Anatomy
Eyelid Anatomy: Structure, Function, and Common Conditions
The eyelids are complex, multi-layered structures that protect the eye, spread the tear film with each blink, and regulate light entry. They contain sebaceous meibomian glands, sweat glands, hair follicles (eyelashes), and the orbicularis oculi muscle that controls blinking.
Anatomy Overview
Eyelid Anatomy: Structure, Function, and Common Conditions
Structure & Components
Drooping upper eyelid (ptosis) blocking vision — functional concern
Entropion: eyelid turns inward, causing lashes to scratch cornea
Ectropion: eyelid turns outward, causing poor tear drainage and exposure
Blepharitis: crusty, red, itchy eyelid margins
Stye (hordeolum): painful red lump on eyelid from infected gland
Chalazion: painless lipogranuloma from blocked meibomian gland
Functions & Physiology
Orbicularis oculi muscle encircles the eye controlling blinking and squinting
Levator palpebrae superioris muscle lifts the upper eyelid
20-30 meibomian glands per eyelid secrete the oil layer of the tear film
Eyelashes trap debris and sweat, acting as a sensory trip wire
Skin of eyelid is thinnest in the body — only 0.5mm thick
Each blink takes only 150-400 milliseconds — we blink 15-20 times/minute
Key Points
Ptosis: surgical levator resection or frontalis sling procedure
Entropion: lid sutures (temporary) or full surgical repair
Ectropion: horizontal lid-shortening procedure
Blepharitis: warm compresses and lid hygiene
Stye: warm compresses; incision and drainage if not resolving
Chalazion: steroid injection or surgical curettage
Blepharoplasty for excess skin and cosmetic correction
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