Session 8- Extraocular eye muscles, actions and testing Flashcards
what does binocular vision allow
wider field of vision and depth perception
what is conjugate eye movement
eyes need to coordinate and move together
what causes diplopia
misalignment of two visual axes image focuses on different area of each retina
-brain unable to fuse these see 2 separate images
what is diplopia
double vision
2 images seen can be displaced horizontal, vertical and diagonally
what are the for recti
superior
inferior
lateral
medial
what are the 2 obliques
superior
inferior
where do extra-ocular muscle attach
sclera
where do extraocular muscles riginate
apex of orbit except inferior oblique which arises from the floor of orbital cavity anteriorly
-the 4 recti originate from a common tendinous ring
what innervates the extra ocular muscles
LR6SO4
Lateral rectus- 6- abducens
Superior oblique- 4 -Trochlear
all remaining occulolotor
why do some muscles attach at an oblique angle
the muscles run in line with the axis of orbit
-confers several actions of movement on globe for some of the extra ocular muscles
which muscles have a single action on the eye
Medial rectus and lateral rectus
what movement is moving the eye medially
adduction
what movement is moving the eye laterally
abduction
what muscles adducts the eye
medial rectus
what muscle abducts the eye
lateral rectus
what is the action of superior rectus if starting from primary resting gaze
elevate
slightly adducts
slightly intorts
when is the superior rectus a more powerful elevator
when the eye is positioned laterally
where does superior rectus inserts
superior anteriolateral surface
where does IR attach
anteroinferior surface of globe
action of IR
depress
slightly adducts
slightly extort
when is IR a more powerful depressor
when the eye is positioned laterally
where does SO attach
passes through trochlea inserts into superior-posterior aspect of globe
SO action
intort
depress
when is the SO a more powerful depressor
when eye is positioned medially
where does IO attach
infero-posterior aspect of globe
action of IO
extort
elevate
slightly abduct
when is IO a more powerful elevator
when eye is positioned medially
which extra-ocular muscles have an action in elevating the eyeball
superior rectus
inferior oblique
which extra-ocular muscles have an action in depressing the eye ball
inferior rectus
superior oblique
which extra ocular muscles are stronger elevators and depressors of th eyeball when the eye is adducted
inferior oblique
superior obliquw
which extra-ocular muscles are stronger elevators and depressors of the eyeball when the eye is abducted oosition
superior and inferior rectus
strabismus
common in children - exact cause not always known
in adults- acquired due to pathology or disease -myasthenia gravis/ nerves supplying the muscles
cranial nerves can be affected
- vasculopathic
- physical compression
- raised intracranial pressure
how do we isolate elevaton and depression actions of SR/IO and IR/SO
move starting postion of eye laterally or medially first then test elevation and depression
what are the main elevators and depressors of the eye when the eyball is starting from the lateral position
recti muscles
superior - elevates
inferior- depreses
what muscles are the main elevators and depressors of the eye when the eye is in the medial position
IO - elevates
SO- depresses
what are the 2 qcquired causes of CN III palsy
vasculopathic lesions- pupil spared
compressive lesions -pupil involved
which extra ocular muscles does the trochlear nerve innervate
superior oblique muscle
-intorts, abducts and depresses
in what position is the eye held in a trochlear nerve lesion
extorted, slightly elevated and adducted
how is the extortion of the eye compensated in a trochlear nerve palsy
head tilt- this is because the eye is extorted and slightly elevated
what is the most likely cause for CN III, IV and VI
vasculopathic
What is the difference between periorbital cellulitis and orbital cellulitis?
Periorbital cellulitis confined to tissues superficial to orbital septum and tarsal plates.
Orbital cellulitis - result of an infection affecting fat and muscles posterior to orbital
septum, within the orbit but not involving the globe.
What are the three main types of conjunctivitis?
bacterial
viral
allergic
What is age-related macular degeneration?
Most common cause of blindness in the
UK. Degeneration of the macula is the key feature with changes usually bilateral. Two
forms of macular degeneration are dry and wet
What features will you see on the retina for central retinal artery occlusion?
Pale
retina, cherry red spot
Which test do you use to check colour vision?
ishihara chart
what is used to test visual acuoty
snellen chart
What is orbital cellulitis
red and swollen right upper and lower
eyelids. On examination, he had reduced visual acuity, mild proptosis, painful and reduced
ocular movements.
(usually caused by upper respiratory tract infection from the sinuses)
