5. Aset of six extraocular muscles (4 recti and 2 obliques) control the
movements of each eye.
Rectus muscles are:
• superior (SR),
• inferior (IR),
• medial (MR)
• lateral (LR).
The oblique muscles :
• superior (SO)
• inferior (IO).
VOLUNTARY MUSCLES
6. INVOLUNTARY MUSCLES
• There are three involuntary/smooth muscles
1. superior tarsal or Muller's muscle
2. inferior tarsal
3. orbitalis.
7. ORIGIN
• Rectus muscles originate from a common tendinous ring (the annulus of
Zinn).
• Medial rectus arises from the medial part of the ring,
• Superior rectus from the superior part of the ring also the adjoining dura
covering the optic nerve
• Inferior rectus from the inferior part
• Lateral rectus from the lateral part by two heads which join in a ‘V’form.
• All the four recti run forward around the eyeball
8. ORIGIN
• Superior oblique muscle arises from the bone above and medial to the optic
foramina.
• Inferior oblique muscle arises by a rounded tendon from the orbital plate of
maxilla just lateral to the orifice of the nasolacrimal duct.
9.
10. INSERTION
• All the four recti run forward around the eyeball and are inserted into the
sclera, by flat tendons at different distances from the limbus as under:
11. INSERTION
• Superior oblique muscle
inserted in the upper and outer part of the sclera behind the equator.
• Inferior oblique muscle
inserted into the lower and outer part of the sclera behind the equator.
12.
13. BLOOD SUPPLY
• EOM s receives their blood supply from muscular branches of ophthalmic
artery.
• Lacrimal artery LR
• Infraorbital artery IR,IO
14. NERVE SUPPLY
All striated ocular muscles are supplied by
Occulomotor nerve (except Superior oblique
and Lateral rectus)
•
•
Lateral rectus supplied by Abducen nerve
Superior oblique supplied by Trochlear
nerve
17. TYPES OF OCULAR MOVEMENT
• Unilateral movements are called ‘ductions’
1.Adduction It is inward movement (medial rotation) along the vertical axis.
2.Abduction It is outward movement (lateral rotation) along the vertical axis.
3.Supraduction It is upward movement (elevation) along the horizontal axis.
4. Infraduction It is downward movement (depression) along the horizontal axis.
5.Incycloduction (intorsion) It is a rotatory movement along the anteroposterior
axis in whichsuperior pole of the cornea (12 O’clock point)moves medially (internal
rotation).
6.Excycloduction (exextorsioIt is a rotatory movement along the anteroposterior
axis in which superior pole of the cornea (12 O’clock point) moves laterally (external
rotation).
18. TYPES OF OCULAR MOVEMENT
Versions, also known as conjugate movements, are
synchronous (simultaneous) symmetric movements
of both eyes in the same direction
• Binocular Movements
Vergences, also called disconjugate movements, are
synchronous and symmetric movements of both eyes
in opposite directions
21. • The extraocular muscles rotate the
eyeball around vertical, horizontal
and anteroposterior axes
• Medial and lateral rectus muscles
main action.
•Superior and Inferior rectus tendons
of the Superior and Inferior oblique
muscles subsidiary actions.
22.
23. SYNERGISTS, ANTAGONISTS AND YOKE MUSCLES
• 1. Synergists. If refer to the muscles having similar primary action in the same
eye
Eg: superior rectus and inferior oblique of the same eye act as synergistic
elevators.
• 2.Antagonists.These are the muscles having opposite actions in the same eye.
Eg: medial and lateral recti, superior and inferior recti and superior and inferior
obliques are antagonists to each other in the same eye.
24. • 3. Yoke muscles (contralateral synergists). These refers to the pair of muscles (one
from each eye) which contract simultaneously during version movements.
Eg:right lateral rectus and left medial rectus act as yoke muscles for dextroversion
movements.
• 4. Contralateral antagonists. These are a pair of muscles (one from each eye) having
opposite action;.
Eg: right LR and left LR, right MR and left MR.
25. LAWS GOVERNING OCULAR MOVEMENTS
• Hering’s law of equal innervation
According to law, an equal and simultaneous innervation flows from the brain to a pair
of muscles which contract simultaneously (yoke muscles) in different binocular
movements.
• Sherrington’s law of reciprocal innervation.
According to it, during ocular motility,increased flow of innervation to the contracting
muscle is accompanied by decreased flow of innervation to the relaxing antagonist
muscle
