Other - Eyelids

Question 1

What is the function of the eyelids?

Answer 1

1) Protection - against excessive light or injury
2) Lubrication - by spreading the lacrimal fluid across the eye

Question 2

Layers of the eyelid

Answer 2

Consists of 5 layers, superficial to deep:

1) Skin and subcutaneous tissue
2) Orbicularis oculi
3) Tarsal plates
4) Levator apparatus
5) Conjunctiva

Question 3

Skin and subcutaneous tissue of the eyelid

Unique features?

Answer 3

Very thin skin

Only loose connective tissue makes the subcutaneous tissue - no fat.

As a result the eyelid is readily distended by oedema or blood.

Eyelashes are attached here with their accompanying modified sweat glands, called the ciliary glands of Moll. There are also sebaceous glands called the glands of zeis.

Question 4

Orbicularis oculi

Attachments?

Action?

Innervation?

Answer 4

Origin - medial orbital margin, the medial palpebral ligament and lacrimal bone.

Insertion - Into the skin around the margin of the orbit, and the superior and inferior tarsal plates.

Action:

• Palpebral part - gently closes the eyelids
• Lacrimal part - involved in the drainage of tears
• Orbital part - tightly closes the eyelids

Innervation - Facial nerve (temporal and zygomatic branches)

Question 5

Tarsal plates

Purpose?

Clinical relevance

Answer 5

There are two plates per eye - superior tarsus (upper eyelid) and inferior tarsus (lower eyelid).

It has two functions:
1) Provides attachment for the levator palpabrae superioris.

2) Contains tarsal glands - prevents eyelids from sticking together and secretes an oily substance onto the eye to prevent evaporation of the eye’s tear film.

Clinical relevance

Styes - infection of the hair follicle (external) or tarsal glands (internal).

Chalazion - painless granuloma of the tarsal glands, whereas styes are normal painful.

Question 6

Levator apparatus

Components?

Attachments

Action

Innervation

Answer 6

Levator palpabrae superioris and superior tarsal muscle both act to open eyelids. Only present on the upper eyelid.

Levator palpabrae superioris (LPS)

Origin - lesser wing of sphenoid,

Inserts - upper eyelid and the superior tarsal plate

Action - opens the eyelid

Innervation - superior branch of the oculomotor nerve (CN III)

Superior tarsal muscle

Origin - underside of the LPS

Inserts - superior tarsal plate

Action - assist LPS in opening the eyelid.

Innervation - sympathetic fibres from the superior cervical ganglion

Question 7

Conjunctiva

What is it?

Clinical relevance?

Answer 7

Palpebral conjunctiva is the deepest layer of the eyelid.

It is a thin mucous layer that is reflected onto the sclera (bulbar conjunctiva).

Clinical relevance - conjunctivitis (pink eye) - bacteria or viral particles accumulate under the eyelid.

Question 8

Vasculature of the eyelids

Answer 8

Arterial supply:

1) Ophthalmic artery - many branches (lacrimal, medial palpebral, supraorbital, dorsal nasal and supratrochlear arteries).
2) Facial artery - angular branch
3) Superficial temporal artery - transverse facial artery branch

Venous drainage:

1) Medial palpebral vein
2) Superficial temporal vein

Question 9

Innervation of the eyelids

Answer 9

Sensory innervation:

Branches of the trigeminal nerve:

1) Ophthalmic nerve (V1) - upper eyelid

Supraorbital, supratrochlea, infratrochlear and lacrimal branches.

2) Maxillary nerve (V2) - lower eyelid

Infraorbital and zygomaticofacial branches.