| a b c d e f g h i j k l m n o p r s t u v w y z |
| a Abrasion, corneal abrasion: Scraped area of corneal surface. Accommodation: Increase in optical power by the eye in order to maintain a clear image as objects are moved closer. After-image: Image that continues to be seen following exposure of one or both eyes to a bright light. Amblyopia: "lazy eye". Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways. Usually is not correctable by optical means (eyeglasses). Applanation: Method of flattening the cornea. Used for measuring intraocular pressure. Aqueous: Clear, watery fluid that fills the space between the back surface of the cornea and the front surface of the vitreous. Artificial tears: Eyedrop that approximates the consistency of normal tears. Astigmatism: Optical defect in which refractive power is not uniform in all directions. Automated lamellar keratoplasty: Excision of the outer corneal layers with a computer controlled Keratone, usually as a part of a refractive keratoplasty procedure. |
| b Base curve: Referring to the curvature of the back surface of a spectacle or contact lens. Bifocals: Eyeglasses that incorporate two different powers in each lens, most of the time for near and distance corrections. Blepharitis: Inflammation of the eyelids, usually with redness, swelling and itching. Blind spot: Adaptive mechanism for avoiding double vision that may accompany an inward eye deviation. Deviation increases until the image falls on the optic disc of the deviated eye, which eliminates double vision. |
| c Capsule, lens capsule: Elastic bag enveloping the eye's crystalline lens. Helps control the shape of the lens for accommodation. Capsulectomy: Removal of part of the lens capsule. Anterior capsulectomy is a routine part of extracapsular cataract extraction. Capsulotomy: Incision to open the lens capsule. Cataract: Opacity or cloudiness of the crystalline lens, which may prevent a clear image from forming on the retina. Surgical removal of the lens may be necessary if visual loss becomes significant, with lost optical power replaced with an intraocular lens, contact lens or aphakic spectacles. May be congenital or caused by trauma, disease or age. Conjunctivitis: Inflammation of the conjunctiva. Characterized by discharge, grittiness, redness and swelling. Usually viral in origin, may be contagious. Cornea: Transparent front part of the eye that covers the iris, pupil and anterior chamber and provides most of an eye's optical power. The cornea has five layers: epithelium, Bowman's membrane, stroma, Decemet's membrane and endothelium. Counts fingers: Patient's ability to count number of fingers presented, usually at a distance of 1 or 2 ft. Administered when vision loss is profound (acuity less than 20/400) |
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d Dystrophy: Progressive changes in a tissue or organ that may result from defective metabolism. |
| e Endothelium: Single-cell layer of tissue lining the innermost surfaces of many organs, glands, and blood vessels; also lines undersurface of the cornea, where it regulates corneal water content. Entropion: Inward turning of upper or lower eyelid so that the lid margin rests against and rubs the eyeball. Enucleation: Removal of the eyeball, leaving eye muscles and remaining orbital contents intact. Episclera: Outermost layer of sclera, composed of loose, fibrous, elastic tissue. Episcleritis: Inflammation of the episclera, outermost layer of the sclera. Affected eye is painful and light sensitive. Epithelium: Membranous multicellular layer covering the internal and external surfaces of the body and its organs. In the eye, covers the cornea, conjunctiva and eyelid. Esotropia: Eye misalignment in which one eye deviates inward while the other fixates normally. Present even when both eyes are covered. Evisceration: Removal of contents of an eyeball, leaving the scleral shell and sometimes the cornea intact. Usually for reducing pain in a blind eye. Excimer laser: Class of ultraviolet lasers, which is almost universally used for photorefractiver keratectomy (PRK). Exotropia: Eye misalignment in which one eye deviates outward while the other fixates normally. |
| f Farsightedness: Also known as hypermetropia or hyperopia. Refractive error. Condition in which eye is underpowered, so that light rays coming from a distant object strike the retina before coming to sharp focus. Focal point: Position on principal axis of lens system where parallel light rays are brought to a point focus. Fundus: Interior surface of eyeball, including retina, optic disc, macula and posterior pole. |
| g Glaucoma: Group of diseases characterized by increased intraocular pressure resulting in damage to the optic nerve and retinal nerve fibers; documented by typical visual field defects and increased size of optic cup. A common cause of preventable vision loss. Goniolens: Specialized contact lens used for examination of anterior chamber angle structures. Granuloma: Lump of tissues consisting of specific types of inflammatory cells; usually associated with some type of infective process. |
| h Halo: Hazy ring around bright lights seen by some patients with refractive error of optical defects. Hand movement: Assessment of low level visual acuity, tested by movement of a waving hand at a specified distance, usually 1 ft or less. Administered when vision loss is so profound the patient cannot see well enough to count fingers. Herpetic keratitis: Eye infection from herpes simplex virus. Results in recurrent episodes of corneal epithelial inflammation with branch like lesions. Heterotropia: Misalignment of eyes caused by extraocular muscle imbalance. Hollenhorst plaques: Orange-yellow cholesterol changes usually found at branching sites of retinal arterioles, rarely cause blood vessel blockage. Associated with server atherosclerosis of the carotid arteries. Hyperopia: Condition in which an eye is underpowered. Thus light rays coming from a distant object strike the retina before coming to sharp focus. True focus is said to be "behind the retina. Hypotropia: downward deviation of one eye while the other remains straight and fixates normally. |
