17 - Eye Movements Flashcards
What are the different extrinsic and intrinsic muscles of the eye?
- Muscles of the eyelid: LPS and OO
- Extra ocular muscles that move eyeball
- Muscles of iris to control pupil
- Muscles of ciliary body to control lens thickness
Label the following extra-ocular muscles of the eye.
All attach to sclera of the eye and recti come from common tendinous origin around optic canal
LPS on top of superior rectus
Why do we need binocular vision?
- Allows us to have depth perception. Two images get sent to visual cortex and fused to be seen as one
- Can get depth diplopia if visual axes malaligned
What is the nerve innervation to the extra occular muscles?
LR6SO4R3
What muscles are allowing this movement of the eyes?
Lateral (6) and medial (3) rectus
What action does superior rectus have on the eye if at primary resting gaze?
- SR inserts into superior anterolateral eye
- Elevates
- Adducts
- Slightly intorts
What action does inferior rectus have from primary resting gaze?
- IR inserts on anteroinferior surface of eye
- Depress
- Adducts
- Extorts
What action does superior oblique have?
- Functional pull from trochlea
- Intort
- Depress
- Abduct
What action does inferior oblique have?
- Extort
- Elevate
- Abduct
What is the nerve palsy here?
- Issue with abduction as adduction so lateral rectus
- CN 6
What is the nerve palsy here?
- Right eye held elevated, adducted and externally torted as head tilt so superior oblique lost
- CN 4 issue
How would you test the extra-occular muscles of the eye?
- Move eye medially or laterally before elevating and depressing
- H
What can cause a cranial nerve palsy?
- Raised ICP e.g tumour or haemorraghe
- Vascular diease like hypertension or diabetes
How would an occulomotor cranial nerve palsy present?
- Pupil spared if vascular but if compressive dilated pupil
- Ptosis
- Down and out
How would a trochlear cranial nerve palsy present?
- Loss of SO so elevation, extorted and adducted with head tilt to compensate
- Worsening diplopia when looking down and medially e.g down stairs or book
How would an abducens cranial nerve palsy present?
- Loss of lateral rectus so cannot abduct eye on affected side
- Diplopia worse on horizonal gaze
How can you workout the underlying cause of a cranial nerve palsy affecting the eyes?
If somebody had an eye test and got the results 6/9 and 6/12, which is better?
- 6 means distance from the Snellen chart
- 9 is better as it is the lowest line you can read
How do we perform a clinical examination of the eye?
How do we measure visual field and visual acuity?
Acuity: snellen chart and near vision by reading newspaper
Field: test one eye at a time. loss in one eye is issue with optic nerve, bitemporal hemianopia is ?pituitary tumour
What reflexes of the eye are you checking on an eye examination?
- Accomodation
- Light (consensual and direct)
How do we perform fundoscopy and what are we looking for?
- Dim lights and give mydriatics
- Tell patient to focus on point in distance and start far and work in
- Look for red reflex
- Inspect optic disc
How does aqueous humour drain?
Why is it not possible to lose a contact behind the eye?
What does papilloedema look like on fundoscopy?
The optic disc appears swollen, its margins blurred and with increasing severity the entire nerve head may appear elevated (protrusion into the globe) with the borders completely obscured.
What is the difference between papilloedema and optic disc cupping?
What is presbyopia?
What are the direct and consensual pupillary light reflexes?
What is the arterial supply to the retina and what would happen if this artery got blocked?
What is the most likely organism causing otitis externa?
- P.Aeruginosa
- Staph Aureus
