Free previewYou're reading the free part of this topic. The rest is included with Clinical.See what's included
Eyelid anatomy
Anatomy & Optics
Key Points
- •The eyelid has 7 layers (anterior to posterior): skin (thinnest in body), orbicularis oculi (CN VII), orbital septum, pre-aponeurotic fat, levator aponeurosis (CN III) + Muller's muscle (sympathetic), tarsal plate (with meibomian glands), palpebral conjunctiva
- •The grey line is the mucocutaneous junction dividing the anterior lamella (skin + orbicularis) from the posterior lamella (tarsus + conjunctiva) - critical surgical landmark for lid margin laceration repair; anterior: lash follicles, Zeis, Moll; posterior: meibomian gland orifices
- •Levator function assessment: normal ≥15 mm; poor <5 mm (requires frontalis sling); Muller's muscle contributes ~2 mm (sympathetic - Horner ptosis responds to phenylephrine 2.5%); Whitnall's ligament is the transition point from levator muscle to aponeurosis
- •Orbital septum separates preseptal from postseptal space - barrier to infection spread: preseptal cellulitis (benign) vs orbital cellulitis (emergency: proptosis, EOM restriction, optic nerve risk)
- •Meibomian glands (~25 upper, ~20 lower): holocrine sebaceous glands producing the lipid layer of the tear film; dysfunction (MGD) → most common cause of dry eye; blocked → chalazion; sebaceous carcinoma may masquerade as chronic chalazion
Free preview ends here
Keep reading Eyelid anatomy
13 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Clinical features