ANATOMY OF THE EYELIDS

DR ARPITA

• Eyelids acts as shutters protecting the eye from injuries and excessive light

• Help in spreading tear film over cornea and conjunctiva via blinking and also helps eliminate tears from lacrimal lake

• Contribute to facial features of the individual • Relay information regarding the state of

wakefulness and attention of the person

EMBRYOLOGY• Development of the five pharyngeal arches occurs in

the first few weeks of gestation Mesenchymal proliferation occurs cephalad to the

first brachial arch to form the facial processes: the frontonasal, medial nasal, lateral nasal,maxillary and mandibular

• The upper eyelids are formed from the frontonasal process

• The lower eyelids are formed from the maxillary process

• The appearance of the eyelid fold marks the beginning of eyelid development during the sixth or seventh week of gestation. Incomplete eyelid fold development is thought to be the cause for a number of congenital eyelid anomalies, including ablepharon, cryptophthalmos, and microblepharon

• A. Eyelid fusion—8 to 10 weeks gestation.• colobomas of the eyelid margin B. Development of eyelid structures—3 to 4

months gestation. congenital ptosisC. Eyelid dysjunction—5 to 6 months gestation ankyloblepharon, blepharophimosis,

epicanthus, and euryblepharon.

GROSS ANATOMY

• 1)EXTENT AND POSITION OF EYELIDS –• Upper eyelid extends from eyebrow to

superior boundary of palpebral fissure• Lower eyelids – inferior boundary of

palpebral fissure to merge into cheeks• In primary postion upper lid covers one sixth

of cornea and lower lid just touches cornea

2)LID CREASES AND FOLDS

• Superior lid crease – attachment of LPS aponeurosis to skin

• Inferior lid crease – Fibrous slips from fascia surrounding inferior rectus muscle which attach to skin

• Lid folds – loose skin and subcutaneous tissue over the crease

• Lower lid has nasojugal and malar creases which are junction b/w skin of lids and denser tissue of cheek

• Limit spread of blood/fluid downwards from lids to cheek

• Superior lid crease is usually 8-12mm above the upper lid margin in Europeans .

• It is lower in Asians being around 2-5mm above upper lid margin – since the orbital septum and aponeurosis fuse at a lower level

• This allows preaponeurotic fat to occupy a postion more inferior and anterior creating the appearance of a fuller eyelid fold

3)CANTHITwo eyelids meet at the inner and outer canthiLateral canthus is in contact with eyeballMedial canthus is separated from globe by the tear lakeIn this area there is caruncle and plica semilunarisCARUNCLE- Modified skin containing sebaceous glands and

hairsPLICA SEMILUNARIS- Highly vascular crescent shaped fold of

conjunctiva .Vestigial structure analogous to nictitating membrane of animals

• 4) EYELID MARGINS – 2mm in width• Each lid margin divided into 2 parts by lacrimal

papilla – Lacrimal portion medially –devoid of lashes/glands and Ciliary portion laterally

• Approximately 100 to 150 cilia -upper eyelid, and 50 to 75 cilia -lower eyelid., arranged in two to three rows

Glands of Zeis and Moll open into each hair follicle

Dense plexus of nerves and vesssels around follicle – exquisite tactile sensibility

Both meibomian glands and eyelashes differentiate during the second month of gestation from a common pilosebaceous unit.

• Congenital distichiasis. • Acquired distichiasis

. The gray line is also referred to as the muscle of Riolan and represents the pretarsal orbicularis muscle on the eyelid margin.

An incision posterior to the gray line along the eyelid margin demarcates the anterior lamella from the posterior lamella of the eyelid

• 6)PALPEBRAL FISSURE• Space between upper and lower lid margins• At birth around 20 mm width and 8 mm

height• In adults around 30 mm width and 10 mm ht• In 50% people lateral canthus in about 2mm

higher than medial – greater than this produces a mongoloid slant

• Lateral canthus placed lower than medial –antimongoloid slant

STRUCTURE OF EYELID

SKIN

SUBCUTANEOUS TISSUE

STRIATED MUSCLES

SUBMUSCULAR CONNECTIVE TISSUE

FIBROUS LAYER

NON STRIATED MUSCLE

CONJUNCTIVA

SKINThinnest in the body contributing to ease of

mobility of lidsConstant movement with each blink – laxity

increases with age. This is called dermatochalasis

SUBCUTANEOUS TISSUE• Loose areolar connective tissue containing No

Fat – thus readily distended by oedema or blood

STRIATED MUSCLE• 1) Orbicularis oculi – Main protractor of

eyelid• Innervated by cranial nerve 7• Divided into three parts: • Pretarsal Involuntary eyelid movmts• Preseptal • Orbital Forced eyelid closure

• Pretarsal part- • Superficial origin-MCT• Deep origin – post lacrimal crest• Deep heads fuse near common

canaliculus to form Horners muscle (Pars lacrimalis)

• Contraction of which draws the eyelids medially and posteriorly. The resulting lateral pull creates a negative pressure in the lacrimal sac and draws the tears from the canaliculi into the sac.

