1. EXTRAOCULAR
MUSCLES
RANGEEN CHANDRAN R

2. ORBITAL MUSCLES
 Extrinsic muscles of eyeball.
 Involved in movement of eyeball.
 Intrinsic muscles
 Controls shape of lens and size of pupil.

3. Extraocular muscles are special
 The motor units are small, with only from 5 to 18 muscle
fibers contact by each motor nerve

4. Motion of an Eye
 To describe eye motions we need a set of defined axes (Fick’s
Axes - draw on board)
 X axis : nasal -> temporal
 Y axis: anterior -> posterior
 Z axis: superior -> inferior
 These axes intersect at the center of rotation - a fixed point,
defined as 13.5 mm behind cornea.

5. AXES OF EYEBALL AND ORBIT

6. Ductions (single eye movements)
 Rotation about the Z axis (Z axis runs vertically superior to
inferior)
 Medial Rotation - adduction toward midline
 Lateral Rotation - abduction away from midline
 Rotation about the X axis (X axis runs horizontally, from
nasal to temporal)
 Upward, elevation (supraduction)
 Downward, depression (infraduction)

7. Torsion - cyclorotations
 Rotation about the Y axis (Y axis runs horizontally, from anterior
to posterior)
 These are described with respect to a point at 12 o‘clock on the
superior limbus
 Intorsion (incyclorotation) rotation nasally
 Extorsion (excyclorotation) rotation of the 12 o’clock position
temporally.
 Counteracting head tilt (up to 7-9°)

8. Version & Vergences
 Some eye movements are paired, that is both eyes do
the same thing. . . . Versions
 Sometimes eyes move in the opposite directions
simultaneously. . . Vergences

9. Vergences
 Disjunctive eye movements (opposite left- right
movments). Non-yolked motion
 Convergence (simultaneous movement nasally)
 Divergence (simultaneous temporal movement)
 Encyclovergence (intorsion)
 Excyclovergence (extorsion)

10. Versions (conjugate eye
movement)
 Dextroversion - rightward gaze (demo)
 Levoversion - leftward gaze
 Supraversion - elevation
 Infraversion - depression
 Also up and right, up and left
 Down and right, down and left
ALL BEHAVIOR IS THAT OF YOLKED
EYES

11. Extraocular muscles
 VOLUNTARY MUSCLES
 INVOLUNTARY MUSCLES

12. INVOLUNTARY MUSCLES
3 muscles.
 Superior tarsal muscle.
 Inferior tarsal muscle.
 Orbitalis.

13. VOLUNTARY MUSCLES
7 in number
 Levator palpebrae superioris
 Superior rectus
 Inferior rectus
 Medial rectus
 Lateral rectus
 Superior oblique
 Inferior oblique

15. LEVATOR PALPEBRAE
SUPERIORIS
 Superior most muscle in
the orbit.
 Has voluntary and
involuntary parts.

16.  Origin-Inferior surface of lesser wing of sphenoid.
 Insertion-
1. Upper lamina-Anterior surface of
superior tarsus and skin of upper eyelid.
2. Middle lamina-superior margin of
superior tarsus.
3. Lower lamina-Superior conjunctival
fornix
 NERVE SUPPLY-
Upper division of occulomotor nerve.

17. ACTION
 Elevation of upper eyelid.

18. Ptosis
Drooping of upper eyelid.
 Complete ptosis-injury to occulomotor nerve.
 Partial ptosis-disruption of postganglionic sympathetic
fibres from superior cervical sympathetic ganglion.

19. SUPERIOR RECTUS MUSCLE
 Origin-Superior part of common tendon of zinn.
 Insertion-inserted into sclera by flat tendinous
insertion(10mm broad)about 7.7 mm behind sclero-
corneal junction.
 Nerve supply-superior division of occulomotor nerve.

20. ANNULUS OF ZINN

21.  Frontal nerve runs above the superior rectus & levator.
 The nasociliary nerve and ophthalmic artery run
below.
 The tendon for insertion of the superior oblique
muscle runs below the anterior part of the superior
rectus.

22. Action of Superior Rectus
 Primary action is elevation . . But since the insertion on
the globe is lateral as well as superior, contraction will
produce rotation about the vertical axis toward midline
 Thus secondary action is adduction
 Finally, because the insertion is oblique, contraction
produces torsion nasally Intorsion.

23. INFERIOR RECTUS
 Origin-inferior part of common tendon of zinn
 Insertion-in the sclera 6.5 mm behind sclero corneal
junction.
 Nerve supply-inferior division occulomotor nerve.

24.  Fascial attachments below attached to inferior lid
coordinate depression and lid opening.
 Fascia below Inf. Rectus and Inf. Oblique contribute to
the suspensory ligament of lockwood.
 ACTIONS-
Primary depressor.
Subsidiary actions are adduction and extorsion.

25. MEDIAL RECTUS
 Origin-annulus of zinn and from optic nerve sheath.
 Insertion-in sclera 5.5mm behind sclero-corneal
junction.
 Nerve supply-lower division of occulomotor nerve.
 Fascial expansion from muscle sheath forms the medial
check ligament and attach to medial wall of orbit.

26.  Innervation is via cranial nerve III, the oculomotor
nerve, and the specific branch runs along the inside of
the muscle cone, on the lateral surface.
 The superior oblique, ophthalmic artery and nasociliary
nerve all lie above the medial rectus.
 ACTION-
Primary adductor of the eye.

27. LATERAL RECTUS
 Origin-annulus of zinn.
 Insertion-in the sclera 6.9mm behind sclerocorneal
junction.
 Nerve supply-abducens nerve which enters the muscle
on the medial surface.

28.  The lacrimal artery and nerve run along the superior
border.
 The abducens nerve, ophthalmic artery and ciliary
ganglion lie medial to the lateral rectus and between it
and the optic nerve.
 ACTION-
Primary abductor of eye.

29. SPIRAL OF TILLAUX
7.7
mm
5.5
mm
6.9
mm 6.5
mm

30. SUPERIOR OBLIQUE
 Longest and thinnest intraorbital muscle, the muscle
ends before the trochlea, tendon is 2.5 cm, smooth
movement through trochlea.
 Origin-body of sphenoid above and medial to optic
canal.Passes along superomedial part of orbit and ends
in a tendon.
 Insertion-Posterosuperior quadrant of sclera behind
equator of eyeball.
 Nerve supply-trochlear nerve entering it approximately
one third of the distance from the origin to the trochlea.

31. ACTIONS
 Primary action-intorsion.
 Subsidiary actions-abduction and depression.
 Adducted position-depression.

32. INFERIOR OBLIQUE
 Origin-Anteromedial part of orbital floor lateral to
nasolacrimal groove.
 Insertion-posteroinferior surface of globe near the
macula.
 Nerve supply-inferior division of occulomotor nerve
enters the muscle laterally at the junction of the inferior
oblique and inferior rectus muscles.

33. ACTIONS
 Primary action-extorsion.
 Subsidiary actions-elevations and abduction.
 Causes elevation only in adducted position of eyeball.

34. Origins/Insertions of Oblique
muscles

35. BLOOD SUPPLY
 Ophthalmic artery.
 Medial muscular branch-inferior rectus,
inferior oblique, medial rectus
 Lateral muscular branch-superior rectus
superior oblique, lateral rectus.