2. Contents
Anatomy of EOM
• Origins & Insertions
• Nerve Supply
• Blood Supply
• Orbital Relations
Physiology of EOM
• Planes of Rotation
• Axes of Rotation
• Muscle Actions
3. Anatomy of EOM
Extraocular muscles are 7 extrinsic muscles attached
to the eyeball causing different movements of globe
and elevation of eyelid
These are
• Superior Rectus
• Inferior Rectus
• Medial Rectus
• Lateral Rectus
4. Anatomy of EOM (cont.)
• Superior Oblique
• Inferior Oblique
• Levator Palpebrae aa
Superioris
5. Embryology of EOM
• EOM originate from cranial mesoderm & neural crest
• From neural crest perimusclar connective tissue
develops about 3rd week of gestation
• Muscles originate from 3 separate points
• Each point is further innervated separately by
CN III,CN IV and CN VI
6. Embryology of EOM (cont.)
• Innervation supply is completed up to 1 month of
gestation
• Then the point innervated by CN III gives rise to
Medial Rectus, Superior Rectus, Inferior Rectus and
Inferior Oblique
• Points Innervated by CN IV and CN VI give rise to
Superior Oblique and Lateral Rectus respectively
7. Embryology of EOM (cont.)
• Levator muscle originates by splitting of Superior
Rectus
• Up to 6 months of gestation EOM are present in their
anatomical positions with surrounding tissues
• After that muscles just undergo through process of
growth
8. Structure of EOM
• Voluntary striated muscles
• Innervated by up to 10X more nerve fibers than
skeleton muscles
• Also have greater vascularity
• Consist of 2 layers:
1. Outer orbital layer (5-15um)
2. Inner global layer (10-50um)
9. Structure of EOM (cont.)
• Inner global layer consists of 3 type of fibers:
1. Red
2. Intermediate
3. White
10. Features of Fibers
1. Twitch fibers (11-15um)
2. Tone fibers (9-11um)
3. Singly innervated fibers
4. Multiply innervated fibers
11. Orbital Position of Globe
• The walls of bony orbit are divergent and thus orbital
axes pass through an angle of 23 degrees
• Angle between visual & orbital axis is about 22.5
degrees
12.
13. Origins & Insertions
MUSCLES ORIGINS TENDON
LENGTH
INSERTION
SR Tendinous Ring 5.8mm Sclera close to
limbus
IR Tendinous Ring 5.5mm Sclera close to
limbus
MR Tendinous Ring 3.7mm Sclera close to
limbus
LR Tendinous Ring 8.8mm Sclera close to
limbus
14. Origins & Insertions (cont.)
MUSCLES ORIGINS TENDON
LENGTH
INSERTION
SO Superomedial to
optic canal
26mm Superotemporal
quadrant of globe
IO Margin of orbital
floor lateral to
lacrimal fossa
1mm Inferotemporal
quadrant of globe
LPS Superior to
tendinous ring
from lesser wing
of sphenoid
14-20mm Eyelid skin and
tarsal plate
29. Orbital Relations (cont.)
• Muscle Pulleys are expansions of EOM mainly of
horizontal recti which control affect of horizontal
movements on vertical and vice versa.
33. Laws of Motility
• Sherrington law states that increased innervation to
agonist is accompanied with reciprocal decrease of
innervation to its antagonist
• Hering Law states that during a conjugate eye
movement an equal innervation flows to yolk
muscles of both eyes
34. EOM Actions
• Primary Action is the main effect of muscle
contraction on position of globe when globe is in
primary position
• Subsidiary Actions are other effects on position of
eye on muscle contraction in primary position
35. EOM Actions (cont.)
• Recruitment is innervation supplied to motor units
by brain to take fixation in a specific gaze
• Arc of contact is physiological point where muscle
first contacts globe
