The eye muscles Flashcards
What do dextro and levo mean?
dextro = right and levo= left
Intorsion and extorsion?
tilt head to one side and eye will go towards the nose and one away
Are the EOM’s attached along the orbital or optical axis?
orbital
What is the relation of the orbital axis to the optical axis?
at angles to eachother
What is the affect of the muscles being attached along the orbital axis?
pull eye at an angle and hence have more than one movement/action of the eye
Are the obliques attached to the anterior or posterior part of the sclera?
posterior
Does the anterior part of the eye move in the same or opposite direction of that the oblique has pulled it?
opposite
What 3 EOM’s have only 1 action on the eyeball?
the medial and lateral recti
What do the lateral and medial recti do to the eyeball?
medial - adducts lateral - abducts
superior rectus actions
elevation - LR
intorsion - MR
inferior rectus actions
depression - LR
extorsion - MR
superior oblique action
intorsion - LR
depression - MR
inferior oblique action
extorsion - LR
elevation - MR
obliques elevate/depress when eye is…
recti elevate/depress when eye is…
adducted
abducted
strabismus
misalignment of the eyes - squint
Esotropia
manifest convergent squint
Exotropia
manifest divergent squint
2 functional consequences of squint
amblyopia - lazy eye
diplopia - double vision
Amblyopia/lazy eye - how does it work?
brain suppresses image of one eye leading to poor vision with no pathology
What type of squints are diplopia usually seen with?
nerve palsy
pupillary reaction to increased illumination
parasympathetic - pupils constrict
pupillary reaction to decreased illumination
sympathetic - pupils dilate
How would you test pupillary reflex? (brief)
use a pen torch in a dimly lit room on one eye which should constrict both eyes
move torch to other eye - both sides should still be constricted
Afferent pathway for light reflex
optic nerve -> optic chiasma -> optic tract -> midbrain ( CN 3 nucleus) -> EWN for parasympathetic -> nerve fibres for pupillary reflex -> midbrain
Do pupillary reflex fibres go to LGB?
NO - EWN
efferent pathway for light reflex
EWN -> preganglionic parasympathetic fibres synapse in ciliary ganglion and send short ciliary fibres to constrictor pupillae –> pupillary constriction on both sides
Aniscoria
pupils of different sizes
What is a condition that aniscoria may be found?
Horner’s syndrome
3 reasons for pupils looking normal but reacting abnormally to light?
retinal diseases
optic nerve disease
CN 3 disease
retinal disease examples
detachment, dystrophy, degeneration
optic nerve neuritis disease example
MS
If there is an absent parasympathetic pupillary reflex to light what can this mean?
cerebral artery aneurysm
diabetes would have no damage to parasympathetic fibres
Horners aniscoria - damage to sympathetic or parasympathetic fibres?
sympathetic - dilation
3 signs of horner’s anisocoria
miosis - constricted pupil
anhidrosis - sweating on affected side
ptosis - drooping of eyelid
What region of the vertebra is sympathetic outflow?
thoraco-lumbar
In the head and neck how to postganglionic sympathetic fibres travel?
along with blood vessels
