Medical Terminology

The Eye Medical Center is happy to provide you with a list of terms in order for you to keep informed.

Abrasion, corneal abrasion. Injury. Scraped area of corneal surface; accompanied by loss of superficial tissue (epithelium).

Age-related macular degeneration (AMD, ARMD) (MAK-yu-lur), macular (or) senile macular degeneration. Pathologic condition. Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision. Two general types: "dry," which is usually evident as a disturbance of macular pigmentation and deposits of yellowish material under the pigment epithelial layer in the central retinal zone; "wet," (sometimes called Kuhnt-Junius disease) in which abnormal new blood vessels grow under the retina and leak fluid and blood further disturbing macular function. Most common cause of decreased vision after age 60.

Allergic conjunctivitis. Pathologic condition. Hypersensitivity of the conjunctiva (membrane covering white of eyes and inner lids) to foreign substances. Characterized by discharge, itching, irritation, swelling, tearing, redness, and light sensitivity. The discharge contains a large number of white blood cells (eosinophils).

Amblyopia (am-blee-OH-pee-uh), "lazy eye." Functional Defect. Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways. Usually uncorrectable by optical means (e.g., eyeglasses).

Anterior chamber (AC). Anatomy. Fluid-filled space inside the eye between the iris and the innermost corneal surface (endothelium).

Astigmatism (uh-STIG-muh-tiz-um). Refractive error. Optical defect in which refractive power is not uniform in all directions (meridians). Light rays entering the eye are bent unequally by different meridians, with maximum and minimum powers 90 degrees to one another, which prevents formation of sharp point focus on the retina. Instead, light rays form two focal lines separated by a focal zone. Usually results from corneal asphericity. Corrected by a cylindrical (toric) eyeglass or contact lens.

Bandage lens. Optical device. Soft contact lens with no refractive power, used for protecting damaged or irregular corneal surfaces.

Bifocals. Optical device. Eyeglasses that incorporate two different powers in each lens, usually for near and distance corrections.

Blepharitis (blef-uh-RI-tus). Pathologic Condition. Inflammation of the eyelids, usually with redness, swelling and itching. Many causes, e.g., infection, allergy.

Cancer, malignant lesion. Pathologic condition. Tissue of potentially unlimited growth that expands locally by invasion, and throughout the body by metastasis.

Cataract. Pathological condition. Opacity or cloudiness of the crystalline lens, which may prevent a clear image from forming on the retina. Surgical removal of 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.

Chalazion (kuh-LAY-zee-un). Pathologic condition. Inflamed lump in a meibomian gland (in the eyelid). Inflammation usually subsides, but may need surgical removal. Sometimes called an internal hordeolum. Plural: chalazia.

Choroid (KOR-oyd), Anatomy. Vascular (major blood vessel) layer of the eye lying between the retina and sclera. Provides nourishment to outer layers of the retina. Forms part of the uvea, along with the ciliary body and iris.

Conjunctivitis (kun-junk-tih-VI-tis), "pink eye." Pathologic Condition. Inflammation of the conjunctiva (mucus membrane that covers white of eye and inner eyelid surfaces). Characterized by discharge, grittiness, redness and swelling. Usually viral in origin; may be contagious.

Contact arc, arc of contact. Anatomy. Distance between an extraocular muscle's initial point of contact with the sclera and its true insertion on the eyeball.

Contact lens. Optical Device. Small plastic disc containing optical correction, worn on the cornea or sclera as substitute for eyeglasses.

Corneal ulcer. Pathologic condition. Area of epithelial tissue loss from the corneal surface. Associated with inflammatory cells in the cornea and anterior chamber. May be caused by bacterial, fungal, or viral infection.

Cycloplegic refraction. Test. Assessment of an eye's refractive error after lens accommodation has been paralyzed with cycloplegic eye drops (to eliminate variability in optical power caused by a contracting lens).

Cyst. Anatomy. Thin walled sac, usually containing a liquid or a semisolid. May be normal or abnormal.

