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Exam 1_ EOMs
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- NUR 240 EXAM 2 Practice Questions.
Exam of 16 pages for the course NUR 240 EXAM 2 Practice Questions. at NUR 240 EXAM 2 Practice Questions. (Exam 1_ EOMs)
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Exam 1: EOMs3 axes - ANS-eyeball rotates about 3 axes
horizontal = x
vertical = y
sagittal (anterior-posterior: AP)= z
agonist - ANS-muscle that moves an eye in a give direction
angles in primary gaze
(how to tell what the H test is looking for) - ANS-in primary gaze the axis of the SR and
IR forms an angle of 23 degrees with the optic axis (AP axis)
SR = eye adducts 23 degrees so that the muscle's axis is lined up with AP axis
- action of adduction is cancelled and its action of elevation increases
- when eye is abducted the SR becomes only an elevator
IR = eye adducts 23 degrees so that the muscle axis is lined up with the AP axis of the
eye
- action of adduction is cancelled and its action of depression increases
- eye is abducted so IR becomes a depressor only
antagonist - ANS-muscle that moves the same eye in the *opposite* direction of the
agonist
Assessing EOMs clinically - ANS-each muscle can have many actions
we need to position eye in a way that a single action off the muscle predominates
*physiologic H* = clinical test to evaluate EOMs
start with transiluminator in primary position and move light in H pattern
align the optic axis (AP axis - Z axis) with the axis of the muscle you want to test
,muscle becomes a pure elevator or pure depressor for SR, SO, IR, IO
closer muscle to limbus - ANS-the closer to the limbus a muscle attaches, the stronger
is its pull on the eyeball
medial rectus muscles are used to bring the eyes inwards toward the nose during near
work so they lie closest to limbus to be most effective
CN 3 palsy - ANS-eye is deviated in the direction of action of the EOMs that are
unaffected
eye is positioned down and out due to unopposed actions of the LR and SO
Common tendinous ring (annulus of zinn) - ANS-- oval connective tissue ring made of
thickened periorbita
- located at the apex of the orbit
- it surrounds the optic canal and the central portion of the superior orbital fissure
Origins here:
- SR
- IR
- MR
- LR
(all rectus muscles)
Duction - ANS-movement of ONE eye
MONOCULAR eye movements
movements that each eye can do alone
dural sheath of the optic nerve - ANS-Origins here:
- SR
- MR
(they also have origins in common tendinous ring)
, important b/c:
optic neuritis is an inflammatory response directed against the optic nerve's myelin
which leads to demyelination and axon loss
this leads to ganglion cell death and decreased visual acuity
inflammation also effects the meninges (dura, arachnoid, and pia) that surround the
optic nerve
Enucleation of eyeball - ANS-removal of eyeball
cut optic nerve and detach EOMs
tenon's capsule should be preserved to serve as socket for prosthetic eye
reasons for enucleation:
- blind, painful eye
- intraocular malignant tumomrs
- blind, deformed eye
EOMs - ANS-there are 6 EOMs used to move the eye in all directions
clinically important for many reasons
- strabismus
- movements are indicators of CN function
- they are affected in disease states (i.e, diabetes, thyroid eye disease and myasthenia
gravis)
Esotropia - ANS-one or both eyes is turned towards the nose
Evisceration - ANS-remove cornea, uveal layer and retina but leave sclera, optic nerve
and EOMs intact
place ocular implant into scleral shell
allows ocular motility to be much better - less chance of enophthalmos
Exenteration - ANS-remove all the orbital contents so only the bone remains
more difficult to maintain cosmetically
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