Flashcards in FE: Lecture 2: Eye Movement Cranial Nerves Deck (24):
How does the eye compensate for the fovea being so small?
eye is constantly moving so the fovea can see whole image, movements must be fast
What does the term conjugate mean?
each eye gazes at the same point
What is diplopia?
double vision or two eyes looking at different things
this is a MOTOR problem not a sensory
What are two loss of reflexes that can occur in the eye?
Doll's eye reflex- looks right eyes goes left
What is the weirdness of the trochlear nerve?
exits dorsal side of brainstem (tectum)
crosses midline before exiting therefore:
1. left nucleus damage- right eye paralysis
2. left nerve damage after crossing- left eye paralysis
What are the different types of eye movements?
ADD, ABD, Elevation, depression, torsion, vergence, divergence and conjugate
How do you differentiate direction of torsion?
1. top of eye towards nose- medial rotation, intorsion
2. away from nose- external rotation, extorsion
these happen during side bend of the head
What does a conjugate eye movement mean?
when looking to left ------right eye- ADD, left eye ABD
What is convergence?
both eyes ADD
What is divergence?
both eyes ABD
What muscles control eye movements?
superior, inferior, medial, lateral rectus
superior and inferior oblique
What two muscles ABD and ADD eyes?
medial and lateral rectus
When the eye is ABDucted what are actions of the muscles?
obliques rotate- medially
When the eye is ADDucted what are the actions of the muscles?
What muscles work to contract to the right?
left medial rectus, right lateral rectus
What is the meaning of the mnemonic LR6SO4
lateral rectus is innervated by abducens nerve 6
superior oblique is innervated by trochlear nerve 4
all the rest are oculomotor
What is it called when you have damage to abducens nucleus or nerve?
pt has damage to both CN6 which leads to lateral rectus paralysis
they also have diplopia due to weak ABD
What is oculomotor palsy?
ipsilateral paralysis of all other muscles
weak add- medial rectus paralysis (ABD at rest)
weak elevation and depressing when ABD- SR/ IR
What other functions are damaged during oculomotor palsy?
drooping eyelids- ptosis b/c CN 3 opens eyelids (levator palpebrae)
also a dilated pupil- loss of parasympathetic innervation
What is trochlear palsy?
normal ipsilateral paralysis of superior oblique
weak depression of eye when ADDucted
torsional diplopia when looking forward
What is right side trochlear nerve palsy torsional compensation?
when your eyes are forward the eyes laterally rotate and slight elevate (hypertropia)
as a compensation the pt will tuck chin and tilt head to get rid of diplopia
Where are the cortical UMN's for nerves 3, 4 and 6?
cortical area 8/ Brodmann's 8
route- 1. middle frontal gyrus to PPRF then to pons for nuclei of 3, 4 and 6
this activation produces conjugate eye movements
What would happen if you had a lesion in B8?
no paralysis, temporary effects
hard to maintain contralateral eccentric eye position