Accommodation: The process of focusing the lens for close vision.
Aqueous humor: Transparent watery fluid in the anterior segment of the eyeball.
Choroid: The pigmented vascular middle tunic of the eye.
Ciliary body: Anterior portion of the choroid that includes the ciliary muscle and ciliary process.
Conjunctiva: Mucous membrane lining the anterior surface of the eyeball and posterior surface of eyelids; acute contagious conjunctivitis is called pinkeye.
Cornea: Transparent avascular dome forming the anterior part of the sclera of the eyeball.
Fovea centralis: Depression in the center of the macula lutea that contains the greatest density of cones, and is the area of greatest visual acuity.
Iris: Pigmented smooth muscle structure that controls the amount of light entering the eye.
Lacrimal apparatus: Structures that produces and provides drainage for lacrimal fluid (tears).
Lens: Transparent structure posterior to the pupil that changes shape to focus on objects at various distances.
Macula lutea: A yellow oval spot at the center of the retina which absorbs harmful ultraviolet light; it contains only cones and provides sharp, detailed central vision.
Optic disc: The blind spot; area in the retina that lacks photoreceptors and the optic nerve exits the eye.
Photoreceptors: Retinal cells responsible for vision; rod cells detect only black and white, while cone cells detect color.
Pupil: Opening in the center of the iris through which light enters the eye.
Retina: The deep tunic of the eye containing the photoreceptors.
Sclera: The white of the eye; superficial tunic composed of white fibrous connective tissue.
Scleral venous sinus: A sinus located at the junction of the sclera and cornea, where aqueous humor drains from the anterior chamber of the eyeball into the blood. Also called canal of Schlemm.
Suspensory ligaments: Attaches the lens to the ciliary body; allows the lens to change shape.
Tarsal glands: Sebaceous (oil) gland that opens on the edge of each eyelid.
Vitreous body: A transparent jellylike substance that fills the posterior segment of the eyeball, composed of a mesh of protein fibers and vitreous humor.
Vitreous humor: Transparent fluid component of the vitreous body.