The Eyelids

OPTOMETRY · SEMESTER 2

Ocular Anatomy and Physiology

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The Eyelids

CHAPTER 3. THE EYELIDS

BY THE END OF THIS CHAPTER YOU WILL HAVE COVERED THE

FOLLOWING ASPECTS OF THE TOPIC:

EYELID -INTRODUCTION

ANATOMICAL SEGMENTS OF THE EYELID

INNERVATION AND VASCULARISATION OF THE EYELIDS

EYELID MOVEMENTS

SOME EYELID DISORDERS

SOME CONJUNCTIVAL DISORDERS

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1. INTRODUCTION
There is a superior ( upper) and an inferior (lower) lid to each eye.
The opened
angles or canthi.
The medial canthus, not so sharply angled like the lateral one but more
, lies 6mm from the eyebal
It is in which the caruncle and
The medial canthal ligament anchors the tarsal plates to the anterior and
posterior lacrimal crests via the anterior and posterior limbs respectively.
Levator palpebrae
superioris
Orbicularis
oculi muscle Fornix
Skin
Tarsus
Meibomian
gland
: Palpebral
Follicles 5 conjunctiva
of cilia
Cornea
= Palpebral conjunctiva
ols se Bulbar conjunctiva
Opening of meibomian gland Fornix
Fig. 3.1. Diagram of the upper eyelid in longitudinal section.
2. THE ANATOMICAL SEGMENTS OF THE EYELID.
2.1. The palpebral (lid) margin.
It is 2mm wide, has a rounded anterior border bearing the cilia ( eyelashes ),
and a sharp posterior border apposed to the globe.
re are aoe 1100 lashes in 2 or 3 rows in the upper eyelid and 50
An eyelash survives for about 5 months; its replacement is fully grown in 10
Posterior to the cilia on the free eyelid margin is a narrow grey line , marking
an avascular palpebral plane , the anterior boundary of the tarsal plate.
The grey line corresponds to the muscle {NNN ( section of the pretarsal
orbicularis) and it is not to be confused with the mucocutaneous junction.
Next to the openings is the mucocutaneous junction, representing the
anterior limit of the marginal strip of tear fluid.
The lacrimal puncti are located at the Fi@dialendslontheuppenandlowenlids.
Gray line
Meibomian gland
orifices
Mucocutaneous
junction
Conjunctiva Lash follicle
‘onjut a
Meibomian
gland
Orbicularis
oculi muscle
Fig.3.2. Diagrammatic representation of the palpebral margin.
2.2. The eyelid skin and subcutaneous tissue.
The eyelid skin is the thinnest in the body; it is devoid of subcutaneous fat ,
but alas has a loose connective tissue base , hence the propensity of the
eyelids to swell.
. In oriental people,
2.3. The orbicularis oculi muscle.
Is the muscle situated beneath the SKinNaNGIENISIFeSpOnSIDIEHOnEyenG
The fibres have a circular orientation , hence the sphincter like function of
the muscle.
Innervated by the facial nerve (cranial nerve Vil), it is divided into three
concentric zones: clogin “or and orbital. These divisions are both
The palpebral ( pretarsal and preseptal ) parts are more involved in
involuntary eye movements ( blink) , while the orbital portion is primarily
involved in forced eyelid closure ( winking and blepharospasm).
Part of the pretarsal orbicularis ( Horner's muscle ) , encircles both canaliculi
&nd facilitates tear drainage.
Around the eyelid margin , the pretarsal fibres form the muscle of Riolan.
————— eee
| ane
In the upper eyelid , the marginal arterial arcade lies 2mm superior to the
margin, near the follicles of the cilia, and anterior to the tarsal plate.
The peripheral arterial arcade lies
aponeurosis and Muller's muscle.
In the lower Pale there is often only SHelaberialarcadelocatedlanthe
Within the tarsal plates, lie the . They are
sebaceous gland
The canals of the glands almost completely traverse the tarsal plates and
open on the margin of the eyelid just in front of the mucocutaneous junction.
They sorte tpl Into the eee – this lipid helps stabilise the tear film and
2.5. The orbital septum ( palpebral fascia ).
It is a fibrous tissue
The orbital arp serves as a barrier between the orbit and the eyelid to
The orbital fat normally lies posterior to the orbital septum and anterior to

