Augenlids

Augenlids, or eyelids, are the paired movable folds that cover the front of the eye. Each lid protects the cornea, helps regulate the tear film, and contributes to eye lubrication and debris removal. Anatomically, the eyelid comprises skin externally, a thinned marginal zone containing eyelashes, a dense tarsal plate in the middle that gives structural stiffness, and a palpebral conjunctiva on the inner surface. The main muscles are the levator palpebrae superioris, which elevates the upper lid; the Müller (superior tarsal) muscle, which provides sympathetic-assisted retraction; and the orbicularis oculi, which closes the lids. The lid margin hosts the lash line, and the openings of the Meibomian glands; nearby are the sebaceous Zeis glands and the sweat Moll glands near the lash follicles.

Glandular elements contribute to the tear film: Meibomian glands secrete lipids that slow tear evaporation, while the lacrimal glands produce the aqueous component of tears. Blinking distributes the tear film across the ocular surface and aids debris removal. The lids also protect the eye from mechanical injury and help with eyelid lubrication throughout non-visual periods.

Common conditions affecting the eyelids include blepharitis (inflammation of the lid margin), ptosis (drooping of the upper lid due to lift muscle dysfunction), entropion (inward turning) and ectropion (outward turning) of the lid margin, chalazion (meibomian gland inflammation), and stye or hordeolum (infection near the lash follicle). Treatments range from lid hygiene and medical management to surgical procedures such as blepharoplasty, ptosis repair, or lash-margin adjustments, depending on the underlying cause.