Cystoid macular edema (CME) (SIS-toyd MAK-yu-lur). Pathologic condition. Retinal swelling and cyst formation in the macular area; usually results in temporary decrease in vision, though may be permanent. Frequently occurs to some extent after cataract surgery. Specific cause is unknown.

Cytomegalovirus (CMV) (SI-toh-meg-al-oh-VI-rus). Pathologic condition. Large virus commonly present in the urinary tract. Rarely causes disease unless the individual is immunosuppressed (has poor immune response), e.g., in AIDS, in which case it can cause serious disease, e.g., CMV retinitis.

Diabetic retinopathy (ret-in-AHP-uh-thee). Pathologic condition. Spectrum of retinal changes accompanying long-standing diabetes mellitus. Early stage is background retinopathy, which includes the growth of abnormal new blood vessels (neovascularization) and accompanying fibrous tissue.

Dilate (DI-layt). Function, procedure. To widen an opening, such as the pupil or lacrimal punctum.

Dilated pupil. Anatomic change. Enlarged pupil, resulting from contraction of the dilator muscle or relaxation of the iris sphincter. Occurs normally in dim illumination, or may be produced by certain drugs (mydriatics) or result from blunt trauma.

Diopter (D) (di-AHP-tur). Unit of measure. Unit to designate the refractive power of a lens, or the degree of light convergence or divergence. Equal to the reciprocal of a lens' focal length (in meters), e.g., a 2-diopter lens brings parallel rays of light to a focus at ½m.

Diplopia, double vision. Functional defect. Perception of two images from one object; images may be horizontal, vertical or diagonal.

Dry eye syndrome, keratitis sicca, keratoconjunctivitis sicca. Pathologic condition. Corneal and conjunctival dryness due to a deficient tear production predominantly in menopausal and post-menopausal women. Can cause foreign body sensation, burning eyes, filamentary keratitis, and erosion of conjunctival and corneal epithelium.

Ectropion (ek-TROH-pee-un). Pathologic condition. Outward turning of the upper or lower eyelid so that the lid margin does not rest against the eyeball, but falls or is pulled away. Can create corneal exposure with excessive drying, tearing, and irritation. Usually from aging. See also ENTROPION.

Endophthalmitis (een-dahf-thal-MI-tus). Pathologic condition. Inflammation of tissues inside the eyeball. Usually refers to purulent intraocular infection.

Entropion (en-TROH-pee-un). Anatomic Defect. Inward turning of upper and lower eyelid so that the lid margin rests against and rubs the eyeball. See also ECTROPION.

Esotropia (ET) (ee-soh-TROH-pee-uh), Convergent deviation, cross-eyes, internal strabismus. Functional defect. Eye misalignment in which one eye deviates inward (toward nose) while the other eye fixates normally. Present even when both eyes are covered.

Exotropia (XT) (eks-oh-TROH-pee-uh), divergent (or) external strabismus, wall-eyes. Functional defect. Eye misalignment in which one eye deviates outward (away from nose) while the other fixates normally.

Eye examination. Evaluation that usually includes any or all of the following: visual acuity for distance and near (with and without correction), intraocular pressure, pupil functions, checks for external and internal infection, disease or defects, extraocular muscle function, inspection of lens and retina through a dilated pupil, plus others.

Floaters, vitreous floaters. Anatomic defect. Particles that float in the vitreous and cast shadows on the retina; seen as spots, cobwebs, spiders, etc. Occurs normally with aging or with vitreous detachment, retinal tears, or inflammation.

Gas permeable lens (GP), rigid gas permeable lens. Optical device. Rigid plastic contact lens that allows oxygen and carbon dioxide penetration. See also HARD CONTACT LENS, SOFT CONTACT LENS.

Glaucoma (glaw-KOH-muh). Pathologic condition. 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 cut. A common cause of preventable vision loss. May be treated by prescription drugs or surgery.

Graves' disease, Basedow's disease, endocrine (or) Graves' exophthalmos (or) ophthalmopathy, thyroid eye disease, thyrotoxic (or) thyrotropic exophthalmos. Pathologic condition. Eye signs that may occur with excessive thyroid-related hormone concentration. Includes eye-lid retraction, eyelid lag on downward gaze, corneal drying, eye bulging (proptosis), fibrotic extraocular muscles, and optic nerve inflammation.