the levator aponeurosis . It is an important landmark during eyelid surgery,

Palpebral Ligaments

The palpebral or tarsal ligaments are bands of dense connective tissue
connecting the tarsal plates to the orbital rim and holding the tarsal plates in
position against the globe during eye and lid movements. The medial
palpebral ligament runs from the medial edge of each tarsal plate to the
medial orbital rim, where it divides into two limbs. One limb attaches to the
posteriorlacrimal crest and the other to the anterior lacrimal crest. Both

limbs lie anterior to the orbital septum

Tarsal Plate

Each eyelid contains a tarsal plate (tarsus) that gives the lid rigidity and
structure and shapes it to the curvature of the globe. The tarsal plate in the
upper lid is approximately 11 mm high, and the inferior tarsal plate is
approximately 5 mm high
2.6. The eyelid retractors.
In the lower lid, the retractors are the ial ei orn
a. The levator palpebrae superioris, a striated muscle innervated by the
oculomotor nerve (cranial nerve II! ), is responsible primarily for eyelid
opening.
It originates on the lesser wing of the sphenoid bone above and in front of
the optic foramen, and its sheath blends with the sheath of the superior
rectus muscle. As the levator approaches the eyelid from its posterior origin
at the orbital apex, a ligament, the superior transverse ligament (Whitnall’s
ligament) may act as a fulcrum, changing the anteroposterior direction of
the levator to Superoinferior Originates in the apex of the orbit, just above
the annulus of Zinn, passes forward beneath the orbital roof towards the
It becomes ELE in the lid, where the aponeurosis fans out on either
It inserts into the skin ( causing the eyelid crease ) and the anterior surface
of the tarsal plate.
The muscular portion of the levator is approximately 40mm long , while the
aponeurosis is
b. Muller’s muscle originates at
This srmpathreticaly innervated muscle, provides approximately 2mm of
The is located between
c. The capsulopalpebral fascia in the lower eyelid is analogous to the levator
aponeurosis in the upper eyelid.
d. The inferior tarsal muscle in the lower eyelid is analogous to Muller’s
19
Glands of the Lids
The meibomian glands (tarsal glands) are sebaceous glands embedded in
the tarsal plate. Meibomian glands are ho/ocrine glands; their secretion is
produced by the decomposition of the entire cell Each consists of 10 to 15
lobes or acini attached to a large central duct. These long, multilobed glands
resemble a large bunch of grapes and are arranged vertically. Approximately
30 to 40 meibomian glands are found in the upper lid and 20 to 30 in the
lower lid.14 On eyelid eversion the vertical rows of the meibomian glands
can sometimes be seen as yellow streaks through the palpebral conjunctiva.
These glands secrete the outer lipid layer of the tear film.
The sebaceous glands of Zeis secrete sebum into the hair follicle of the cilia,
coating the eyelash shaft to keep it from becoming brittle and dry. They are
histologically the same to the meibomian gland however they consist of only
1 to 2 acini
The glands of Moll are modified sweat glands located near the lid margin.
The Moll gland is an apocrine gland; its secretion is composed not of the
whole cell but of parts of the cellular cytoplasm. Their ducts empty into the
hair follicle, into the Zeis gland duct, or directly onto the lid margin. Similar
glands found in the axillae are scent organs, but the purpose of the Moll
glands in the eyelid is unclear. Histochemical studies have identified
markers for substances in Moll glands that suggest a role in immune defense
Accessory lacrimal glands are groups of secretory cells with a truncated-
pyramid shape arranged in an oval pattern around a central lumen. The
accessory lacrimal glands are densely innervated, as is the main lacrimal

gland.

