Page 195 - Edited - Webster HEAD AND NECK - part 1

EYE MOVEMENTS & NERVES
HN 161

(A) THE PRIMARY POSITION: looking into distance. Eyes do NOT diverge beyond this position.
NOTICE relations of lid
margins to edge of iris: lid
RETRACTION beyond this
(as in thyrotoxicosis) results in
“STARING GAZE”.
ADDUCT ADDUCT If convergence is for
(B) CONVERGENCE. accommodation (looking

CrN III CrN III at near object) the pupils
temporarily constrict.
(C) CONJUGATE LATERAL GAZE
ADDUCT ABDUCT ABDUCT ADDUCT

CrN III CrN VI
(i) to left. CrN VI CrN III (ii) to right.

CrN III
CrN III
(D) ELEVATION OF
GAZE NOTICE the movements of the
upper lid: elevation by CrN III/lev.
pal sup. m. The absence or
sluggishness of these lid
(E) DEPRESSION OF movements is abnormal, & occurs
GAZE
in e.g. thyrotoxicosis,

CrN III CrN III
(CrN IV) (CrN IV)
myasthenia gravis.
(F) SUMMARY OF RELATIONSHIP BETWEEN CRANIAL NERVES & EYE MOVEMENTS

ABDUCT VS ADDUCT
RIGHT EYE.
L/T M/N
L/T = lateral rotation (1) L/T M/N (4)
temporal deviation
abduction ALL MOVEMENTS
(CrN VI) CrN III
WITHIN THE BOX
M/N = medial rotation ARE CrN III
nasal deviation E (OCULOMOTOR
adduction L/T M/N
(2) L/T M/N N.); CN VI
D = depression (5) (ABducent N.) AB
(downward gaze) D ducts the eye; CrN
(CrN IV) CrN III IV (TROCHLEAR)
E = elevation (upward Supplies the muscle
gaze) E with a pulley
L/T L/T E (TROCHLEA).fe
(3) M/N M/N
(6)
D
CrN III CrN III
ARRANGED AS OPPOSING PAIRS:

(1) LATERAL RECTUS (VI) (4) MEDIAL RECTUS (III)

(2) SUPERIOR OBLIQUE (IV) (5) SUPERIOR RECTUS (III)
(3) INFERIOR OBLIQUE (III) (6) INFERIOR RECTUS (III)

THUS, EYE MOVEMENTS ARE PRODUCED BY BALANCING ACTIONS OF
OPPOSING MUSCLES.
KEW.