Eye Muscles etc. Flashcards
What 6 muscles are involved in eye movement, what is their innervation?
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
What is diplopia?
Double vision (the perception of 2 imgaes of a single object)
Disorders of which nerves are characterised by diplopia?
Occulomotor - CN III
Trochlear - CN IV
Abducens - CNVI
How would you examine a patients eye movements?
Draw 2 large H’s and ask patient to follow your finger
What are the 3 intraoccular muscles and what is their function?
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
Give 2 examples of non-neurological causes of eye movement abnormalities?
1) Defects of the extra occular muscles
2) Defects of the neuromuscular junction
How is the function of the occulomotor nerve specifically tested?
Ask the patients to look medially - check that the upper lid is fully retracted on upward gaze
What are the 7 extraoccular muscles?
The 6 that move the eye plus levator palpebrae superioris
How is the function of the abducens nerve tested specifically?
Ask the patient to look laterally
Paralysis of the lateral rectus muscle results in what?
Inward squint
How is the function of the trochlear nerve tested specifically?
Ask the patient to look medially and then downwards
What is the function of levator palpebrae superioris?
Elevation of the upper eyelid
What is ptosis?
Drooping of the upper eyelid
Other than levator palpebrae superioris, which 1 other muscle is involved in elevation of the upper eyelid?
Smooth muscle called superior tarsal muscle
Ptosis results from malfunction of which muscles?
Levator palpebrae superioris
Superior tarsal muscle
What is Horner’s syndrome?
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
What is meant by miosis?
Constriction of the pupil
What is meant by anhidosis?
Absence of sweating
Why does mild ptosis occur in Horner’s syndrome?
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
Which eye muscles are involved in the movements in the test for the occulomotor nerve?
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
Which eye muscle is involved in the test for the abducens nerve?
Look laterally - lateral rectus (look laterally)
Which eye muscles are involved in the test for the trochlear nerve?
Look medially and then downwards - superior oblique (look medial and downwards)
Which intraocular muscles are supplied by the oculomotor nerve via the ciliary ganglion?
1) Sphincter pupillae
2) Ciliary muscle
The occulomotor nerve supplies what kind of fibres to the intraocular muscles via what?
Supplies parasympathetic fibres via the ciliary ganglion