Eyelids Flashcards
What are the eyelids?
thin curtains of skin, muscle, fibrous tissue and mucous membrane
What are the 2 key functions of the eyelids?
- protect eyes from injury and excessive light
- distribute tears over ocular surface during blinking
What is the position of the upper eyelid when open?
normally just overlaps the corneoscleral junction
Which eyelids undergoes the most displacement during eyelid closure?
upper lid (lower lid moves only minimally during normal blinking)
On external examination, which 2 portions can each lid be divided into?
- orbital portion
- tarsal portion
What divides each lid into orbital and tarsal portinos?
horizontal palpebral sulcus (most evident on uppder lid)
Where is the horizontal palpebral sulcus most evident?
upper lid (superior palepbral sulcus)
What limits the upper and lower lids?
upper lid limited superiorly by eyebrow, lower lid blends with skin of cheek
What are the names of the points at which upper and lower lids meet?
medial and lateral canthi or angles
What separates the medial and lateral canthi from each other?
palpebral fissure (elliptical opening)
What is the positioning of the lateral canthus?
acute angle (60 degrees) and lies close to the eyeball
What is the shape and positioning of the medial canthus?
rounded, elongated medially, lies 6mm from the eyeball
What separates the medial canthus from the eye?
lacus lacrimalis (lake of tears)
What is located within the lacus lacrimalis?
small raised red swelling, the curuncula lacrimalis
What is the most conspicious racial difference in the shape and form of the eyelids and canthi?
vertical epicanthal fold in oriental and asian races
How long are the eyelid margins?
30mm
How thick are the eyelid margins?
2mm
What shape are the eyelid margins for their length?
relatively square in profile along most of their length, except medial one-sixth, which is rounded and lacks eyelashes
What are eyelashes?
modified, thick, stiff hairs that occur as double or triple rows close to the anterior lid margin
What is the arrangement of eyelashes?
double or triple rows, close to anterior lid margin
curl away from lashes of opposite lid
What are 4 notable features on the lid margins?
- lacrimal puncta
- tarsal (meibomian) glands
- skin/conjunctival transition zone
- grey line
Where are lacrimal puncta located?
at the medial ends of the upper and lower lids
What is the function of the lacrimal puncta?
drain tears from the lacus lacrimalis
How can the lacrimal puncta be more easily identified?
if tension is places on the lids, causing the papillae to blanch
What are the tarsal (meibomian) glands?
visible to the naked eye as a row of minute openings on the lid margin posterior to the eyelash follicles
How many tarsal (meibomian) glands are there on the eyelids?
around 30 in the upper lid, slightly fewer in the lower lid
What and where is the skin/conjunctival transition zone?
mucocutaneous junction, occurs at level of opening of the tarsal glands
What is the grey line?
marks anterior boundary of the tarsal plate (useful landmark for surgical incisions)
What type of secretion do sweat glands on the eyelid employ?
eccrine secretion
What is the function of the loose areolar layer of the eyelid?
fluids can track down into the eyelids from subaponeurotic layer of scalp
nerve and vessels of eyelid mostly found in this layer
What are ciliary glands (of Moll)?
modified sweat glands, unbranched tubular type, apocrine secretion
In which layer of the eyelid are nerves and vessels mostly found?
loose areolar layer
Between which layers is the loose areolar layer of the eyelid found?
between the tarsal plate and orbicularis oculi
What are the sebaceous glands (of Zeis)?
associated with eyelashes, sebaceous glands in follicle of holocrine type
What is another name for the glands of Moll?
ciliary glands
What type of secretion is performed by ciliary glands (of Moll)?
apocrine secretion
What is another name for glands of Zeis?
sebaceous glands
What type of secretion is performed by sebaceous glands of Zeis?
holocrine
Are there arrector pili muscles associated with eyelashes?
no
What are 2 accessory lacrimal gland types?
glands of Krause and Wolfring
What type of tissue forms the tarsal plate?
dense fibrous connective tissue
What are tarsal glands?
modified sebaceous glands, holocrine-type secretion
What type of secretion is performed by meibomian (tarsal) glands?
holocrine
What lines the ducts of tarsal glands?
stratified epithelium
What is the function of the subtarsal sulcus?
traps particles in tear film/conjunctival sac
What structure forms the fibrous framework of the eyelids?
orbital septum arising from the orbital margin and the tarsal plates
What are the tarsal plates?
modified regional thickenings of the orbital septum that provide rigidity to the upper and lower lids and separate the orbit and its contents from the lids
What ageing changes can affect the orbital septum?
herniation of orbital fat through weakened regions of septum produces bulging, sagging lids (blepharochalasis)
What is the width of the tarsal paltes from medial to lateral borders?
