This document provides information about Ankit S. Varshney, an optometrist in India, and discusses the extraocular muscles. It begins by introducing the six extraocular muscles that control eye movement. It then covers basic terminology related to eye movement including the axes of Fick and muscle planes. The document discusses each of the six muscles in detail, including their actions and innervation. It also covers physiology of ocular movement, including types like duction, version, vergence, and the roles of agonist, antagonist, and synergist muscles. Finally, it discusses clinical applications of ocular muscle function and Hering's law of equal innervation.

1. Optom. Ankit S. Varshney
B.Optom,M.Optom,Ph.D.in Optometry(pursuing)Fellowof IACLE(Aus.),Fellowof ASCO(Mum.)
Prof.at (Shree BharatimaiyaCollegeof Optometry& Physiotherapy, Surat)
Life Member of Indian Optometric Association (IOA)
Associate Member of Association of Schools and Colleges of Optometry(ASCO)
Member of Optometry Council of India(OCI)
Educator Member of International Association of Contact lense Educators (Australia)(IACLE)
Mail id: ankitsvarshney@yahoo.com
Whatsapp no. +918155955820
EXTRA OCULAR MUSCLES

2. Introduction:
 The eyes are rotated by the action of six extraocular muscles,
which allows rotations in horizontal, vertical and torsional
directions.
 These are :-
1. Medial Rectus
2. Lateral Rectus
3. Superior Rectus
4. Inferior Rectus
5. Superior Oblique
6. Inferior Oblique
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6. Basic Terminology
 Axes of FICK
 Muscle Plane
 Axis of Rotation
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Y-axis
Z-axis X-axis
MP
AR

7.  The theoretical center of rotation of the eye is at the
intersection of the three principal axes of Fick, around
which the eye performs rotatory movement
 The X-axis crosses the eye horizontally; the Y-axis passes
through the center of the pupil (through the ‘y’ sutures of
the lens); and the Z-axis crosses the eye vertically.
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8.  The visual axis is a straight line that can be drawn from
a distant object of regard to the fovea.
 In the normal eye, the visual axis passes through the
apex of the cornea, the center of the pupil, and the
thickest anterior-posterior part of the lens.
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9. AXES OF FICK
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10.  The horizontal plane is a primary plane
of action.
 The horizontal line going through the cornea
represents the visual axis .
 The vertical line with the arrow at the top
represents the vertical axis. As the eye turns
around the vertical axis, the visual axis
sweeps along the horizontal plane.
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11.  The vertical plane is the second of the
primary planes of action.
 The line going through the cornea
represents the visual axis .
 The horizontal line with the
arrow represents the horizontal axis. As the
eye turns around the horizontal axis, the
visual axis sweeps along the vertical plane.
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12.  The third plane of action are:-
1. Intortion and extortion refer to rotation around the
visual axis,
 Intortion refers to a nasal rotation from the 12
o'clock position.
 Extortion refers to a temporal rotation from the 12
o'clock position.
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13.  The MR and the LR each have only one "action".
 These actions occur only along the horizontal plane.
 The other EOMs are called cyclovertical muscles.
 Each of these muscles has more than one action. They
act in the vertical plane as well as the horizontal plane,
and they also intort or extort the globe.
 These muscles each have a primary action (1°), a
secondary action (2°), and a tertiary action (3°).
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14. Medial Rectus
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Z-axis
AR
MP

15. The MR is the strongest of the EOMs.
It has the most mass, and it has the most anterior insertion
into the globe (for greater leverage). It is used often to
converge the eyes into near (reading) gaze.
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16. Lateral Rectus
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Y-axis
Z-axis
MP
AR

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18. Superior Rectus
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Y-axis
MP
X-axis
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Nasal
Temporal
AR

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22. Inferior Rectus
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Y-axis
MP
X-axis
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Nasal
Temporal
AR

23. - PULL OF SUPERIOR & INFERIOR RECTUS AT
ANGLE WITH LINE OF SIGHT
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25. Superior Oblique
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Y-axis
MP
X-axis
Nasal
Temporal
AR
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28. Inferior Oblique
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Y-axis
MP
X-axis
Nasal
Temporal
AR
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33. Physiology of ocular movement
1. Duction :
 The movement of one eye (monocular) by itself is called a duction.
 Movement of the eye nasally is adduction;
 Temporal movement is abduction.
 Elevation is termed sursumduction (supraduction)
 Depression is termed deorsumduction (infraduction),
 Incycloduction (intorsion) is nasal rotation of the vertical meridian
 Excycloduction (extorsion) is temporal rotation of the vertical meridian.
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34. 2. Versions
 The movement of the two eyes in the same
direction is termed a version.
 When both eyes look to the right, the
movement is called dextroversion.
 Left gaze is called levoversion.
 Both eyes in upgaze is termed supraversion.
 Downgaze is called infraversion.
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35. 3. Vergences
 They are the movements of the eyes in opposite
directions.
 Convergence is movement of both eyes nasally, and
Divergence is movement of both eyes temporally.
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36. 4. Saccades
Saccadic eye movements are very fast jumps
from one eye position to another. The velocity
of saccades can be as large as 1000 deg/sec.
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37. 5. Pursuit movements
 Smooth pursuit movements are just as their
name implies. The eyes move smoothly instead of
in jumps. They are called pursuit because this type
of eye movement is made when the eyes follow an
object.
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38. 6. Agonist
 It refers to particular EOM producing a specific
ocular movement.
 When the lateral rectus (LR) contracts, the eye
moves temporally (abduction). The LR is the
agonist muscle for the action of abduction.
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39. 7. Antagonists
 When the LR muscle contracts, the MR muscle must
relax ,
 Therefore, the MR is the antagonist of the LR and
the antagonist of the action of abduction.
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40. 8 . Synergist
 Two muscles moving in same direction are called
synergists.
 SR & IO muscles of same eye act for elevation
movement
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Muscle pair Function
SR & IO Elevation
IR & SO Depression
SR & SO Intortion
IO & IR Extortion

41. 9. Yoke muscles
 A pair of muscles which contract simultaneously during
version movement.
 The LR of the right eye and the MR of the left eye for
dextroversion are called yoke muscles.
 Moves the eye in the same/opposite direction
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42. THE NINE DIAGNOSTIC POSITIONS OF
GAZE
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1. A nine position of gaze
2. One primary position
3. Four secondary &
4. Four tertiary position

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44. Laws of Ocular motility
1) Hering’s law of equal innervation
2) Sherrington’s law of reciprocal
innervation
CLINICAL APPLICATIONS :-
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45. WHY?
 Moving the eyes enables the field of view to
increase and allows the Fovea, the small region of
good vision, to move.
 Thus by this mechanisms we can lock on to track
the target, maintain foveal fixation and binocular
vision.
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46. THANK U
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