Eye muscles and movement Flashcards
What movements do fick’s axis make
X - up and down
Z- left and right
Y - intorsion and extorsion
What are the insertion of recti muscles from the limbus
MR - 5.5
IR - 6.5
LR - 6.9
SR - 7.7
Actions of recti muscles
Superior Intort
Superiors Rectus ADDucts
Inferior rectus ABDucts
Superior oblique movements
reading muscle
- ADDUCTS
- Intorsion
- depresses
What degree to isolate:
SO/IO
Primary degree is smaller than secondary degree
Primary movement (intorsion/extorsion)
39 degrees aBduction (PB)
Secondary movement (elevation/depression)
51 degrees aDduction (SD)
What degree to isolate:
SR/IR
Primary degree is smaller than secondary degre
Primary movement
(elevation/depression)
23 degrees aBduction (PB)
Secondary movement (intorsion/extorsion)
67 degrees aDduction (SD)
What is Hering’s law?
Equal innervation to yoked muscle pairs
Produce binocular eye movement of equal distance, speed and direction
What is Sherrington’s law
unequal innervation to antagonsitic muscles
What is strabismus + tropia vs phoria
Hyper vs Hypo vs eso vs exo
strabismus - abnormality of eye movement
Tropia - If abnormality arises from end of the bed or a simple cover test
Phoria - If abnormality arises from an alternate cover test
What is a quick test to evaluate severity of strabismus
Hischberg’s test ( Corneal light reflex test)
for every 1mm of de-centration = 15 degrees of tropia or 7/7.5 prism diptres
what are A and V patterns
Applies to both esotropia or exotropia based on primary postion
A pattern - angle of deviation is smaller in upgaze but bigger in downgaze
V pattern - angle of deviation is bigger in upgaze than in downgaze
What is the A and V pattern treatment
MALE
Medial rectus towards Apex
Lateral rectus towards END
How does CN III palsy present
down and out
due to unopposed pulling of superior oblique (down) and lateral rectus (out)
Pupillary involvment rule in CN III palsy?
Pupil dilation (pressure on parasympathetic fibres) is mainly caused by surgical causes (i.e. aneurysm)
Pupil sparing palsy can be due to surgical or non-surgical causes
CN IV Palsy - how does it present?
Superior oblique affected (trochlear nerve palsy)
Head tilt, chin down , head turned away from side affected - in unilateral palsy
Eye is extorted, elevated and abducted. Head movments compensates for this
