Session 9: Extra-ocular Eye Muscles, Action and Diplopia Flashcards
There are a total of six muscles controlling the movements of the eyeball.
Which?
Superior and inferior rectus
Superior and inferior oblique
Lateral and medial rectus
What is conjugate gaze?
The visual axes must remain aligned and conjugate gaze shows the eyes’ ability to work together and move in unison.
What happens if the visual axes is misaligned?
Diplopia
Movements the eye can move in.
Elevation and depression.
Abduction and adduction
Extortion and intortion
Explain the movement of medial rectus and lateral rectus.
Lateral rectus abducts the eyes
Medial rectus adducts the eyes
Innervation of medial and lateral rectus
MR - Oculumotor nerve
LR - Abducens nerve
Origin, insertion, action and innervation of Superior rectus.
Elevates the eyeball
Slightly adducts
Slight intorts
Arise from the apex of the orbit and inserts into superior anterolateral surface of the globe.
Innervated by the Oculumotor nerve.
Origin, insertion, action and innervation of inferior rectus muscle.
Depresses the eye
Slightly adducts
Slight extorts
Originates from the apex of the orbit and inserts into the anteroinferior surface of globe.
Innervated by Oculumotor
Origin, insertion, action and innervation of Superior oblique muscle.
Arise from the orbits, then passes through trochlea and inserts onto the superoposterior aspect of the eye.
Intorts the eye
Depresses the eye
Slightly abducts the eye
Innervated by the Trochlear nerve
Origin, insertion, action and innervation of Inferior Oblique muscle.
Arise from the anteromedial surface of the floor of the orbit and inserts onto the inferoposterior aspect of the eye.
Extorts the eye
Elevates
Slightly abducts
Innervated by the Oculumotor nerve
What is strabismus?
When the resting position of eyeball deviates and are not balanced.
In what position is the abnormal eye held?
What muscular action on the eyeball is no longer acting on the eye?
Is there one muscle that is normally responsible for this action on the eye?
What CN innervates it?
Adduction
Abduction is not possible
Lateral rectus
Abducens nerve
In what position is the abnormal eye held?
What muscular action on the eyeball is no longer acting on the eye?
Is there one muscle that is normally responsible for this action on the eye?
What CN innervates it?
Adducted, elevated and externally rotated
Abduction, depression and internal rotation
Superior oblique
Trochlear nerve
Explain in simple words how a clinical examination of the eye movements is done.
In the form of an H.
Why is an eye examination simply performed like a ‘+’?
Because elevation and depression in the midline involves two muscles each and will not isolate the muscle action as is required.
What muscles does this involve?
Superior rectus
Inferior oblique
What muscles does this involve?
Superior oblique
Inferior rectus
Given that the nose will be found on the right hand side.
What muscle does each end test?
Causes of cranial nerve palsies of CN III, CN IV and CN VI.
Raised intracranial pressure like intracranial haemorrhage or tumour.
Most commonly however due to vascular disease from e.g. diabetes or hypertension.
In CN III lesions, how will this present upon clinical examination?
Ptosis
Abducted, depressed and extorted eye.
Pupil dilation
How can you differentiate between a compressive lesion and vasculopathic lesion on CN III?
Vasculopathic lesion will be pupil sparing
In a compressive lesion on CN III the parasympathetics that run on the periphery of CN III will also be involved and therefore the pupil will involved and dilated.
Causes of CN III palsy.
Vasculopathic (most common)
Tumour/Haemorrhage etc…
Aneurysm
Clinical presentation of CN IV palsy.
Extortion, elevation and adduction of eyeball.
Patient may complain about diplopia but may tilt their head in order to correct it.
Worsening diplopia on downward vertical gaze.
The patient may report that there is worsening diplopia descending stairs or reading for example.
Causes of CN IV palsy.
Vasculopathic
Tumour
Congenital trauma
How will a CN VI palsy clinically present?
Inability to abduct the eye.
Diplopia made worse on horizontal gaze.
Causes of CN VI palsy.
Vasculopathic
Tumour
Cranial pressure
What is the most common cause of CN III, IV and VI palsy?
Vasculopathic lesion.
A lot of patients will be otherwise asymptomatic apart from the palsy of the given nerve.
The lesion will usually resolve itself within a few months.
What signs might suggest a more concerning cause of a cranial nerve palsy?
Headache and/or vomiting associated with raised ICP
Recent head injury
Presence of pupil involvment in CN III lesions
