9.2 Eye movement disorders Flashcards
What is primary position, duction, version and strabismus of the eye?
Primary position: looking forward
Duction: rotation of the eye while it is moving alone
Version: movement of both eyes together
Strabismus: a misalignment or deviation of the visual axis
What is tropia and phoria?
Tropia: relative deviation of the visual axis with both eyes viewing (manifest misalignment)
Phoria: relative deviation of the visual axis with one eye covered (latent misalignment)
What is congenital strabismus and what are the causes?
Squint due to misalignment
Due to: defective central vision, other cause of impaired vision in one eye, anatomical disturbance, accomodative discrepancy
What are the types of congenital strabismus?
Concomitant: same in all positions
Intermittent: fine most of the time but may happen when tired
Latent: bought on by covering one eye
What are the nerves involved with the eye muscles?
III (superior, medial and inferior rectus and inferior oblique), IV (superior oblique), VI (lateral rectus)
What is the function of the 6 extraocular muscles
Superior rectus - elevates from abducted
Inferior rectus - depresses from abducted
Lateral rectus - abducts eye
Medial rectus - adducts eye
Inferior oblique - elevates from adducted
Superior oblique - depresses from adducted
What is the presentation of a III nerve palsy?
Complete ptosis, dilation of pupil, eye will be down and out
- Failure of elevation and adduction
What are the two divisions of III and what do they supply?
Superior: Superior rectus and levator palpibrae
Inferior: Inferior and medial rectus, inferior oblique and pupil/ciliary
What will you see in IV palsy?
Failure of abduction and inability to depress when adducted
Tend to get a head tilt away from the side of the lesion
How do you test for IV palsy?
Bielschowsky head tilt test - When you tilt the head the affected eye will be elevated as the superior oblique is unable to resist the movement
What will you see in VI palsy?
Failure of abduction
What happens in mysathenia gravis and how do you reverse it?
Eye muscle weakenss, ptosis and dipolopia reversed with IV tensilon
What are the 3 nuclear/internuclear lesions?
Gaze palsy, internuclear opthalmoplegia and one and a half syndrome
What do you see in a horizontal gaze palsy and what causes it ?
Cause by an abducens nucleus lesion - prevents the patient being able to look in the direction of the lesion
Where is the lesion in internuclea opthalmoplegia and what does it prevent?
In the medial longitudinal fasiculus - This prevents information from the VI nucleus going to the III nucleus leading to an inability of the C/L adduction when looking to the side of the lesion
e.g. if there is a lesion on the L side, when looking to the L the R eye will be unable to adduct in that direction
Where is the lesion in one and a half syndrome and what does it cause?
Lesion in the VI nucleus and the medial longitudinal fasiclus
Inability of everything except abduction of the good eye
What will you see in a supranuclear lesion and what does it mean?
Inability to look up and down when looking straight ahead - if you help you can cause the vestibuloocular reflex to drive the eyes down
This indicates that the connection is working fine but the brain cant access the information
What are the 5 types of eye movements?
Vestibular
Optokinetic - train phenomenon
Saccadic - rapid movement used when scanning (corrective phase in nystagmus)
Smooth pursuit - allows you to track movements
Convergence
What are the 5 types of saccades and what do they indicate?
Square wave jerks: involuntary to L/R before correcting, tend to occur when excited/stressed, 1 degree movement, non pathological
Macro square wave jerks: >7degree movement, indicates cerebellar issue
Flutter: back t back saccade - cerebellar
Opsoclonus
Voluntary nystagmus
What are the pathological nystagmus?
Vestibular: linear slow phase
Cerebellar/brainstem: exponentially decreasing slow phase
Congenital: exponentially increasing slow phase
In which direction of the nystagmus is the problem?
The direction of the slow phase
- The jerk is usually corrective
How can you tell central vs. peripheral vestibular nystagmus?
Pure vertical nystagmus = central
Peripheral can usually be overcome by vision (usually unidirectional)
What are the characteristics of cerebellar nystagmus?
Gaze evoked, fast phase in direction of gaze, slow phase exponentially decreasing
WHat is rebound nystagmus?
Wen you look out to one side you will get nystagmus and when you come back to the middle you will have it to that side
