The document discusses the anatomy and function of the eyelids and eyebrows. It provides details on: 1. The main muscles that control eyelid opening and closing movements, including the levator palpebrae superioris muscle which is the primary elevator of the upper eyelid. 2. Hering's law which states that the levator muscles of the two eyelids act as yoke muscles and receive equal innervation. 3. The differences in movement between the upper and lower eyelids during opening and closing, with the lower lid moving horizontally and slightly before the upper lid during closing. 4. Types of blinking including spontaneous, reflex, and voluntary blinking and w

2. FARAH IFTIKHAR
Bsc(Hons) Optometry and Orthoptics
(Rawalpinidi Medical College Rawalpindi)
Gold medalist (RMC)
Bronze Medalist (UHS)

3. Lecture#2
Eyelids
and
Eyebrows

4. Eyebrows
• Coarse hairs overlie the superior orbital
margins
• Functions include
1.Shading of eye
2.Preventing perspiration from reaching the
eye

5. • Orbicularis muscle--depresses the
eyebrows
• Corrugator muscles--moves the eyebrows
medially

6. The Eyelids
• Protect the eye from injury and excessive
light by their closure
• assist in the distribution of tears over the
anterior surface of eyeball
• Maintains the integrity of corneal surface
• Maintain the proper position of globe
within the orbital contents

7. • Regulate the amount of light allowed to
enter the eye.
• Provide protection from airborne particles
• Coverage of the eyes during sleep

8. EYELID
MOVEMENT

9. • Lid opening
• Lid closure
• Blinking
• Voluntary blinking and winking
• Bell's Phenomenon

10. Lid Opening
• Upper Eyelid- Elevators
• Lower eyelid- Retractors

11. Upper lid Elevators
• Levator palperbrae superioris (the primary
elevator of the upper eyelid)
• The superior Palpebral muscle of Muller's
• Frontalis (acting as accessory elevator)
(Frontalis and Muller's become important
when the levator is defective)

13. Eyelid excrusion (during opening
movements
• In adults the upper eyelid is raised some
10-15mm from extreme downward gaze to
extreme upward gaze

14. Tone of levator Muscle
• In upward gaze, tone increases in both the
superior rectus muscle and the levator,
resulting in elevation of the visual axis and
elevation and retraction of the upper eyelid

16. Lower Lid retractors
• No true counterpart of the levator is
present and therefore the opening
movement depends upon several factors
• Traction exerted by the attachment of the
inferior rectus to the inferior tarsus
• Inferior palpebral muscle (identical to
Muller's muscle in the upper eyelid)

18. Dynamics of opening movement
• Opening of the upper eylid takes place
against gravity
• Opening movements of the upper and
lower eyelids begin in phase, although the
opening movement of lower eyelid is much
slower than that of the upper eyelid due to
lack of any direct muscular pull

19. • During opening Movement the upper lid
moves vertically upwards, while the lower
lid moves laterally in horizontal direction

20. Bilateral coordination and their
basis
• Opening movements of the eyelids are
bilateral,symmetrical,and identical in
direction and amplitude (although they
may be voluntarily inhibited on either side)
• So, the levator muscles of the two upper
eyelids behave as YOKE MUSCLES, in
that they act as a team or pair, obeys
Hering's law' of equal innervation

21. HERING'S LAW
• This implies that the innervational energy
reaching the one levator muscle is equal
to that reaching the other.

22. Reciprocal innervation pattern
• It exists between the levator muscle and
the orbicularis oculi muscle, i-e when
levator recieves maximum innervation
during opening,the orbicularis oculi
receives minimum innervation and vice
versa. Thus these muscles follow
'SHERRINGTON'S LAW' of reciprocal
innervation

23. Lid Closure

24. • Orbicularis oculi controls lid closure and is
supplied by the facial nerve

25. Upper lid versus lower lid during
closing movement
• Upper lid moves downwards (vertically) while the
lower lid moves medially (horizontally)
• Closing movement of both upper and lower
eyelids occur in phase, although the movement
of lower eyelid begins some 12-20 micro
seconds before the movement can be detected
in the upper eyelid
• Gravity does not play any role in downward
movement of upper eyelid during closing

26. Blinking
• Blinking can be devided into
• voluntary and
• Involuntary
• The involuntary blinks are further devided
into
• spontaneous
• Reflex blinks

27. Spontaneous blinking
• It is common form of blinking that occurs
without any obvious external stimulus or
voluntary willed efforts
• Spontaneous blinking is infrequent during
the first few months of life, yet the delicate
infant cornea does not suffer from dryness
• Average rate is 15 times per minute (12-
20)

28. • The blink rate is increased in
1.Extremely dry conditions
2.Strong air currents
3.Certain emotional stress situations
(surprise,anger or fight)
• A decreased blink rate occurs during times
of visual observations

29. • Present in blind, hence no retinal stimulus
is required
• No discontinuity of visual sensation during
blinking
• This helps the displacement of the tear
film to the lacrimal puncta which are
located on the medial side of lids

30. Course of events
• Relaxation of levator
• After 10msec relaxation of levator relaxation, a
train of high frequency synchronous activity
occurs in the pretarsal portion of orbicularis
• As the upper lid moves vertically down, the lower
lid moves medially in a horizontal
direction.However when the upper eyelid
touches the lower eyelid,the downward
movement of othe upper lid is also transmitted to
the lower lid and after contact the lower lid
moves

31. • During each blink, the upper eyelid covers
the center of pupil for a period of 0.10sec.
• Due to contraction of preseptal fibers, as
the upper eyelid reaches the limit of its
downward excrusion, electrical activity in
the orbicularis ceases and activity appears
in levator

32. Reflex Blinking
• Reflexly in response to a stimulus

33. Voluntary blinking and winking
• Is a willed coordinated closure and
opening movement of the eyelids in both
eyes
• The voluntary blink is under the control of
individual
• It is produced as a protective gesture

34. Winking
• Winking is unilateral voluntary lid closure
• It is part of facial expression
• Occasionally, a subject may learn to wink
with one eye but not with the other
• Both 'voluntary blinking and winking' are
produced by simultaneous contraction of
palpebral and orbital portions of orbicularis

35. BELL'S Phenomenon
• It is highly coordinated reflex in which
eyeball is rotated upward and outward on
closure of eyelids
• This is a protective mechanism
• On closure of eyelids,all electrical
activities in the levator cease and the
activity abruptly rises in the superior rectus
muscle and is inhibted in the inferior
rectus muscle

37. MCQS
1.Main Elevator of upper eyelid is
A)Frontalis
B)Muller's Muscle
C)Levator palpebrea superioris
D)None Of these

38. 2)Frontalis Muscle helps in
A)Elevating the Upper eyelid
B)Elevating Lower Eye lid
C)Retracting Lower Eyelid
D)Elevating eyeball

39. 3)Superior Muscle Helps in
A) Elevating Upper Eyelid
B)Elevating Lower Eye lid
C)Retracting Lower Eyelid
D)Elevating eyeball

40. 4)Levator muscles of two eyelid follow which
law
A) Sherrington's Law
B)Herring's Law
C)Law of gravity
D)All of these

41. 5)During closing movement which lid moves
12-20msec before the other one
A) Upper Eylid
B) Lower Eyelid
C)Both Moves simultaneously