PCO2-Hirschberg test and EOMs
test used to id strabismus when other precise methods cannot be used - ANS-hirshberg
test
monocular hirsberg test - ANS-have pt fix at the light and occlude OS and determine the
position of the reflex of OD; this is angle kappa/lambda (is the angle subtended by the
visual and anatomical axes)
binocular - ANS-remove occluder and observe location of reflex in both eyes; compare
both fixating vs only one -- if reflexes are the same in each eye there is no strabismus or
ortho
when the corneal light reflex (CLR) is nasal to the center of the pupil it is assigned? -
ANS-+ value
when CLR is temporal to the center of the pupil it is assigned - ANS-- value
test performed by penlight held directly in front of pt and corneal light reflexes are
observed; an asymmetry indicates the direction and magnitude of an eye turn,
depending upon the position of the reflexes - ANS-hirshberg test
1mm of corneal reflex displacement deviation is = to - ANS-22 delta or 12degrees
if eye is outward (exo) you want it to move inward therefore you use? - ANS-base in
an inward eye (eso) you want to move outward so you use - ANS-base out
tracking mechanisms that maintain foveal fixation, binocular vision, and lock on to track
a target - ANS-EOM
special characteristics of EOMs - ANS-sense nerve supply, finely tuned
more dense blood supply
faster and more resistant to fatigue (due to unique blend of fast and slow but sustained
muscle fibers)
the movement of one eye by itself - ANS-duction
the movement of two eyes in the same direction - ANS-version
, monocular rotations of the eye towards the nose - ANS-ADDuction
monocular rotation of the eye toward the temple - ANS-ABDuction
a nasal rotation from the 12 o clock position - ANS-intortion
a temporal rotation from the 12 o clock position - ANS-extortion
both eyes in upgaze - ANS-supraversion
both eyes in downgaze - ANS-infraversion
when both eyes look to the right - ANS-dextroversion
when both look to the left - ANS-levoversion
eyes move in the opposite direction simultaneously - ANS-vergences
(convergence/divergence)
the four EOM muscles arise from the tendinous ring called - ANS-annulus of zinn
(common tendinous ring)
2 tendons - ANS-upper (lockwood)
lower (zinn)
arises from the body of the sphenoid bone and gives origin to part of the medial and
lateral recti and all of the superior rectus muscle - ANS-upper tendon (lockwood)
is attached to the inferior root of the lesser wing of the sphenoid and gives origin to part
of the medial and lateral rectus and all of the inferior - ANS-lower tendon (zinn)
the recti muscle passes through the tenon's capsule and inserts into the sclera (at
different distances from the cornea) - ANS-spiral of tillaux
t/f spiral of tillaux insertion pattern is a spiral with the medial rectus closest to the cornea
and the superior rectus furthest away. - ANS-true
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