
- Kanski, Clinical Ophthalmology (2024), ch. 18
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 3 and ch. 4
- Adler's Physiology of the Eye, ch. 7, Table 7.1
Reviewed October 2026