| i Implant: refers to plastic or glass sphere placed in eye socket after surgical removal of an eyeball. Implant (intraocular), intraocular lens, IOL: Plastic lens that may be surgically implanted to replace eye's natural lens. Infection: Invasion of disease-producing microorganisms, resulting in localized cell injury, toxin excretion, or antigen-antibody reaction. Infiltrate: Abnormal accumulation of cells and fluid into tissue where they are not normally found. Intraocular pressure (IOP): 1) Fluid pressure inside the eye. 2) Assessment of pressure inside the eye using a tonometer. Iridotomy: Puncture-like opening made through the iris without removal of any iris tissue. Allows aqueous to drain freely from the posterior chamber to the anterior chamber. Iris: Pigmented tissue lying behind the cornea that (1) gives color to the eye and (2) controls the among of light entering the eye by varying size of the black pupillary opening. Iritis: Inflammation of the iris. Can cause pain, tearing blurred vision, small pupil and a red congested eye. Ishihara test plates: Colored dots that appear as identifiable numbers or patterns to individuals with various types of color vision defects. Used for color vision evaluation. |
| j Jones tube: Glass tube that is inserted into the conjunctiva through orbital bone and into nose to permit tear drainage |
| k Keratectomy: Removal of a piece of the cornea. Keratitis: Corneal inflammation characterized by loss of luster and transparency, and cellular infiltration. Keratoconus: Hereditary degenerative corneal disease characterized by generalized thinning and cone shaped protrusion of central corneal. Usually affects vision of both eyes and occurs during 2nd decade of life. Keratome: Any knife designed to make a corneal incision. Keratometer: Device for measuring corneal curvature and for detecting and measuring astigmatism. Keratoplasty (corneal graft or transplant): Replacement (transplantation) of scarred or diseased cornea with clear corneal tissue from a donor. |
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l Lens: (1) Natural, crystalline lens of eye: transparent, biconvex intraocular tissue that helps bring rays of light to focus on the retina. Suspended by fine ligaments attached between ciliary processes. (2) Any piece of glass or other transparent material with ability to bend light rays predictably. |
| m Macula: "Yellow Spot". Small, specialized central area of the retina, surrounding the fovea; responsible for acute central vision. Macular degeneration: One of the most common causes of decreased vision after age 60. Usually evident as a loss of pigment from pigment epithelium and deposits of yellowish material in the sub-pigment epithelial layer in the central retinal zone. Miotic: (1) Refers to small pupils. (2) Chemical that reduces size of pupils by stimulating parasympathetic nervous system or by blocking sympathetic nervous system. Mires: Focusing guides on an optical instrument that aid in measurement. |
| n Nearsightedness, myopia: Overpowered eye in which parallel light rays from a distant object are brought to focus in front of the retina. Requires minus lens correction to "weaken" eye optically and permit clear distance vision. Nevus: Mole; small, flat, usually pigmented benign tumor made up of specific cells called nevus cells; found in skin and eye tissues. Night blindness, nyctalopia: Inefficient dark adaptation that results in markedly reduced vision in dim illumination. Nuclear sclerosis: Type of early cataract characterized by increasing hardness or density at the center of the eye's crystalline lens. |
| o Occluder: Device used for covering one eye during testing or treatment. Ocularist: Professional trained to design and fit artificial eyes. Oculoplastic surgery: Subspecialty of ophthalmology dealing with diseases and reconstructive aspects of the eyelids. Open angle glaucoma: Most common type of glaucoma. Associated with increased intraocular pressure. Ophthalmologist: Physician specializing in refractive, medical and surgical treatment of eye diseases and disorders. Ophthalmology: Deals with the eye, its function and diseases. Includes diagnosis and management. Opthalmoscope: Device used for examining the interior of the eye, especially the fundus (retina). Optometrist: Non-medical professional trained to prescribe eyeglasses or contact lenses, examine eyes and detect eye disease. Orbit: Pyramid-shaped cavity in the skull, about 23 inches deep and lined by the orbital bones. Contains the eyeball, its muscles, blood supply, nerve supply and fat. |
| p Pachometer: Device that uses optical principle of split images to measure corneal thickness or anterior chamber depth. Phoropter: Refraction device combining a large variety of spherical and cylindrical lenses, prisms, occludes and pinholes. Used for determining an eye's optical correction. Photophobia: Abnormal sensitivity to and discomfort from light. Pneumotonometer: Gas-pressurized device that measures intraocular pressure by blowing a puff of air against the cornea to flatten it slightly. Prism: Triangular, wedge-shaped, transparent medium that bends, but does not focus, light rays toward the position of its base. Prosthesis: "False Eye"; Plexiglas shell painted to resemble a natural eye. Cosmetic replacement after removal of eye. Ptosis: Drooping of upper eyelid. May be congenital or caused by paralysis or weakness or 3rd cranial nerve or sympathetic nerves, or by excessive weight of upper lids. Punctal plug: Plastic materials inserted into punctum to prevent normal tear drainage so as to preserve tears for moistening cornea and conjunctiva. Punctum: Opening in lacrimal canaliculi, located on the upper and lower eyelid margin near the nose. Entrance to the tear drainage system from eye surface into nose. Pupil: Variable-sized black circular opening in center of iris; regulates amount of light that enters eye. |
