Name the muscles of eye movement
Superior, inferior, lateral, medial rectus Superior oblique Inferior oblique
Action of the superior rectus? Innervation?
Elevates, rotates and adducts eyeball medially
(Inserts slightly medially to eye's vertical axis of rotation)
Action of the inferior rectus?
Depresses, adducts and rotates eyeball laterally
(Inserts slightly medially)
Action of the medial rectus?
Action of the lateral rectus?
Attachements and course of the superior oblique?
Originates from body of sphenoid bone. Tendon passes through trochlea, changes direction to go laterally, attaches to posterior surface of eye
What are the actions of the superior oblique?
Primary action: Intorsion (internal rotation)
Secondary action: Depression in adducted position (reading)
Tertiary action: Abduction
What does the superior oblique muscle do when acting alone?
Moves eye down and out
Attachments of the inferior oblique?
Originates from anterior part of the floor of the orbit and attaches deep to the lateral rectus, comes underneath the eye.
Actions of the inferior oblique?
Abducts, elevates and laterally rotates the eyeball
What is the equation for the innervation of the eye muscles?
LR6 SO4 R3
Innervation of the eye muscles?
Lateral rectus = CN VI - abducens nerve
Superior oblique = CN IV - trochlear nerve
All the rest = CN III - oculomotor nerve
What protects the cornea and eyeballs from injury, irritation and drying out?
Eyelids and lacrimal glands
Layers of the upper eyelid?
Fibres of orbicularis ori
Levator palpebrae superioris
What is the superior tarsus?
Dense connective tissue, a strengthening skeleton
Called the inferior tarsus on the lower lid
Superior tarsus muscle connects to it
What does the tarsal/Meibomian gland secrete?
Secrete oil - sebaceous
Prevent evaporation of the eye's tear film, preventing the eye from drying out
What are styes?
Blockage of the ciliary glands
What triggers reflex bilateral blinking?
Expectation of contact
Corneal blink/reflex (CN V and VII)
Which muscles open the eyelids?
Levator palpebrae superioris (oculomotor) and superior tarsal muscles (sympathetic)
Which muscle closes the eyelids? Innervation?
What can happen if there is paralysis of the orbicularis oculi muscle?
Failure to close eyes eg Bell's palsy
Get loss of blink and corneal reflex
Dry eye, high chance of infection
What can happen if there is paralysis of the levator palpebrae superioris?
Drooping of upper eyelid - ptosis
Vision is compromised
Have residual opening of the eye due to superior tarsal muscle (smooth muscle)
What happens if there is paralysis of the supeior tarsal muscle?
Vision usually ok
Eye opening ok due to LPS
Seen in Horner's syndrome with pupil constriction etc.
Function of lacrimal fluid?
Moistens and lubricates surface of conjunctiva
Provides some nutrients and oxygen
Innervation of the lacrimal glands?
Parasympathetic fibres of the facial nerve
Sensory supply via lacrimal branch of the ophthalmic division of CNV which also goes to eyelid and conjunctiva
Where do tears produced by the lacrimal gland go?
Tears drain out of the punctum in the medial eyelids, flow down the lacrimal canal into the lacrimal sac. They then drain down the nasolacrimal duct into the inferior meatus of the nasal cavity.
What is seen when there is damage to the oculomotor nerve?
Superior eyelid droops (innervates LPS) and cannot be raised due to unopposed action of orbicularis oculi
Pupil is fully dilated and non-reactive (sphincter pupillae) due to unopposed action of dilator pupillae
Pupil is down and out - unopposed action of lateral rectus and superior oblique
Action of the ciliary muscle?
Changes the shape of the lens within the eye
Which nerve is damaged if the patient cannot abduct their eye and why?
Fully adducted by unopposed action of the medial rectus
Innervates the lateral rectus