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Anterior segment of eyeball

From Wikipedia, the free encyclopedia

Front third of the eye

Anterior segment of eyeball
Human eye Anterior Segment - Magnified view seen on examination with a slit lamp under diffuse illumination showing conjunctiva overlying the white sclera, transparent cornea, pharmacologically dilated pupil and cataract
Details
Identifiers
Latin	segmentum anterius bulbi oculi
MeSH	D000869
Anatomical terminology [edit on Wikidata]

Theanterior segment oranterior cavity^[1] is the front third of theeye that includes the structures in front of thevitreous humour: thecornea,iris,ciliary body, andlens.^[2]^[3]^[4]

Within the anterior segment are two fluid-filled spaces:

theanterior chamber between the posterior surface of the cornea (i.e. thecorneal endothelium) and the iris.
theposterior chamber between the iris and the front face of the vitreous.^[2]

Aqueous humour fills these spaces within the anterior segment and provides nutrients to the surrounding structures.

Some ophthalmologists and optometrists specialize in the treatment and management of anterior segment disorders and diseases.^[3]

^"Medical gallery of Blausen Medical 2014".WikiJournal of Medicine.1 (2). 29 August 2014.doi:10.15347/WJM/2014.010.
^^a ^bCassin, B. and Solomon, S.Dictionary of Eye Terminology. Gainesville, Florida: Triad Publishing Company, 1990.
^^a ^b"Departments. Anterior segment."Archived September 27, 2006, at theWayback MachineCantabrian Institute of Ophthalmology.
^Fraser, AS; Ang, M; Bellchambers, A; Chu, CJ; Denniston, AK; Downie, LE; Evans, T; Hau, S; Huang, AS; Keane, PA; Liu, X; Mehta, JS; Ometto, G; Petzold, A; Tsui, E; Fraser, TS; Xu, B; Thaung, C; Solebo, AL (14 August 2025)."Proposed Nomenclature for Landmarks in Anterior-Segment OCT: The APOSTEL-AS Panel Consensus".JAMA Ophthalmology.143 (9):749–757.doi:10.1001/jamaophthalmol.2025.2414.PMC 12355391.PMID 40810988.

Anterior+Eye+Segment at the U.S. National Library of MedicineMedical Subject Headings (MeSH)

Anatomy of theglobe of thehuman eye

Sclera	Episcleral layer Schlemm's canal Trabecular meshwork
Cornea	Limbus layers Epithelium Bowman's Stroma Dua's layer Descemet's Endothelium

Choroid	Capillary lamina of choroid Bruch's membrane Sattler's layer
Ciliary body	Ciliary processes Ciliary muscle Pars plicata Pars plana
Iris	Stroma Pupil Iris dilator muscle Iris sphincter muscle

Retina (inner)

Layers	Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium
Cells	Photoreceptor cells (Cone cell,Rod cell) → (Horizontal cell) →Bipolar cell → (Amacrine cell) →Retina ganglion cell (Midget cell,Parasol cell,Bistratified cell,Giant retina ganglion cells,Photosensitive ganglion cell) →Diencephalon:P cell,M cell,K cell,Muller glia
Other	Macula Perifoveal area Parafoveal area Fovea Foveal avascular zone Foveola Optic disc Optic cup Ora serrata

Anatomical regions
of the eye

Anterior segment	Adnexa (Eyebrow,Eyelid,Conjunctiva,Lacrimal system,Orbit) Fibrous tunic Anterior chamber Aqueous humour Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn
Posterior segment	Vitreous chamber Vitreous body Retina Choroid