EOMs Flashcards
Which types of eye movements (ductions, versions, vergences) are monocular, and which are binocular?
monocular - ductions
binocular - versions (conjugate) and vergences (disjunctive)
Dextroversion means?
right gaze (both eyes look right)
Levoversion means?
left gaze (both eyes look left)
Supravergence means?
one eye looks up, the other doesn’t move
Infravergence means?
one eye looks down, the other doesn’t move
What does tertiary position of gaze mean?
the eyes are rotated around both vertical and horizontal axes (looking both up/down and left/right)
What is the origin of the rectus muscles?
SR: Common tendinous ring + ON sheath
MR: CTR + ON sheath
LR: CTR + spina recta lateralis (on the greater wing of sphenoid bone)
IR: CTR only
What is the spiral of Tillaux
insertions of the rectus muscles on the sclera, the MR insertion is closest to the limbus, then IR, LR and furthest is the SR insertion
What is the largest and thickest EOM?
Medial rectus due to so much converging
How many degrees is the SR insertion compared to the sagittal axis?
23 degrees (roughly half of the 45-degree orbit) IR is similar, parallel to SR
What are the actions of the SR?
primary - elevation
secondary - adduction, intorsion
What are the actions of the IR?
primary - depression
secondary - adduction, extorsion
What is the longest and thinnest EOM?
Superior oblique
What is the origin of the SO muscle?
anatomic origin is the lesser wing of the sphenoid bone, medial to the optic canal, and then the trochlea is considered the physiological origin
What angle does the SO muscle make with the sagittal axis?
55 degrees
What are the actions of the SO muscle?
primary - intorsion
secondary - depression, abduction
Which is the shortest EOM?
Inferior oblique muscle
What is the origin of the IO muscle?
on maxillary bone, posterior to the inferior medial rim
What angle does the IO muscle make with the sagittal axis?
51 degrees
What are the actions of the IO muscle?
primary - extorsion
secondary - elevation, abduction
What is Sherrington’s Law of Reciprocal Innervation?
contraction of a muscle is accompanied by a simultaneous and proportional relaxation of the antagonist
What is Hering’s Law of Equal Innervation?
the innervation to the muscles of the two eyes is equal and simultaneous, thus the movements of the two eyes are normally symmetric (binocular movements)
What is the origin of the levator palpebrae superioris (LPS)?
the lesser wing of the sphenoid, anterior/superior to the optic canal (muscle sheath blends with the sheath of SR)
What are frontal eye fields and where are they located in the brain?
Frontal eye fields are located in the frontal cortex and are involved in voluntary and reflex movements, etc., it communicates with EOMs via the paramedian pontine reticular formation (PPRF)
Where in the brain does visual processing occur?
striate cortex located in the occipital cortex
Which of the superior vs inferior colliculus receives visual inputs from the LGN?
superior colliculus
What eye movements does the PPRF primarily coordinate?
coordination of eye movements, particularly horizontal movements
What is the medial longitudinal fasciculus (MLF)?
coordinates eye movements, connecting CNVIII, CNIII, CNIV, and CNVI, also receiving input from the cerebellum and/or superior colliculus.
the rostral interstitial nucleus of the MLF (riMLF) is primarily in the midbrain