The document discusses the importance of extraocular eye movements for visual range and image clarity, detailing the function of extraocular muscles and their complex actions based on eyeball positions. It categorizes eye movements into involuntary (tremors, drifts, flicks) and voluntary (pursuits, saccades), and explains concepts such as duction, version, and vergence. Additionally, it outlines control mechanisms for eye movements at the cortex and brainstem levels.

1. Extraocular Eye
Movements
Dr Zaid Azhar

2. Need for eye movement
• We need our
eyes to
increase the
visual range
that can be
covered

3. Need for eye movement
• Eye movements
bring the image
onto the fovea.
• Receptors for
vision located on
back of eyeball, on
the retina.

4. Extraocular Muscles (EOM)

6. Extraocular Muscles

7. Extraocular Muscles

8. Extraocular Muscles

9. Muscle innervation
LR6 SO4 O3

10. Action of extraocular muscles
• Actions are determined by position of eye ball
• Primary Position: Straight ahead
• Secondary Positions: Left, Right, Up, Down
• Tertiary positions: Oblique
• MUSCLES, THUS, HAVE COMPLEX ACTIONS

11. Action of extraocular muscles

12. Action of extraocular muscles

13. Action of extraocular muscles

14. Types of eye movements
Involuntary
• Tremors (Help keep image refreshed)
• Drifts (Help keep image refreshed)
• Flicks (Help eyes move so that image fall on fovea again)
Voluntary
• Pursuits (Slow movements to ‘track’ objects)
• Saccades (Fast movements to ‘jump’ to objects)

15. Types of voluntary eye movements
Pursuits
• To ‘follow’ objects
• What we usually test
Saccades
• To ‘rapidly’ shift gaze to an object of interest

16. Types of voluntary eye movements
Duction
• Examining movement of one eye (monocular)
• Remember it is not possible to move one eye alone!
Version
• Movements of both eyes in the same direction
(binocular)
Vergence
• Movements of both eyes in opposite direction
(binocular)

17. Ductions

18. Vergence

19. Versions

20. Horizontal conjugate gaze

21. Rule 1
• Both eyes must move together
• Muscles in both eyes are thus paired
• Paired muscles (yoke muscles) help move the eye in
a given direction.
• They both thus get similar stimulatory signals from
the brain (herrings law)

22. Rule 2
• Muscles in one eye have an agonist- antagonist
relationship
• The horizontal rectii form one set
• The vertical rectii/ obliques for the other set
• When one muscle in the set contract the other
must relax (sherrington’s law)

23. Versions
INFRA VERSION
DEXTRO
VERSION
LEVO
VERSION
SUPRA VERSION
One eye
follows
the other
Agonist
Pairs in
both eyes
These are
called
‘Yoke’
muscles
Both get
equal
impulses
HERING’S LAW

24. Versions
INFRA VERSION
DEXTRO
VERSION
LEVO
VERSION
SUPRA VERSION
The
antagonist
muscles to
yokes…
… are
inhibited…
…to allow
for
optimal
actions…
…of yoke
muscles
SHERRINGTON’S LAW

25. Horizontal conjugate gaze

26. Higher control of eye movements
Cortex
• Primary eye field in
Area 8 controls
voluntary saccadic
conjugate movements
• Occipital eye field in
Area 18 and 19 controls
smooth pursuit
movements

27. Higher control of eye movements
Brainstem
• Pontine centers
control involuntary
saccadic conjugate
movements
• Medial Longitudinal
Fasciculus connects
nuclei of CN III, CN IV
and CN VI