Muscles of the Eye Flashcards
what is intorsion?
when the top of the eyeball rotates towards the nose
what is extortion?
when the top of the eyeball rotates away from the nose
what is the action of the MR?
adduction
what is the action of LR
abduction
what are the actions of the SR
elevation, adduction, intorsion
what are the actioins of IR
depression, adduction, extorsion
what are the actions of SO
intorsion, depression, abduction
what are the actions of IO
extortion, elevation and abduction
why do some muscles have more than one action?
The muscles are attached along the orbital axis and not the optical axis, so they pull on the eyeball at an angle
what is important about the attahcments of the oblique muscles?
they are attached to the posterior part of the sclera, so they pull the posterior part of the eyeball up/down and the anterior part moves in the opposite direction
what is the only elevator of the abducted eye?
SR
in the adducted position, does the recti or obliques elevate/depress the eye?
obliques
in the abducted position, does the recti or obliques elevate/depress the eye?
recti
what is esotropia?
manifest convergent squint
what is exotropia?
manifest divergent squint
what are the functional consequences of a squint?
amblyopia and diplopia
what is amblyopia?
(lazy eye) where brain supresses the image of one eye leading to poor vision in that eye without any pathology
what is diplopia?
(double vision) – usually occurs in squints occuring as a result of nerve palsies.
what type of innervation does increased illumination cause?
parasympathetic, both pupils constrict
what type of innervation does decreased illumination cause?
sympathetic, both pupils dilate
what is anisocoria?
when pupils may be different sizes
what are the causes of absent/abnormal pupillary reflex
Diseases of the retina – detachment/ degenerations or dystrophies
Diseases of the optic nerve – such as in optic neuritis (frequently seen in MS)
Diseases of the III cranial nerve
signs of horners syndrome
Anisocoria
Ptosis
Miosis
Anhidrosis