lateral rectus
Also called LR, lateral rectus muscle, external rectus
The lateral rectus is the horizontal extraocular muscle on the temporal side of the globe, and the only muscle that abducts the eye from primary position. It arises from the annulus of Zinn at the back of the orbit and inserts 6.9 mm behind the temporal edge of the cornea1.
The abducens nerve supplies the lateral rectus and no other muscle, so weakness produces an esotropia that is largest in gaze toward the affected side and at distance2,3. The nerve enters the muscle 15 mm from its origin2.
Its plane contains the line of sight, so contraction rotates the eye about the vertical axis alone, with no vertical or torsional component. The antagonist of the lateral rectus is the medial rectus of the same eye, and its yoke is the medial rectus of the fellow eye.
More detail
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.
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