THE EYELID

• Composition:
• Thin curtain of skin
• Muscle
• Fibrous Tissue
• Mucus Membrane
• That covers the eye like lens protectors on a camera.
• Number: 4
• Distribution: 2 for each each eye, i.e an upper and lower eyelid.

Functions

• Protects the eyeball from injury
• Interrupts and limits the amount of light entering the eye
• Distribution of tears over the surface of the cornea moist
• Provide nutrition achieved by blinking
• Assist in tear flow (their movement has a pumping action on the lacrimal sac.

Anatomical structure of the eyelid

Characteristics

• The eyelid is limited above by the eyebrow with when the lower eyelid merges with the check
• Each eyelid is divided by a horizontal furrow (sulcus) into
• An orbital and
• A tarsal portion.
• Palpebral fissure:
• An ecliptic opening formed by the eyelids (12 by 30mm)

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CHARACTERISTIC CONT’D

• Free margin of the eyelid are:
• Opening of the lacrimal canaliculus (puncta) located 5mm from the medial angle
• The eyelashes (cilia)
• Opening of the glands

Characteristics Cont’d

• Thickness – 2mm

Length – 30mm

• The medial 1/6 of the eyelid or the lacrimal portion has no cilia or glands opening
• The eyelid margins are rounded
• The lateral 5/6 has square edges

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Characteristics Cont’d

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• Grey line
• The intra marginal sulcus or grey line of the margin makes the anterior edge of the tarsal plate and divides it into:
• Anterior leaf (muscle and skin)
• Posterior leaf (tarsal and conjunctiva)

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Characteristics Cont’d

• Eyelashes originate anterior to the grey line and orifices of the tarsal glands are posterior to the grey line of the conjunctiva and stratified epithelium of the skin is at the level of the orifices of the tarsal gland
• Distribution of the eyelashes:
• Upper lid – more
• Lower lid – less

CHARACTERISTICS CONT’D

• Opening into the follicle of each cilium are:
• Ducts of sebaceous gland
• Large sweet glands of moll which open to these follicles and or directly onto the eyelid margin between the cilia

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Eyelid showing it’s internal structures

STRUCTURES

• The eyelid contain the following parts:
• Skin
• Muscle
• Orbicularis oculi muscle (CNVII)
• Orbital portion
• Palpebral portion
• Pre–septal portion
• Pre–tarsal portion

STRUCTURES Cont’d

• Eyelid refractors
• LPSM (CNIII)
• Superior tarsal muscles (sympathetic)
• IRM (CNVII)
• Inferior tarsal muscle (sympathetic)
• Fibrous tissue
• Septum orbital
• Tarsal plates conjunctiva

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Eyelid showing composition

NB: The orbital septum separates the intraocular contents from the eyelid while the inter – marginal sulcus provides a line of surgical dissection separating the anterior structures of the EL from the tarsal conjunctiva

The skin of the eyelid

• Thinnest of the body
• No fat in the subcutaneous
• Alveolar area
• Numerous folds
• Maybe distended by:
• Flood
• Fluid
• Underlying blood vessels may appear dark blue

ORBICULARIS OCULI MUSCLE (CNVII)

• They are striated skeletal muscles:
• Peripheral orbital portion (forcible closure of the eyelid)
• Central palpebral portion (involuntary blinking)
• Pre–septal portion overlying the orbital septum
• Pre–tarsal part underlying
• Upper tarsal plates
• Lower tarsal plate
• The arrangement at the medial canthus, support the lacrimal puncta and with each blink create suction in the lacrimal sac.

ORBICULARIS OCULI MUSCLE (CNVII) Cont’d

• The inferior tarsal muscle originate from the sheath of the IRM where it surrounds the IOM.
• It courses upward and inserts into:
• bulbar conjunctiva
• Expansion of the fascia of IRM that inserts into the tarsals
• The orbital septum separates the eyelid from the content of the orbit white.
• The capsule–palpebral fascia in the lower eyelid is equivalent to the levator aponeurosis

ORBICULARIS OCULI MUSCLE (CNVII) Cont’d

• The LPSM aponeurosis is located in the upper eyelid
• The LPSM (CNIII) is closely related to the SRM in it’s:
• Origin
• course
• The superior and inferior palpebral smooth muscles of Muller (sypmpathetic) are small sheet of muscles located immediately beneath the orbital portion of the palpebral conjunctiva.

ORBICULARIS OCULI MUSCLE (CNVII) Cont’d

• The superior palpebral muscle originate from the under surface of the LPSM
• The fibrous tissue of the eyelids consist of:
• Peripheral layer
• Palpebral fascia (septum)
• Orbital
• Thickened central portion

ORBICULARIS OCULI MUSCLE (CNVII) Cont’d

• The tarsal plates consist of:
• Firm connective tissue (not cartilage) that gives form and density to the free margin of the eyelids each.
• size: 1mm thick and 25–30 mm long
• Upper = 11mm
• Lower = 5mm wide
• Each tarsus contains:
• Sebaceous (Meibomian) gland margin
• Theses glands are arranged in a cycle round the tarsal plate and each consist of 10 – 15 acini placed irregularly around a central canal openings into the margin

ORBICULARIS OCULI MUSCLE (CNVII) Cont’d

• The sebaceous gland prevents:
• Overflowing of tears
• Makes possible an airtight closure of the eyelid
• Provides the superficial layer of the pre–corneal tear film
• Prevents the rapid evaporation of tears

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BLOOD SUPPLY TO THE EYELID

• This is derived from the marginal peripheral vascular arcades and formed by the lateral palpebral branches of:
• The lacrimal artery of
• Medial palpebral branches of the dorso nasal artery.
• Both are derived from internal carotid artery through the ophthalmic artery.

NERVE SUPPLY TO THE EYELID

• The ophthalmic (first) division of the trigeminal nerve (CNV) provides the sensory innervation of the:
• Upper eyelid
• Small lateral portion of the lower lid

LYMPHATIC SUPPLY

• The eyelids are drained by:
• A medial group which drains 2/3 of the lower eyelid and
• Medial 1/3 of the upper eyelid into the sub-maxillary lymph nodes

2. A lateral group drains the remaining portion of the eyelids to the pre–auricullar nodes