Hard contact lens (HCL). Optical device. Rigid plastic lens that floats on the corneal tear film. Usually made of polymethyl methacrylate (PMMA). See also GAS PERMEABLE LENS, SOFT CONTACT LENS.

Herpes simplex virus (HSV). Microorganism. Virus that infects the nerves in the skin and mucous memebranes. In the cornea it produces painful branch-like ulcers (dendritic keratitis). Frequently recurrent, causing corneal opacification.

Herpes zoster, shingles. Pathologic condition. Extremely painful, blister like skin lesions on the face, sometimes with inflammation of the cornea, sclera, ciliary body and optic nerve. Affects the 1st division (ophthalmic nerve) of the 5th (trigeminal) cranial nerve. Caused by the chickenpox virus.

Hyperopia (hi-pur-OH-pee-uh), farsightedness, hypermetropia. Refractive error. Focusing defect 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." Corrected with additional optical power, which may be supplied by a plus lens (spectacle or contact) or by excessive use of the eye's own focusing ability (accommodation).

Intraocular lens: see IOL.

IOL (intraocular lens), implant, pseudophakos. Optical device. Plastic lens that may be surgically implanted to replace the eye's natural lens.

Keratitis (KEHR-uh-TI-tis). Pathologic condition. Corneal inflammation, characterized by loss of luster and transparency, and cellular infiltration.

Keratoconus (kegr-uh-toh-KOH-nus). Pathologic condition. Degenerative corneal disease affecting vision. Characterized by generalized thinning and cone-shaped protrusion of the central cornea, usually in both eyes. Becomes apparent during 2nd decade of life. Hereditary.

LASIK (LAY-sik). Surgical procedure. Acronym: Laser in Situ Keratomileusis, also Laser Assisted Intrastromal Keratoplasty. Type of lamellar refractive surgery in which the cornea is reshaped to change its optical power. A disc of cornea ("button") is raised as a flap, then an excimer laser is used to reshape the intrastromal bed, producing surgical flattening of the cornea. Used for correcting very high refractive errors, especially myopia. (Differs from keratomileusis, in which reshaping is done by lathe-cutting the corneal button.)

Lens Anatomy. Natural crystalline lens of the eye. Transparent, biconvex intraocular tissue that helps bring rays of light to focus on the retina. Suspended by fine ligaments (zonules) attached between ciliary processes.

Lens Optics. Any piece of glass or other transparent material that can bend light rays predictably.

Low-vision aids (LVA). Optical device. High-powered plus lenses and telescopes with high magnification, to help patients who have poor vision.

Macular degeneration (ARMD, AMD), age-related (or) senile macular degeneration. Pathologic condition. Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision. Two general types: "dry," which is usually evident as a disturbance of macular pigmentation and deposits of yellowish material under the pigment epithelial layer in the central retinal zone; and "wet" (sometimes called Kuhnt-Junius disease), in which abnormal new blood vessels grow under the retina and leak fluid and blood, further disturbing macular function. Most common cause of decreased vision after age 60.

Manifest refraction (M), refined refraction. 1. Test. Presentation of a series of test lenses in graded powers to determine without using eye drops (cycloplegics) which corrective lenses provide the sharpest, clearest vision. 2. Prescription for eyeglasses or contact lenses resulting from this test.

Melanoma (meh-luh-NOH-muh). Pathologic condition. Malignant tumor derived from pigment cells. In the eye, can initiate in the choroids, ciliary body or iris, though any eye tissue can be affected by metastases or invasive growth from a melanoma elsewhere in the body.

Myopia (mi-OH-pee-uh), nearsightedness. Refractive error. Focusing defect in which the eye is overpowered. Light rays coming from a distant object are brought to focus in front of the retina. Requires a minus lens correction to "weaken" the eye optically and permit clear distance vision.

