Orbit Volume 3 Flashcards
What is the anatomical significance of the eyelid crease?
Denotes the site of levator aponeurosis attachment to the pretarsal obicularis oculi and skin
How does the eyelid crease typically differ in Asian patients?
Eyelid crease is typically lower in Asian patients
What muscle is the primary protractor of the eyelid?
Orbicularis oculi
Name the 3 parts of the orbicularis oculi muscle.
- Pretarsal 2.Preseptal 3.Orbital
What portions of the orbicularis oculi are integral to involuntary closure of the eyelid (e.g. blink)?
Preseptal and pretarsal
What muscle makes up the lateral canthal tendon?
Pretarsal orbicularis oculi
What muscle makes up the gray line of the eyelid?
Muscle of Riolan (lies posterior to orbicularis oculi)
Where does the orbital septum fuse with the levator aponeurosis in the upper eyelid?
2 to 5 mm above the superior tarsal border
What important landmark in eyelid surgery and laceration repair in determining location of orbital septum and levator aponeurosis?
Central orbital fat pad
What are the retractors of the upper eyelid?
Levator muscle (aponeurosis) and Muller’s muscle
What are the retractors of the lower eyelid?
Capsulopalebral fascia and inferior tarsal muscle
What is the average length of the muscular portion of the levator muscle?
40 mm
What is the average length of the levator aponeurosis?
14 to 20 mm
What structure divides the lacrimal gland into the orbital and palpebral lobes?
Lateral horn of the levator aponeurosis
Where does the posterior levator aponeurosis attach to the anterior surface of the tarsus?
Approx.3 mm above the eyelid margin
What is the average height of the upper eyelid tarsus?
10 to 12 mm
What is the average height of the lower eyelid tarsus?
4 mm
What is the average thickness of the tarsus?
1 mm
What nerve innervates the levator muscle?
Superior division of CN Ill (also supplies superior rectus muscle)
What substance do Goblet cells produce?
Mucin (makes up posterior layer of the tear film)
Where are the meibomian gland orifices of the eyelid located?
Just posterior to the gray line
What is the approximate number of eyelashes in the upper eyelid?
100
What is the approximate number of eyelashes in the lower eyelid?
50
What is the approximate number of the meibomian glands in the upper eyelid?
25
What is the approximate number of meibomian glands in the lower eyelid?
20
What is the venous drainage of the pretarsal eyelid?
Angular vein medially and superficial temporal vein laterally
What is the venous drainage of the posttarsal eyelid?
Orbital veins and facial vein (along with pterygoid plexus)
What glands are located within the tarsus?
The meibomian glands
What is the function of the meibomian glands?
Holocrine, oil-producing sebaceous glands
