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