Accommodative Intraocular Lens: An intraocular lens implant that’s designed to function similar to the natural eye. After surgical insertion the eye is intended to focus on near, intermediate and far objects. The purpose of this lens is to lessen or eliminate dependence on glasses.Amblyopia (Lazy Eye): A disorder of the coordination between the eye and the brain, usually beginning in childhood that causes the body to prefer one eye over the other, leading to unequal vision.
Aniridia: A congenital condition in which the iris is absent or partially absent. May also result from trauma to the eye.
Anterior Chamber: The space in front of the iris and behind the cornea.
Aqueous Humor: Clear, watery fluid that flows between the lens and cornea and nourishes them.
Astigmatism: A condition that occurs when an uneven curvature of the eye causes light to be refracted (bent) unevenly, resulting in distorted vision.
Automated Lamellar Keratoplasty: A refractive surgery procedure used to treat relatively high degrees of myopia and some cases of hyperopia. This procedure uses only the microkeratome and is not as accurate as the laser procedures that are currently available.
Binocular Vision: The blending of separate images seen by each eye into a single image, allowing images to be seen with depth perception.
Blepharitis: A chronic inflammatory condition of the eyelids, common in children and adults, which causes redness, burning, itching, swollen and crusty lid margins and dry-eye symptoms.
Blind Spot: A small area of the retina where the optic nerve enters the eye which occurs normally in eyes, or a gap in the visual field corresponding to an area of the retina where no visual cells are present.
Bowman’s Membrane: The micro-thin second layer of the cornea that lies just below the epithelium, or outer layer.
Cataract: A gradual opacity or clouding of the normally clear crystalline lens of the eye, caused by the natural aging process, metabolic changes, injury, various forms of radiation, toxic chemicals and certain drugs.
Central Retinal Artery: The blood vessel that supplies nourishment to the retina.
Choroid: The layer filled with blood vessels that nourish the retina.
Ciliary Muscles: The muscles that relax the zonules to enable the lens to change shape for focusing.
Ciliary Processes: The extensions or projections of the ciliary body that secrete aqueous humor.
Collagen: Protein fibrils within the corneal tissue that help sustain its shape.
Concave Lens: A prescription lens that is curved to correct for a cornea that is too convex in shape, resulting in nearsightedness.
Cones and Cone Cells: Specialized, light-sensitive cells (photoreceptors) in the retina that provide sharp central vision and color vision.
Conjunctivitis: An inflammation of the eye’s outer membrane, which causes redness, swelling, itching and watering in one or both eyes.
Contrast Sensitivity: The ability to perceive differences between an object and its background.
Convex Lens: A prescription lens, shaped like a discus, to treat farsightedness by correcting for a cornea that is too concave, or flat.
Cornea: The outer, transparent, dome-like structure that covers the iris, pupil and anterior chamber and serves as part of the eye’s focusing system.
Corneal Disease (Keratitis): A deep infection and inflammation of the cornea caused by an abrasion, inflammation or the presence of bacteria or fungi in the cornea.
Corneal Ulcer: A condition of the cornea that occurs when localized tissue has eroded, usually causing a red, painful eye.
Diabetic Retinopathy: A complication of diabetes in which the blood vessels in the eye become diseased, and may cause vision loss.
Dilation: A process by which the pupil is temporarily enlarged with special eye drops to allow examination of the interior of the eye.
Diopter: A unit of measurement used to describe the degree of refractive error with respect to nearsightedness, farsightedness and astigmatism.
Drusen: Small, yellow or white deposits in the retina or optic nerve head.
Dry Eye Syndrome: A condition caused by the reduction in quality and quantity of tears. For additional information on Dry Eye Syndrome, please see the Dry Eye topic under About Your Eyes.
Ectropion: A condition that occurs when the lower eyelid turns outward, which may result in dry eye symptoms and excessive tearing.
Endothelium: A thin layer of cells lining the undersurface of the cornea that pump fluid from the cornea, keeping it clear.
Entropion: A condition in which the lower eyelid turns inward, causing irritation and may lead to serious infection.
Flashes and Floaters: A condition that occurs when the back of the eye, filled when a jelly-like substance (vitreous gel), becomes increasingly more liquid-like in nature, causing small particles, called floaters, to become visually evident. Flashes originate from the tugging on the retina as the vitreous gel liquefies.
Fluorescein Angiography: A test to examine blood vessels in the retina, choroid and iris in which a special dye is injected into a vein in the arm and photographic images are created as the dye passes through blood vessels in the eye.
Focal Point/Focus: The refraction of light rays by the cornea and the inner lens to a focal point on the retina in a precise, natural manner that produces sharp, clear and colorful images.
Fovea: The central part of the macula that provides the sharpest vision.
Fundus: The interior lining of the eye, including the retina, optic disc and macula, which can be seen during an eye examination by looking through the pupil.