Normal Optics. Line perpendicular to the surface of a medium.

Nystagmus (ni-STAG-mus), jerk nystagmus. Functional defect. Involuntary, rhythmic side-to-side or up and down (oscillating) eye movements that are faster in one direction than the other.

Optic atrophy (AT-roh-fee). Pathologic condition. Optic nerve degeneration characterized by optic disc paleness. Usually results in irreversible loss of vision.

Optic neuritis. Pathologic condition. Inflammation of the optic nerve. May accompany demyelinating disease (e.g., multiple sclerosis) or infections from the meninges, orbital tissues or paranasal sinuses. Characterized by rapid onset of decreased vision and, usually, discomfort with eye movement and a central visual field defect.

Peripheral vision. Function. Side vision; vision elicited by stimuli falling on retinal areas distant from the macula.

Pinguecula (pin-GWEK-yu-luh). Anatomic defect. Yellowish-brown subconjunctival elevation composed of degenerated elastic tissue; may occur on either side of the cornea. Benign. Plural: pingueculae. See also PTERYGIUM.

"pink eye," conjunctivitis. Pathological condition. Inflammation of the conjunctiva (mucous membrane covering white of eye and inner eyelid surfaces). Characterized by discharge, grittiness, redness and swelling. Usually viral in origin; may be contagious.

Plano (PLAY-noh). Optics. Lens that has no focusing power, neither plus nor minus.

Posterior capsulotomy (kap-sul-AH-tuh-mee). Surgical procedure. Opening in the rear lens capsule when it has become opacified after previous cataract surgery; usually made with a YAG laser.

Presbyopia (prez-bee-OH-pee-uh). Functional defect. Refractive condition in which there is a diminished power of accommodation arising from loss of elasticity of the crystalline lens, as occurs with aging. Usually becomes significant after age 45.

Progressive addition lens. Optical device. Type of near-vision eyeglass lens designed so that power for near increases gradually from zero (in center) to maximum add (lower portion) with no telltale bifocal demarcation line.

Pterygium (tur-I-jee-um). Pathologic condition. Abnormal wedge-shaped growth on the bulbar conjunctiva. May gradually advance onto the cornea and require surgical removal. Probably related to sun irritation. Plural: pterygia. See also PINGUECULA.

Ptosis (TOH-sis), blepharoptosis. Functional defect. Drooping of upper eyelid. May be congenital or caused by paralysis or weakness (paresis) of the 3rd (oculomotor) cranial nerve or sympathetic nerves, or by excessive weight of the upper lids.

Punctual plug. Surgical device. Plastic materials (polyhydroxethyl methacrylate or silicone) inserted into the punctum to prevent normal tear drainage, to preserve tears for helping keep the cornea and conjunctiva moist.

Rapid eye movements (REM). Function. Bursts (about 1 min. each) of fast eye movements that occur periodically during sleep. Associated with dreams.

Recurrent corneal erosion. Pathologic condition. Episodic, periodic loss of the outer layer of cornea (epithelium) due to its failure to adhere properly to Bowman's membrane; extremely painful. May follow minor scratch-type injury.

Refractive error. Functional defect. Optical defect in an unaccommodating eye; parallel light rays are not brought to a sharp focus precisely on the retina, producing a blurred retinal image. Can be corrected by eyeglasses or contact lenses.

Refractive surgery, keratorefractive surgery. Surgical procedure. Various procedures that alter the shape of the cornea and thus how it bends light, in order to change the eye's refractive error. Can reduce or eliminate the need for spectacle or contact lens correction. Procedures include arcuate keratotomy, epikeratophakia, keratomileusis, keratophakea, laser sculpting, LASIK, photorefractive surgery, radial keratotomy, refractive keratoplasty, thermoplasty, transverse keratotomy.

Reiter's syndrome (Ri-turz). Pathologic condition. Arthritis, urethritis, and conjunctivitis or iritis. Unknown cause.

Retinal detachment (RD), retinal separation. Pathologic condition. Separation of sensory retina from the underlying pigment epithelium. Disrupts visual cell structure and thus markedly disturbs vision. Almost always caused by a retinal tear; often requires immediate surgical repair.

