Extraocular Motility Revision

Question 1

What is the length of the EOM?

Answer 1

Roughly 40mm (IO slightly shorter)

Question 2

Where do the 4 recti muscles originate from?

Answer 2

The apex of the orbit, at the level of the annulus of Zinn

Question 3

Where do the recti muscles insert? Where do the obliques insert?

Answer 3

Inserted in front of the ocular equator, obliques are inserted behind.

Question 4

Medial rectus action and innervation?

Answer 4

Adduction (towards from midline of body)

Inferior division of oculomotor nerve (CN3)

Question 5

Lateral rectus action and innervation

Answer 5

Abduction (away from the midline of the body) 
Abducens nerve (CN6)

Question 6

Superior rectus action and innervation

Answer 6

Main action Elevates

Secondary action intorsion (rotation)

Tertiary action is adducts (towards nose)

Innervation superior devision of oculomotor nerve (3rd)

Question 7

Inferior rectus

Answer 7

Main: depression
Secondary: extortion
Tertiary action: adduction (towards midline)
Innervation: inferior division of oculomotor nerve CN3

Question 8

Superior oblique

Answer 8

Main: depression
Secondary: intorsion
Tertiary: abduction (away from midline)
Innervation: trochlear nerve (cn6)

Question 9

Inferior oblique

Answer 9

Main: elevation
Secondary: extortion
Tertiary: abduction (away from midline)
Innervation: inferior devision of oculomotor nerve cn3

Question 10

RADSIN

Answer 10

Recti adduct

Superiors intort