25-30mm
How thick are the tarsal plates?
1mm thick
What are the heights of the upper and lower tarsal plates?
upper plate 10-12mm, lower plate 5mm
What are the attachments of the tarsal plates at either end?
continuations, the medial and lateral palpebral ligaments
What are the attachments to the anterior and posterior surfaces of the tarsal paltes?
skin moves freely over anterior surface
conjunctiva tightly bound to posterior surface
What can be seen on external examination fo an everted eyelid?
vertical rows of yellowish tarsal glands
What type of glands are tarsal glands?
modified sebaceous glands
Wher are tarsal glands situated?
embedded in the matrix of the tarsal plate
What is the histology of the tarsal glands?
acinar cells are replete with lipid droplets that are secreted in a holocrine manner on to the eyelid margin, which retains tears in the conjunctival sac and contributes to the lipid layer of the precorneal tear film
How do the tarsal glnds secrete droplets?
lipid droplets secreted in holocrine manner onto the eyelid margin
Which 2 places do lymphatics from the eyelids drain to?
- superficial parotid lymph nodes
- submandibular lymph nodes
Where does the pretarsal portion of the eyelid derive its aterial supply?
superficial temporal and facial arteries (branches of external carotid)
What is the arterial blood supply to the post-tarsal portion of the eyelid?
branches of the ophthalmic artery (branch of internal carotid artery)
What is the venous drainage of the eyelid?
follows similar pattern to arterial supply
consideration of anastomoses between the internal and external carotid arteries
post-tarsal venous drainage is via ophthalmic veins to cavernous sinus
What are 8 arteries that supply the eyelids and identify them on the image
- Lacrimal artery
- branch of superficial temporal artery
- Lateral palpebral arteries (branches of lacrimal artery)
- Transverse facial artery
- Infraorbital artery
- Supraorbital artery
- Supratrochlear artery
- Medial palpebral arteries (branches of ophthalmic artery) –> form marginal and peripheral arterial arches
What are 6 enrves which supply the eyelids and identify them on the diagram
- Lateral palpebral branch of lacrimal nerve (V1)
- Zygomatico-facial nerve (V2)
- Supraorbital nerve (V1)
- Supratrochlear nerve (V1)
- Infratrochlear nerve (V1)
- Infraorbital nerve (V2)
What is a chalazion?
localised, painless swelling in the lid caused by obstruction and chronic inflammation of a tarsal gland
What is another term for a hordeolum?
sty
What is a hordeolum?
acute infection of an eyelash follicle or its sebaceous gland, infection fo a ciliary sweat gland (exernal hordeolum) or acute infection of a tarsal gland (internal hordeolum)
What is an external hordeolum?
acute infection of eyelash follicle or its sebaceous gland / infection of ciliary sweat gland
What is an internal hordeolum?
acute infection of a tarsal gland
What is an ectropion?
drooping of the lower lid owing to paralysis of orbicularis oculi
Why can ectropion cause epiphora (excessive tearing)?
paralysis of fibres of orbicularis that enloses the lacrimal sac means the puncta no longer suck up tears, which may pass over the lid margin
What causes eyelids to close?
action of the palpebral fibres of the orbicularis oculi, and relaxation of levator palpebrae superioris
What causes the eyelids to open?
pull of levator palpebrae superioris on the skin, tarsal plate and forniceal conjunctiva
What are the 3 innervation sources to the muscles that move the eyelids?
- Facial nerve - orbicularis oculi (007)
- Oculomotor nerve - levator palpebrae superioris
- Sympathetic nerves - smooth muscle component, superior tarsal (Müller’s) muscle
When is the sympathetic supply to the superior tarsal (Müller’s) muscle important?
times of fear or excitement, when the width of the palpebral fissure is further increased
What is a common clinical condition causing drooping of the eyelid (ptosis)?
Horner syndrome
What are the 4 classic symptoms of Horner syndrome?
- unilateral ptosis
- unilateral miosis
- unilateral dry facial skin (anhidrosis)
- blushing on affected side
What are 4 examples of lesions that can cause Horner syndrome?
- iatrogenic interruption of the sympathetic chain in the neck
- dissection of the internal carotid artery
- cervical disc dislocation
- lysis of the first rib affecting the stellate ganglion associated with Pancoast tumour
In addition to the classic 4, what are 2 further possible symptoms of Horner syndrome?
(4 = ptosis, miosis, anhidrosis, blushing)
- heterochromia
- enophthalmos