Retinitis (reh-tin-I tis). Pathologic condition. Inflammation of the retina.
r. pigmentosa (RP): progressive retinal degeneration in both eyes. Night blindness, usually in childhood, is followed by loss of peripheral vision (initially as ring-shaped defect), progressing over many years to tunnel vision and finally blindness. Hereditary.

Retinoblastoma (ret-in-noh-blas-TOH-muh). Pathologic condition. Malignant intraocular tumor that develops from retinal visual cells. If untreated, seedling nodules produce secondary tumors that gradually fill the eye and extend along the optic nerve to the brain, ending in death. Most common childhood ocular malignancy. Hereditary.

Retinopathy (ret-in-AHP-uh-thee). Pathologic condition. Non-inflammatory degenerative disease of the retina.
r. of prematurity (ROP): series of destructive retinal changes that may develop after prolonged life-sustaining oxygen therapy is given to premature infants. In the active stage, findings include dilated, tortuous peripheral blood vessels, retinal hemorrhages and abnormal newly formed blood vessels (neovascularization). Sometimes regresses; other times a peripheral fibrotic scar forms that detaches the retina. Can result in vision loss or blindness. Other possible complications: glaucoma, cataracts, myopia (nearsightedness), sunken eyes, eye misalignment. Previously called retrolintal fibroplasias.

Rigid gas permeable lens (RGP), gas permeable lens. Optical device. Rigid plastic contact lens that allows oxygen and carbon dioxide penetration. See also HARD CONTACT LENS, SOFT CONTACT LENS.

Sclera (SKLEH-ruh), tunica fibrosa oculi. Anatomy. Opaque, fibrous, protective outer layer of the eye ("white of the eye") that is directly continuous with the cornea in front and with the sheath covering optic nerve behind. Contains collagen and elastic fibers. Plural: sclerae. Scleral lens. Optical device. Large rigid contact lens used for correcting refractive errors and for protecting some types of diseased corneas. May be molded to fit patient's own cornea and sclera. Rarely used.

Soft Contact Lens (SCL). Optical Device. Water-absorbing (hydrophilic) small plastic disc used for correcting refractive error or protecting a damaged corneal surface. Rests on the cornea; often more comfortable and easier to tolerate than a hard contact lens.

Strabismus (struh-BIZ-mus), deviation, heterotropia, squint, tropia. Functional defect. Eye misalignment caused by extraocular muscle imbalance: one fovea is not directed at the same object as the other. Present even when both eyes are uncovered.

Stroke, cerebrovascular accident. Pathologic condition. Sudden loss of specific brain functions (e.g., speech, specific movement), resulting from interrupted blood supply, as by an embolus, thrombosis or hemorrhage; usually from cerebral blood vessel disease (atherosclerosis).

Stye, sty, external hordeolum. Pathologic condition. Acute pustular infection of the oil glands of Zeis, located in an eyelash follicle at the eyelid margin.

Toric Lens (TOR-ik), sphero-cylindrical lens. Optical device. Lens that has a cylindrical component; used for correcting an astigmatic refractive error. Most eyeglasses are of this type.

Trifocal (TRI-foh-kul). Optical device. Eyeglass lenses of different powers. The main portion is usually focused for distance (20 ft.), the center segment for about 2 ft., and the lower segment for near (14 in.).

Usher's syndrome. Pathologic condition. Retinal pigment epithelium degeneration accompanied by congenital nerve deafness. Hereditary.

Uveitis(yu-vee-l-tis). Pathologic condition. Inflammation of any of the structures of the uvea: iris, ciliary body, or chorid. Plural: uveitides.

Vision. Function. Ability of the eye to receive, resolve and transmit light images to the occipital lobe in the brain, where light sensation is interpreted. "Seeing ability" in its broadest sense.

Visual acuity. Measurement. Assessment of the eye's ability to distinguish object details and shape, using the smallest identifiable object that can be seen at a specified distance (usually 20 ft. or 16 in.).