Palpebral Conjunctiva

The palpebral conjunctiva is composed of two layers, a stratified epithelial
layer and a connective tissue stromal layer, the submucosa
Goblet cells, which produce the innermost mucous layer of the tear film, are
scattered throughout the stratified columnar conjunctival epithelium. These
cells are most numerous in the inferior nasal aspect of the tarsal
conjunctiva.38 Their number decreases with advancing age and increases in
inflammatory conditions. A goblet cell produces mucin droplets that
accumulate, causing the cell to swell and become goblet shaped. The surface
of the cell finally ruptures, releasing mucus. Parasympathetic and
sympathetic nerves have been associated with goblet cells and may play a
role in their secretion.39 Invaginations of conjunctival epithelium, often
located near the fornix, are called crypts of Henle. Goblet cells release their
mucus into the cavity formed
by these invaginations, and the mucus may become trapped if the opening

to the crypt is narrow

INNERVATION OF EYELIDS

The ophthalmic and maxillary divisions of the trigeminal nerve provide
sensory innervation of the eyelids. The upper lid is supplied by the
SUpraorbital)'supratrochlear)infratrochlear) and lacrimal nerves, branches of
the ophthalmic division. The supply to the lower lid is by the infratrochlear
branch of the ophthalmic nerve and the infraorbital nerve, a branch of the

maxillary division

BLOOD SUPPLY OF EYELIDS

The blood vessels are located in a series of arcades or arches in each eyelid.
The vessels forming these arcades are branches from the medial and lateral
palpebral arteries. The medial and lateral palpebral arteries are branches of
the ophthalmic and lacrimal arteries, respectively.
2.7. The conjunctiva.
The conjunctiva is a thin, translucent mucous membrane that runs from the
limbus over the anterior sclera, forms a cul-de-sac at the superior and
inferior fornices,
and turns anteriorly to line the eyelids. It ensures smooth movement of the
eyelids over the globe. The conjunctiva can be divided into three sections
that are continuous with one another: (1) the tissue lining the eyelids is the
palpebral conjunctiva, or tarsal conjunctiva; (2) the bulbar conjunctiva
covers the sclera; and (3) the conjunctival fornix is the cul-de-sac connecting
palpebral and bulbar sections
The /imbusis the location of stem cells for bulbar conjunctiva and the
mucocutaneous junction is the site of stem cells for palpebral conjunctiva
.The eyelids are lined by mucous membrane, the palpebral conjunctiva ,
which is in continuity with the bulbar conjunctiva via the fornices.
The palpebral conjunctiva is
. At the limbus, the attachment

to underlying tissues is tight again

HISTOLOGIC FEATURES

The conjunctiva is composed of two layers, a stratified epithelial layer and a
connective tissue stromal layer, the submucosa.
As amucous membrane, the conjunctiva has an epithelium and substantia
propria.
The conjunctival epithelium
enh. continuous withthe corneal gptheum at heb a with
the skin at the eyelid margin.
It contains numerous goblet cls these cals secrete mci int the ear
The substantia propria (conjunctival submucosa), has two layers: a
anes lacrimal oeibe are found in the substantia propria. Wolfring
There are two specialisations of the conjunctiva in the medial fornix:
a. Plica semilunaris (the semilunar fold ), a loose fold which facilitates lateral
It is rich in goblet cells and it is highly
vascularised.
The floor of the lacrimal lake is the plica semilunaris. This narrow, crescent-
shaped fold of conjunctiva, located in the medial canthus, allows for lateral
movement of the
eye without stretching the bulbar conjunctiva.
b.The caruncle, a nodule of modified skin containing accessory lacrimal
glands and sebaceous glands, is the second specialized structure . It is
covered with epithelium
that contains goblet cells and fine hairs and their associated sweat and
sebaceous glands. The sebaceous glands are a likely source for the
occasional accumulation of matter in the medial canthus of the healthy eye.

Its function is poorly understood.

