Eye Muscles Flashcards
what are the uniocular terms of eye movements?
upwards= elevation, downwards= depression, away from the nose= abduction, towards the nose= adduction
what are the binocular terms of eye movements?
upwards= elevation, downwards= depression, right= dextroversion, left=levoversion, up and to the left= levoelevation, down and to the left= levodepression, up and to the right= dextroelevation, down and to the right= dextrodepression
what do intorsion and extorsion mean?
intorsion= top of eyeball rotates towards the nose and extorsion= top of eyeball rotates away from the nose
what are the actions of individual EOMs influenced by?
muscles are attaches along the orbital axis and not the optical axis and so pull on the eyeball at an angle and the oblique muscles are attached to the posterior part of the sclera and so pull the posterior part of the eyeball up/down so the anterior part moves in the opposite direction
what are the rules for testing the action of the EOMs?
the obliques elevate/depress when the eye is adducted and the SR and IR elevate/depress when the eye is abducted
what is strabismus?
a squint= misalignment of the eyes and can be esotropia= convergent squint or exotropia= divergent squint
what are the functional consequences of a squint?
amblyopia (lazy eye) where the brain suppresses the image of one eye leading to poor vision in that eye without any pathology (eye patches can correct in early years) and diplopia (double vision) usually due to sudden nerve palsies
what does pathology of innervation of intrinisic eye muscles cause?
pupillary abnormalities
how do you elicit the pupillary reflex?
start in dimly lit room (pupils dilated), pen torch in front of one eye and check for both pupils constricting and swing to the other side which should remain both pupils constricted
what is the pathway of the light reflex?
when light falls on the retina impulses travel along the optic nerve to the optic chiasma and to the optic tracts- fibres for pupillary reflex go to midbrain where the IIIn nucleus is situated and goes to both sides of the EWN which is why you get bilateral constriction of the pupils
describe the efferent limb of the light reflex.
from the EWN (part of the IIIn nucleus), the preganglionic parasympathetic pass through the IIIn into the orbit and synapse in the ciliary ganglion and to the constrictor papillae leading to pupillary constriction on both sides
what are possible pupil abnormalities?
different sizes of pupils= anisocoria eg Horner’s syndrome or pupils may look normal but react abnormally to light (abnormal light reflex)
what diseases could cause abnormal light reflexes?
diseases of the retina eg detachment/degenerations or dystrophies, diseases of the optic nerve eg optic neuritis (commonly seen in MS), diseases of the IIIn (efferent limb)
what happens in a IIIn palsy?
patient is unable to move the eye in various directions of gaze and sometimes the pupils are affected so check pupillary reflex- if absent suspect a cerebral artery aneurysm
