Lecture 16- Extraocular eye muscles

Question 1

Why binocular vision?

Answer 1

• Allows wider field of vision and depth perception
• Enabling 3D – stereoscopic vision

Question 2

to allow binocular vision

Answer 2

• Visual axis of both eyes need to be aligned
• Eyes need to coordinate and move together- conjugate eye movement
  
  • Two images that reach cortex are fused, perceived as one

Question 3

Misalignment of visual axes causes

Answer 3

diplopia

Question 4

diplopia

Answer 4

• Misalignment of 2 visual axes image focuses on different area of each retina
  
  • Brain unable to fuse- 2 separates images diplopia
    
    • Can be displaced horizontally, vertically or diagonally

Question 5

function of Extra ocular muscles

Answer 5

Allow eyes to move together in order to maintain fixation on image

Question 6

how many muscles move the eyeball

Answer 6

6

Question 7

where are extraocular muscles attached to

Answer 7

the sclera

Question 8

where do the extraocular muscle originate from

Answer 8

• All originate in apex of orbit (except Inferior Oblique- arises floor or orbital cavity anteriorly)
• 4 recti arise from a common tendinous ring

Question 9

where does the inferior oblique arise from

Question 10

which CN innervates most of the extraoccular eye muscles and which muscles are not innervated by this nerve

Answer 10

CN III - oculomotor

lateral rectus

superior oblique

Question 11

which nerve innervates the lacteral rectus

Answer 11

CNIV- trochlear

Question 12

which nerve innervates the superior oblique

Answer 12

VI- abducens

Question 13

• Nerve innervation remembered as:

Answer 13

• LR6 SO4
  
  • Lateral rectus- abducens CN VI
  • SO4- superior oblique- trochlear – CN IV

Question 14

• Each muscle will have certain

Answer 14

pull and action on eye movement

Question 15

the 6 muscles of the eye are either

Answer 15

recti (4)

oblique (2)

Question 16

4 recti

Answer 16

• Superior
• Inferior
• Medial
• Lateral

Question 17

2 oblique

*

Answer 17

• Superior
• Inferior

Question 19

axis of pull made up of

Answer 19

• Axis of the eyeball (visual axis)
• Axis of orbit

Question 20

• Extraocular muscles run in line with axis of

Answer 20

orbit

• Therefore some muscles attach at an oblique angle
  
  • Attaching to superior and inferior surfaces of globe
• Confers several actions of movement on globe (not simply up and down) for some of the extra ocular muscles)

Question 21

3D MODEL- right eye

Answer 21

1- superior rectus muscle

2- lateral rectus

3- superior oblique muscle

• Passes through a pullé which swing muscle back inserting into the posterior lateral surface of the superior surface of the eye

4-medial rectus

5- common tendinous ring

Question 22

posititon at rest

Answer 22

primary resting gaze

Question 23

outline how the primary resting gaze is maintained

Answer 23

• Equal and opposite pull of all extraocular muscles
• even at rest constancy of activity in all extra ocular muscles on eyeball
• during resting gaze their actions are balanced allwoing for forward gaze
  *

Question 24

how can equal and opposite pull of extraocular muscles during primary resting gaze be maintained

Answer 24

each muscle shas antagonists of its movement

Question 25

**Changing position of gaze**

Answer 25

Exert greater pull through action of certain extraocular muscles, while antagonists relax - muscles moving **both eyes** must be highly coordinated and move simulataneously - visual axis must remain aligned (conjugate gaze) - if visual axes do not remain aligned (diplopia - double vision)

Question 26

terms of direction- medial towards nose

Answer 26

aDducted

Question 27

lateral movement of eye

Answer 27

aBducted

Question 28

superior movement of eye

Answer 28

elevation

Question 29

inferior movemnt of eye

Answer 29

depression

Question 30

external rotation

Answer 30

extortion

Question 31

internal rotation

Answer 31

intorsion