| r Radial keratotomy: eight to 16 radical cuts made in the periphery of the cornea to allow the central cornea to flatten, reducing its optical power and thereby near-sightedness. Reflection: Bouncing back of light rays by a mirror like surface. Refraction: Bending of light rays as they travel from a clear medium of one density to another of different density. Retina: Part of eye that converts images from the eye's optical system into electrical impulses sent along the optic nerve for transmission to the brain. Retinal detachment: Separation of sensory retina from underlying pigment epithelium. Disrupts visual cell structure and thus markedly disturbs vision. Almost always caused by a retinal tear. Retinoscope: Hand-held device for measuring an eye's refractive error, with no verbal response required from the patient. Retrobulbar neuritis: Optic nerve inflammation that occurs behind the optic disc within the orbit so that no early disc changes are visible in the eye. |
| s Schematic eye: Simplified optical and mechanical model of the eye, used in teaching retinoscopy and optical fundamentals. Schirmer test: For measuring quantity of tear production. Scleral buckle: Used in repair of a retinal detachment; the sclera is indented or buckled inward, usually by sewing a piece of preserved sclera or silicone rubber to its surface. Scleral flap: Section of sclera that has been dissected on 2 or 3 sides, used to expose the deeper sclera or inside of eye. Scotoma, blind spot: Non-seeing pathways or retina. A physiologic blind spot exists normally and marks the site of the optic nerve. Slab-off: Grinding of lower part of spectacle lens. Helps compensate for a lens induced vertical prism power that occurs with unequal refractive errors in the two eyes. Snellen chart: for assessing visual acuity. Rows of letters, numbers, or symbols in standardized graded sizes, with a designated distance which each row should be legible to a normal eye. Usually tested at 6 m (20ft). Spectacles: Eyeglasses. Spherical equivalent: "Average" power of a toric lens, equal to the sum of the spherical power plus half the cylindrical power. Strabismus: Eye misalignment caused by extraocular muscle imbalance: one fovea is not directed at same object as the other. Subconjunctival hemorrhage: Bleeding from a small blood vessel under the conjunctiva. Often spontaneous or can occur from coughing. It creates a harmless but striking bright-red blood appearance over the sclera. Blood absorbs in about 1 week without treatment. |
| t Tarsus: Dense, plate-like framework within upper and lower eyelids that provides stiffness and shape. Tear duct: Tear drainage channel that extends form the lacrimal sac to an opening in the mucous membrane of the nose. Tonometer: Device that measures intraocular pressure. Tropia: Eye misalignment caused by extraocular muscle imbalance: one fovea is not directed at same object as the other. 20/20: Normal visual acuity. Upper number indicates that a patient is able to see standardized symbols on a chart 20 ft (6m) away; lower number indicates that the same symbols can be seen at 20ft by an eye with a normal optical system. |
| u Ulcer, corneal ulcer: Area of epithelial tissue loss form corneal surface. Associated with inflammatory cells in the cornea and anterior chamber. Usually caused by a bacterial, fungal or viral infection. Upper punctum: Dimple-like opening in the upper eyelid margin near the nose. Marks the upper entrance to the eye's tear drainage system. Uvea: Pigmented layers of eye (iris, ciliary body, choroid) that contain the majority of the blood vessel supply. |
| v Viral conjunctivitis: "Pink Eye" Viral inflammation of the conjunctiva which is the mucous membrane that covers white of the eye and inner eyelid surfaces. Characterized by discharge, grittiness, redness and swelling. Usually contagious. Vision: Ability of the eye to receive, resolve, and transmit light images to the brain's occipital lobe, where the light sensation is interpreted. Vitreous: Transparent, colorless, gelatinous mass filling the rear two-thirds of interior of the eyeball between the lens and the retina. |
| w White of the eye: (Sclera). Opaque, fibrous, protective outer layer of the eye containing collagen and elastic fibers. Directly continuos with cornea in front and sheath covering optic nerve behind. Worth four-dot test (W4d): Test that evaluates capacity of the two eyes to perceive images simultaneously. Patient view 4 lights (1 red, 1 white, 2 green) through a red filter before one eye and a green filter before the other. |
| y YAG laser: Short pulsed, high-energy light beam that can be precisely focused by computer to cut, perforate, or fragment tissue. |
| z Zonules: Radially arranged fibers that suspend the lens from the ciliary body and hold it in position. Zygoma: Cheek bone; forms part of the orbital floor and most of the lateral wall. One of 7 bones of the orbit. Zygomatic nerve: Branch of maxillary nerve that supplies sensation to facial skin below lower eyelid and temporal region. Enters the orbit through the inferior orbital fissure, divides into zygomatico-temporal and zygomatico facial branches, and exits through canals in the zygoma. |
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