TENON’S CAPSULE

Below the conjunctival stroma is a thin, fibrous sheet called Tenon’s capsule
(fascia bulbi). Tenon’s capsule serves as a fascial cavity within which the
globe can move. It protects and supports the globe and attaches it to the
orbital connective tissue

CONJUNCTIVAL LYMPHATICS

The conjunctival lymphatic vessels are arranged in superficial and deep
networks within the submucosa.those from the lateral aspect empty into the
parotid lymph node, and those from the medial aspect empty into the

submandibular lymph node

CONJUNCTIVAL INNERVATION

Sensory innervation of the bulbar conjunctiva is through the long ciliary
nerves. Sensory innervation of the superior palpebral conjunctiva is provided
by the frontal and lacrimal branches of the ophthalmic nerve. Innervation of
the inferior palpebral conjunctiva is provided by the lacrimal nerve and the
infraorbital branch of the maxillary nerve. All sensory information is carried
in the trigeminal nerve.
3. INNERVATION AND _VASCULARISATION OF THE EYELIDS.
Two divisions of the trigeminal nerve supply sensation to the eyelids, the
ophthalmic and the maxillary divisions.
Other branches of the ophthalmic division ,
The ophthalmic artery supplies blood to the lids via
palpebral aes Each palpebral artery gives rise to
In the upper lid there is a marginal (2mm above the eyelid margin ) arcade
and a peripheral ( above the tarsal plate and anterior to Muller’s muscle )
arterial arcade.
In the lower lid, there is usually only one arcade, 4mm below the margin.
Numerous anastomoses between adjacent arteries connect the internal and
external carotid systems.
The main venous drainage of the lids is to the angular and ophthalmic veins
medially and the superficial temporal vein laterally.
vos the medial canthus and lower lid drain into ay
4. EYELID MOVEMENTS.
Eyelid movements are important for the protection of the eyeball and for
the elimination of the tears. they also contribute to facial expression.
4.1. Eyelid closure , takes several forms, effected by functionally different
groups of the orbicularis oculi muscle.
Reflex ond is a protective mechanism initiated by tactile, visual, or
Spontaneous blinking , by contrast , occurs regularly without obvious stimuli
, after the first few months of life.
A wink is a voluntary unilateral closure which interrupts vision.
Contraction of the palpebral portion closes the eyelid gently, and the
palpebral orbicularis is the muscle of action in an involuntary blink and a
voluntary wink; relaxation of the levator muscle follows.
Forced eyelid closure or blepharospasm is often voluntary but may be
involuntary.
Automatic eyelid closure during slee
This protective up turning
4.2. Eyelid opening is due to the actions of : !evator palpabrae and Muller's
muscle.
21
The levator muscle is innervated by the oculomotor nerve and Muller’s by
sympathetic fibres.
When the orbital portion of the orbicularis contracts, the eye is closed
tightly.
Spontaneous involuntary blinking renews the precorneal tear film. A reflex
blink is protective and may be elicited by a number of stimuli— a loud noise;
corneal, conjunctival, or cilial touch; or the sudden approach of an object
5. SOME EYELID DISORDERS.
The inability to close the eyelidsis called lajophthalmos. It is due to a
dysfunction of the orbicularis oculi muscle.
Ectropion is the outward turning of the eyelid margin.
Entropion is the inward turning of the lid margins.
Entropion causes trichiasis , a condition whereby the eyelashes are turned in
and rub against the eyeglobe.
Trichiasis and entropion, are characteristic of trachoma, an infectious eye
disease encountered in the developing world.
Stye or external hordeolum is a localised abcess of an eyelash follicle.
Internal hordeolum is an abcess of the meibomian gland;if this abcess
becomes granulomatous,it is called a chalazion.
Blepharitis is chronic infection of the eyelid margins.
6. SOME CONJUNCTIVAL DISORDERS.
Conjunctivitis means inflammation of the conjunctiva. May be caused by
infections, allergies or chemical irritation.
Ophthalmia neonatorum is conjunctivitis occurring in the newborn.
Pingueculum is a small whitish degenerative mass , usually next to the
limbus.
Pterygium is an abnormal, wedge-shaped conjunctival tissue growing over
the cornea.
Naevus is a brown ( pigmented) benign lesion, usually on the bulbar
conjunctiva.
Various types of tumours can develop on the conjunctiva; squamous cell
carcinoma is the most frequently encountered malignant tumour of the
conjunctiva.