17 Ocular Muscles, Movements and Testing

Question 1

Differentiate (in general terms) between the innervation of the extrinsic muscles of the eye and the intrinsic muscles of the eye. What muscles make up the intrinsic and extrinsic muscles of the eye?

Answer 1

Question 2

Why, even at primary resting gaze, is there still tone in the extraocular muscles of the eyeball?

Answer 2

Each muscle has antagonistic movement- during resting gaze actions= balanced

Visual axis aligned

Question 3

What will a patient have if their visual axes are maligned (don’t have conjugate gaze)?

Answer 3

Diplopia (double vision)

Question 4

There are 6 muscles that control the movement of the eyeball. Most of them are innervated by cranial nerve III (oculomotor). Which ones aren’t? (4 rectus muscles and 2 oblique muscles)

Answer 4

Lateral rectus= abducens (VI)

Superior oblique= trochlear (IV)

Superior, inferior and medial rectus= oculomotor (III)

Inferior rectus= oculomotor (III)

Question 5

Where do the 4 recti muscles of the eye orignate from?

Answer 5

Common tendinous ring

Question 6

State the actions of the 4 recti muscles of the eye.

Answer 6

• Medial rectus
  
  • Adducts eye
• Lateral rectus (abducens VI)
  
  • Abducts eye
• Superior rectus
  
  • Elevates eye
  • Adducts eye (slightly)
  • Internally rotates eye (slightly)
• Inferior rectus
  
  • Depresses eye
  • Abducts eye (slightly)
  • Externally rotates eye (slightly)

Question 7

State the origin and insertion of the superior oblque muscle of the eye.

Answer 7

Origin= sphenoid bone

Insertion= sclera of eye- posterior superior surface

(Passes through trochlea)

Question 8

State the actions of the superior oblique muscle of the eye.

(innervated by trochlear)

Answer 8

Intort (medially rotate)

Depress

Slightly abduct eye

Question 9

State the origin and insertion of internal oblique of the eye.

Answer 9

Origin= floor of orbit

Insertion= inferior surface on sclera of eyeball

Question 10

State the actions of the inferior oblique muscle of the eye.

Answer 10

Elevation

External rotation

Slight abduction

Question 11

How are the eye movements examined clinically?

Answer 11

Get patient to look at finger

Move finger slowly in H movement

1. Move finger horizontally first then vertical at each end

Question 12

What are the main muscles involved in elevation and depression of the eye when the eye is lateral (abducted)?

Answer 12

Superior rectus and inferior rectus

Question 13

What are the main elevators and depressors of the eye when the eye is adducted (in medial position)?

Answer 13

Inferior oblique and superior oblique

Question 14

Give some examples of how cranial nerve palseys can occur (affecting CNs III, IV and VI).

Answer 14

• Vascular disease:
  
  • diabetes
  • hypertension
• Raised intracranial pressure
  
  • intracranial haemorrhage/tumour

Question 15

If cranial nerve III (oculomotor) is affected by a vasculopathy (eg diabetes), how might this present differently to if the nerve is affected by compressive lesions eg (raised ICP, tumour, posterior communicating artery)

Answer 15

Question 16

How might a cranial nerve IV (trochlear) palsey present?

Answer 16

Question 17

How might a cranial nerve VI (abducens) palsey present?

Answer 17

Unable to abduct eye on affected side

Diplopia may be worse on horizontal gaze

Question 18

What is the most likely cause for CN injuries to CNs III, IV and VI?

Answer 18

Vasculopathic