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Basic Eye Anatomy

Jonathan A. Barnett

  • Sclera - White wall of the eye

  • Conjunctiva - Translucent, vascularized tissue that covers the anterior sclera (bulbar conjunctiva) and lines the inner aspect of the eyelids (palpebral conjunctiva). When the eyes get “red,” it is usually the conjunctiva, and not the sclera, that is irritated (conjunctival vessels dilate).

  • Cornea - Transparent, bubble-like structure in front of the eye.

  • Iris - “colored” part of the eye that dilates and constricts the pupil to let in more or less light

  • Pupil - the central hole in the iris

  • Anterior Chamber (AC) - the space between the cornea and the iris

  • Aqueous Humor - clear fluid that fills the anterior and posterior chambers, produced by the ciliary body. Nourishes the cornea. The balance of aqueous production and drainage dictates the intraocular pressure (IOP).

  • Iridocorneal angle (or just, the Angle) - angle between the iris and the cornea and site of the Trabecular Meshwork, which drains aqueous humor from the anterior chamber into the ocular venous system.

  • Lens - transparent structure located behind the iris that helps focus light onto the retina; also responsible for accommodation (focusing at near). Located behind the iris. A cataract is an opacification of the lens.

  • Ciliary body - ring structure that sits behind the iris. Produces aqueous humor and suspends the Lens via filaments called Zonules.

  • Posterior chamber- the space between the iris and the lens

  • Vitreous chamber - the space between the lens and the retina

  • Vitreous humor - thick, jelly-like transparent substance that fills the vitreous chamber

  • Retina- tissue that lines the inner back wall of the eye, contains photoreceptors and interneurons that absorb light and convert it into visual electrochemical signals

  • Macula - area of the retina responsible for central vision. The fovea is the center of the macula.

  • Choroid - highly vascularized layer of tissue posterior to the retina

  • Optic disc - head of the optic nerve; the optic nerve is composed of the axons of the retinal ganglion neurons, transmitting visual electrochemical signals from the retina to the brain.

  • Uvea - iris + ciliary body + choroid. These 3 tissues are actually connected and collectively make up the vascular layer of the eye.

  • The Anterior segment - all structures that make up the “front” of the eye, i.e., anterior to the vitreous chamber (cornea, iris, iridocorneal angle, lens, ciliary body, aqueous humor)

  • The Posterior segment - all structures that make up the “back” of the eye, i.e., the vitreous chamber and all structures contained within it (vitreous humor, retina, choroid, optic nerve)