Eye Muscles etc.

Question 1

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

Answer 1

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

Question 2

What is diplopia?

Answer 2

Double vision (the perception of 2 imgaes of a single object)

Question 3

Disorders of which nerves are characterised by diplopia?

Answer 3

Occulomotor - CN III
Trochlear - CN IV
Abducens - CNVI

Question 4

How would you examine a patients eye movements?

Answer 4

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

Question 5

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

Answer 5

1) Ciliary muscle - changes shape of the lens in the process of accomodation (allowing lens to thicken for near vision)
2) Sphincter pupillae - muscle of iris which constricts pupil
3) Dilator pupillae - muscle of iris which dilates pupil

Question 6

Give 2 examples of non-neurological causes of eye movement abnormalities?

Answer 6

1) Defects of the extra occular muscles

2) Defects of the neuromuscular junction

Question 7

How is the function of the occulomotor nerve specifically tested?

Answer 7

Ask the patients to look medially - check that the upper lid is fully retracted on upward gaze

Question 8

What are the 7 extraoccular muscles?

Answer 8

The 6 that move the eye plus levator palpebrae superioris

Question 9

How is the function of the abducens nerve tested specifically?

Answer 9

Ask the patient to look laterally

Question 10

Paralysis of the lateral rectus muscle results in what?

Answer 10

Inward squint

Question 11

How is the function of the trochlear nerve tested specifically?

Answer 11

Ask the patient to look medially and then downwards

Question 12

What is the function of levator palpebrae superioris?

Answer 12

Elevation of the upper eyelid

Question 13

What is ptosis?

Answer 13

Drooping of the upper eyelid

Question 14

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

Answer 14

Smooth muscle called superior tarsal muscle

Question 15

Ptosis results from malfunction of which muscles?

Answer 15

Levator palpebrae superioris

Superior tarsal muscle

Question 16

What is Horner’s syndrome?

Answer 16

A condition resulting from the interruption of sympathetic pathways to the eye resulting in:

1) Ptosis on the same side
2) Miosis on the same side
3) Anhidosis on the same side
4) Flushing on the affected side

Question 17

What is meant by miosis?

Answer 17

Constriction of the pupil

Question 18

What is meant by anhidosis?

Answer 18

Absence of sweating

Question 19

Why does mild ptosis occur in Horner’s syndrome?

Answer 19

The superior tarsal muscle receives sympathetic innervation so interruption to this results in paralysis of superior tarsal leading to mild ptosis
NB. The superior tarsal muscle smooth muscle is sometimes considered as part of the levator palpabrae superioris so some textbooks say the levator palpebrae superioris receives some sympathetic innervation

Question 20

Which eye muscles are involved in the movements in the test for the occulomotor nerve?

Answer 20

Look medially - Medial rectus (look medially)
Look upwards - Inferior rectus (look medially and upwards) and superior oblique (look laterally and upwards)
Eyelid retracted on upwards gaze - levator palpebrae superioris

Question 21

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

Answer 21

Look laterally - lateral rectus (look laterally)

Question 22

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

Answer 22

Look medially and then downwards - superior oblique (look medial and downwards)

Question 23

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

Answer 23

1) Sphincter pupillae

2) Ciliary muscle

Question 24

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

Answer 24

Supplies parasympathetic fibres via the ciliary ganglion

Question 25

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

Answer 25

Parasympathetic constricts

Sympathetic dilates

Question 26

Dilator pupillae is innervated by what via what?

Answer 26

Innervated by fibres from the sympathetic chain

Via the superior cervical ganglion

Question 27

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 27

Accommodation reflex
Afferent limb = optic nerve
Efferent limb = oculomotor

Pupillary light reflex
Afferent limb = optic nerve
Efferent limb = oculomotor nerve

Question 28

4 possible causes of oculomotor nerve damage?

Answer 28

1) Berry aneurysm at junction between the posterior communicating and internal carotid a.
2) Diabetic peripheral neuropathy - most common cranial nerve disease in people with diabetes
3) Lesion anywhere along the nerve
4) Severe head injury

Question 29

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

Answer 29

Horner’s = partial ptosis only, miosis (constricted pupil), anhidosis (dry skin with this) and flushing
Early R oculomotor palsy = Complete ptosis, mydriasis (dilated pupil)

Question 30

What is meant by mydriasis?

Answer 30

Dilated pupil