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26 Cards in this Set

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OD HT // OS fixing
OD fixing // OS Hypo
Right hypertropia (RHT)
Is comitancy common in a vertical deviation?
(T/F) It is easier to fuse vertically than horizontally.
False - to the contrary
(T/F) Vertical deviations generally occur in isolation.
False - generally have horizontal and torsional components
Which EOMs are responsible for vertical actions?
What is the
a) action of the SO muscle?
b) field of action of the SO muscle?
a) incyclotorsion, depression, abduction
b) down, left or down, right
Use muscle stars & |_ _|
What is a yoke muscle?
movement of a single muscle is aided by a "partner" in the other eye - the yoke muscle
What is the yoke muscle of:

a) R MR
b) L SO
c) R SR
a) L LR
b) R IR
c) L IO
A child is unable to elevate his eyes. Which head posture will he adopt?
head/chin upward
What is the result of a bilateral Inferior Oblique Overaction?
crossed hyper - RHT worse on left gaze, LHT worse on right gaze
A patient who has LHT worse on right gaze, RHT worse on left gaze.
crossed hyper - IOOA or SO underaction
In relation to IOOA, define the meaning of primary vs secondary over/underaction
Primary: IO overacts
Secondary: SO underacts, causing IO to overact
What pattern does IOOA cause? Why?
V pattern

- more XT on upgaze
- straight in primary
- ET in downgaze

* IO o/a, SO u/a
What pattern does SOOA cause? Why?
A pattern

- ET on upgaze
- straight in primary
- XT downgaze

* SO o/a, IO u/a
Describe the stages of paretic muscle sequelae.
1. underaction of the paralyzed muscle
2. overaction of the ipsilateral antagonist
3. overaction of the contralateral agonist
4. underaction of the contralateral antagonist [INHIBITIONAL PALSY]
What is the reason that we see incomitance in vertical deviations?
paretic muscle sequelae
(T/F) In a paresis, the patient can adduct better than he/she can diverge.
In general, true - ductions better than versions
In which circumstance(s) is the 3-step head tilt test not reliable?
- previous surgery
- muscle restriction
- bilateral paresis
- longstanding problem
When is the 3 step head tilt test used?
To identify which muscle is paralyzed.
Why are SO muscle palsies so common?
- SO innervation comes from Trochlear (IV) cranial nerve
- CN IV exits dorsally from brain (only nerve to do this)
- CN IV has longest intercranial course

this makes CN IV more susceptible to trauma.
What adverse effects will a patient have with a CN IV palsy?
- diplopia - can be vertical, oblique, or torsional
- hypertropia
- excyclotorsion
- eso
(T/F) Most SO palsies are traumatically induced.
True - CN IV "trauma" nerve

A patient was smacked lightly on the back of the head, resulting in a slight hyper/eso in one eye.
trauma induced CN IV palsy - most likely secondary to a preexisting condition
How can you distinguish a bilateral muscle palsy? (Ex. bilateral SO)
- crossed hyper
- vertical in pp may not be present since bilaterally (if ~same amount of deviation) they will cancel each other
- torsion greater than 12 degrees
- history of head trauma
What is a masked bilateral SO palsy?
SO palsy originally thought to be unilateral, but post-op the component in the other eye (which was there in the first place) has now been brought out
What are some factors which could differentiate a longstanding (congenital) SOP from an acquired one?
- facial asymmetry
- longstanding head tilt - patient thinks head is straight - pictures
- stretched vertical fusional amplitudes - normal ~ 2-3
- congenital may suppress diplopia, while acquired will be very aware of it