Eye muscles

Question 1

What 6 muscles are involved in eye movement, and what is their innervation?

Answer 1

1) Superior oblique - IV
2) Inferior oblique - III
3) Superior rectus- III
4) Lateral rectus - VI
5) Inferior rectus - III
6) Medial rectus - III

Question 2

What is diplopia?

Answer 2

Double vision

Question 3

What nerves cause diplopia?

Answer 3

Occulomotor - III
Trochlear - IV
Abducens - VI

Question 4

How would you examine eye movements?

Answer 4

Draw 2 H’s and ask the patient to follow your finger

Question 5

What are the 3 intraoccular muscles and what is their function?

Answer 5

CILIARY MUSCLE - changes lens shape (ie thickens for near vision)
SPHINCTER PUPILLAE - iris muscle which constricts pupil
DILATOR PUPILLAE - iris muscles that dilates pupil

Question 6

What are 2 non-neurological causes of eye movement abnormalities?

Answer 6

• Defects of extra occular muscles

- Defects of NMJ

Question 7

How is the function of the occulomotor nerve specifically tested?

Answer 7

Ask patient to look medially

- check upper lid is fully retracted on upward gaze

Question 8

What is the 7th extraoccular muscle

Answer 8

Levator palpebrae superioris

Question 9

How is the function of the abducens nerve tested specifically?

Answer 9

Ask patient to look laterally

Question 10

Paralysis of the lateral rectus muscle results in what?

Answer 10

Inward squint

Question 11

How is the trochlear nerve function tested?

Answer 11

Ask patient to look medially then down

Question 12

What is the function of levator palpebrae superioris?

Answer 12

Elevation of upper eyelid

Question 13

What is ptosis?

Answer 13

Drooping of upper eyelid

Question 14

Other than levator palpebrae superioris, which 1 other muscle is involved in elevation of the upper eyelid?

Answer 14

Superior tarsal muscle

Question 15

Ptosis results from malfunction of which muscles?

Answer 15

Levator palpebrae superioris

Superior tarsal

Question 16

What is Horner’s syndrome?

Answer 16

Interruption of sympathetic pathways to eye&raquo_space;

• mild ptosis
• miosis
• anhidrosis
• flushing

Question 17

What is miosis?

Answer 17

Constriction of the pupil

Question 18

Why does mild ptosis occur in Horner’s syndrome?

Answer 18

Paralysis of superior tarsal muscle (sympathetic innervation)

Question 19

Which eye muscle is involved in the test for the abducens nerve?

Answer 19

Lateral rectus (look lat)

Question 20

Which eye muscles are involved in the test for the trochlear nerve?

Answer 20

Superior oblique (look med then down)

Question 21

Which intraocular muscles are supplied by the oculomotor nerve via the ciliary ganglion? (2)

Answer 21

Sphincter pupillae

Ciliary muscle

Question 22

The occulomotor nerve supplies what kind of fibres to the intraocular muscles via what?

Answer 22

Parasympathetic fibres via ciliary ganglion

Question 23

Dilation and constriction of the pupil are each controlled by what parts of the autonomic nervous system?

Answer 23

Parasympathetic - constriction

Sympathetic - dilation

Question 24

What innervates dilator pupillae?

Answer 24

Fibres from sympathetic chain via superior cervical ganglion

Question 25

Which 2 visual reflexes would be absent in a patient with unilateral oculomotor nerve damage? What other cranial nerves are involved in these reflexes?

Answer 25

Accommodation reflex

• Optic nerve (afferent)
• Occulomotor nerve (efferent)

Question 26

4 possible causes of oculomotor nerve damage?

Answer 26

• Berry aneurysm
• Diabetic peripheral neuropathy
• Lesion
• Severe head injury

Question 27

How would you distinguish between Horner’s syndrome and early right occulomotor palsy?

Answer 27

HORNER’S - partial ptosis only

• miosis (constricted pupil)
• anhidrosis
• flushing

OCCULOMOTOR PALSY - complete ptosis
- mydriasis (dilated pupil)

Question 28

What is mydriasis?

Answer 28

Dilated pupil