• Laterally attaches at lateral canthal tendon

• Preseptal part arises from MCT medially and forms Lateral palpebral raphae laterally

• Orbital portion arises from MCT , frontal bone , maxillary bone – fibres form a ellipse and insert below origin

• Near eyelid margin fibres of pretarsal part – Muscle of Riolan (pars ciliaris) – creates gray line , plays a role in meibomian glandular discharge , blinking and position of eyelashes

• 2)LPS – Originates in the apex of orbit from sphenoid bone

• Courses forward as Muscular portion for around 40mm then descends vertically and fans out as an aponeurosis around 15mm long

• Whitnall ligament is located at transition zone – acts as a fulcrum for levator transferring its vector from ant-post to sup – inf direction

• Its analogue in lower lid is Lockwood ligament

• Whitnalls ligament is an important surgical landmark – easy to see intraoperatively as a strong white band of fibrous tissue

• Generally tissue superior to ligament is muscle while inferior is aponeurosis

• Lateral horn of levator aponeurosis divides lacrimal gland into orbital and palpebral lobes , attaches to LCT

• Medial horn attached to MCT and post lacrimal crest

• Lower down it divides into - anterior portion which inserts onto skin &

• Posterior portion - inserts onto lower half of tarsus

• Disinsertion , dehiscence of aponeurosis following trauma/Sx/senescence may give rise to PTOSIS

• Capsulopalpebral fascia in lower lid arises from inf rectus ms , encircles inf oblique ms .

• Its two heads join to form Lockwood ligament

• Fuses with orbital septum and inserts onto inf tarsal border

• Inf tarsal muscle analogous to Muller ms

SUBMUSCULAR CONNECTIVE TISSUE

• Nerves and vessels of lid lie in this layer , so to anaesthetise the lid injection is made in this plane

• Splits the lid into anterior and posterior lamella

• In upper lid communicates with subaponeurotic stratum of scalp – dangerous area of scalp

FIBROUS LAYER• 1)Tarsal plate - Dense fibrous tissue that forms the

skeleton of eyelids giving them shape and firmness• 30mm long , 1mm thick , upper tarsus 10mm in ht ,

lower tarsus 5mm in ht• Tarsal plates have rigid attachments to periosteum

via canthal tendons • The upper tarsus contains approximately 30

meibomian glands, and the lower tarsus contains approximately 20. The oil-secreting glands are aligned vertically

• 2) Septum orbitale – arises from periosteum over superior and inferior orbital rims

• Fuses with levator aponeurosis in upper eyelid and capsulopalpebral fascia in lower eyelid

• Separates the eyelids from the orbit and serves as an important anatomic barrier to infection, hemorrhage, and edema.

• Fat seen in an eyelid laceration means that septum has been cut and and that deeper tissues including eye and brain may be injured

• Orbital or preaponeurotic fat is an important surgical landmark as it lies right behind orbital septum and in front of levator aponeurosis

MEDIAL CANTHAL TENDON

• Can be divided into two parts – • Anterior part – arises from ant lacrimal crest• Angular artery and vein passes over medial

part of ligament , artery being medial to veins• Splits into upper and lower bands at medial

canthus , these contain lacrimal canaliculi ,enclose the caruncle , delimit and give shape to medial canthus

• Posterior part passes behind lacrimal sac from ant lacrimal crest to post lacrimal crest

• Fractures at medial canthus cause the medial canthus to be displaced laterally Telecanthus

• Medial canthal tendon is at about the same position as the Cribriform plate .In any operation involving the removing/repositioning of bone superior to MCT , there is risk of inadvertent CSF leak

LATERAL CANTHAL TENDON• Laterally attached to Whitnalls tubercle and

medially to ends of upper and lower tarsal plates

• Laxity of lower eyelid is major cause of ectropion – occurs due to lengthening of lateral canthal tendon with age

• Lateral canthotomy is a sight saving procedure to relieve orbital pressure due to retrobulbar hemorrhage

NON STRIATED MUSCLES• Mullers muscle originates on undersurface of

L.aponeurosis , inserts along upper eyelid superior tarsal margin

• Sympathetically innervated smooth muscle• Provides approx 2mm elevation to upper lid• If interrupted – eg HORNERS SYNDROME – mild ptosis

ensues• Peripheral arterial arcade is found b/w Lps aponeurosis

and Mullers ms - this vascular arcade serves as a surgical landmark to identify Mullers muscle

Muller's muscle: A 10-mm strip of Muller's muscle is preserved in this cadaver demonstrating its origin

from the underside of the reflected levator muscle

(thick arrow) and its insertion onto the superior

ridge of the tarsus.

CONJUNCTIVA• Posterior most layer

of eyelid• Consists of non

keratinising squamous epithelium

• Contains openings of glands of Krause and Wolfring

ARTERIAL SUPPLY• A network of vessels derived from two major

sources, the internal and the external carotid arteries, richly vascularizes the eyelids

• Collateralization between the internal and external systems contributes to the rapid wound healing and the low incidence of infection following eyelid surgery.

• As the vessels approach the eyelids, branches of the ophthalmic artery from the internal carotid artery and branches of the facial arteries off of the maxillary branch of the external carotid artery form the marginal and peripheral vascular arcades of the eyelids

•

VENOUS DRAINAGE

• Divided into pretarsal and postarsal• Pretarsal drains into angular vein medially

and superficial temporal vein laterally jugular veins

• Postarsal drainage is into orbital veins cavernous sinus

LYMPHATIC DRAINAGE

• Lymphatic vessels serving medial side of eyelid drain submandibular lymph nodes

• Those serving lateral portions of eyelids drain into preauricular deep cervical

NERVES

• Motor nerves – facial nerve (orbicularis)• oculomotor nerve (LPS)• Sensory nerves – derived from V1 and V2• Supraorbital , supratrochlear ,

infratrochlear ,lacrimal ,infraorbital ,infratrochlear

• Sympathetic nerves – Mullers muscle

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