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Retina InstituteCornea InstituteEye Birth Defects InstituteOrbit and Eye Movement InstituteVision Development InstituteEye Technology Institute
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Glossary

A - D  ||  E - H  ||  I - L  ||  M - P  ||  Q - T  ||  U - Z



(A - D)

albinism (al-buh-nih-zum). A lack of pigment or color. The eyes may appear reddish or pink because the blood vessels show through the iris, which already lacks in color.
amblyopia (am-blee-OH-pee-uh). Sometimes called "lazy eye," is a condition in which the brain cannot make normal use of the visual information coming from one of the eyes. Usually this is the result of a competition between the eyes at the level of the visual areas of the brain.

     Orbit and Eye Movement Institute
     Vision Development Institute
anisocoria (a-nice'-ah-kor'-e-ah). Unequal pupil sizes.
anisometropia. Power differences between each eye causing a lazy eye or a weaker eye and poor eyesight. The refractive error is different in the two eyes; this can sometimes cause amblyopia (Partial or complete loss of vision in one eye).

     Cornea Institute
     Orbit and Eye Movement Institute
     Vision Development Institute
anterior chamber. Fluid-filled space inside the eye between the iris and the innermost corneal surface (endothelium).

anterior synechia (see-neke'-e-ah). Adhesions between the edge of the pupil and the anterior surface of the lens.
anterior uveitis (u-v-ite' -us). Inflammatory cells suspended in the aqueous humor.
aqueous humor. A clear, watery fluid circulating in the chamber of the eye between the cornea and the lens.

astigmatism. Can be combined with either nearsightedness or farsightedness, and means that the amount of refractive error is different for vertical and horizontal objects.

     Orbit and Eye Movement Institute
     Vision Development Institute
binocular vision. Blending of the separate images seen by each eye into one composite image.

     Orbit and Eye Movement Institute

cataracts. A cataract is a clouding of the lens in the eye that affects vision and can occur in either or both eyes. The most common symptoms of a cataract are blurry vision, faded colors, glare, poor night vision and/or double vision.

     Cornea Institute
coats' disease. A rare eye disorder involving abnormal development of the blood vessels of the retina, which lines the interior chamber of the eye.

     Retina Institute
coloboma. A gap in part of the structures of the eye. This gap can occur in the iris, the retina, or the optic nerve and can be large or small. The most common form of gap is caused by an imperfect closure of a cleft, present in the womb but usually closed by birth. Coloboma of the eye is an important cause of childhood visual impairment and blindness.

     Eye Birth Defects Institute
coloboma of the iris. Keyhole-shaped pupil.
cone. Light-sensitive retinal receptor cell that provides sharp visual acuity and color discrimination.

     Retina Institute
congenital cataract. A lens that is opaque or not clear at birth.
convergence insufficiency. This muscle condition causes the eyes to conflict and drift outward, resulting in strain or blurring, double vision and/or headaches.

     Orbit and Eye Movement Institute
cornea (KOR-nee-uh). The clear "front window" of the eye that transmits and focuses light into the eye. Similar to the lens of a camera, the cornea provides two-thirds of the eye's focusing power. Its five layers must be free of any cloudy or opaque areas to allow proper vision.

     Cornea Institute
cross-eyes. See strabismus.

DeMorsier's Syndrome. See Optic Nerve Hypoplasia (ONH).

dilated pupil. 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, cycloplegics) or result from blunt trauma.

diopter (D) (di-AHP-tur). Unit to designate the refractive power of a lens.

dislocated lens. A lens that is not in its correct position.
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(E-H)

esotropia (ee-soh-TROH-pee-uh), cross-eyes. Eye misalignment in which the eyes are turned inward relative to one another.

     Orbit and Eye Movement Institute
     Vision Development Institute
exotropia (eks-oh-TROH-pee-uh), wall-eyes. Eye misalignment in which the eyes turn outward.

     Orbit and Eye Movement Institute
     Vision Development Institute
extraocular muscles (eks-truh-AHK-yu-lur). Six relatively small muscles – control the movement of the eyes in the socket, allowing them to rotate or turn horizontally and vertically. As such, these muscles play a crucial role in functional, accurate eye movement.

     Orbit and Eye Movement Institute
eyelids. Structures covering the front of the eye, which protect it, limit the amount of light entering the pupil, and distribute tear film over the exposed corneal surface.

eye tumor. A growth or mass that occurs in or next to the eye. See Retinoblastoma.

farsightedness. See hyperopia.

floaters. 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.

glaucoma (glaw-KOH-muh). Group of diseases characterized by increased intraocular pressure resulting in damage to the optic nerve and retinal nerve fibers. Glaucoma is the second leading disease in America resulting in blindness. While it is not curable, it can be controlled if detected and treated early. Increased intraocular pressure may cause irreversible damage to the eye if not controlled. Early detection and treatment are hampered by a lack of symptoms in the initial stages of the disease and by low levels of public awareness and knowledge that regular, comprehensive eye examinations are necessary.

     Cornea Institute
hereditary retinal degeneration. Because of all the complex functions the retina performs, the retina relies on a wide variety of genes to carry out its tasks. Should any one of these genes be lost or mutated, it can have a severe impact on vision.

     Retina Institute
hydrocephalus. An abnormal accumulation of cerebrospinal fluid (CSF) within cavities called ventricles inside the brain. (The word "hydrocephalus" comes from the Greek: "hydro" means water, "cephalus" means head).

     Eye Birth Defects Institute
hyperopia (hi-pur-OH-pee-uh) or farsightedness, is when the eyes are not naturally focused anywhere, not even for far distance. The child has to make special focusing efforts even to see far away, and extra focusing efforts on top of that to see up close.

     Orbit and Eye Movement Institute

hypertropia. Eye misalignment in which the eyes turn upward.

     Orbit and Eye Movement Institute
     Vision Development Institute
hyphema (hi-phe'-ma). Blood or a blood clot(s) in the aqueous humor obscuring the color of the iris following injury or trauma.
hypopituitarism. The underactivity of the pituitary gland, resulting in inadequate hormone production. The development of the pituitary gland, found at the base of the brain, can be affected by optic nerve hypoplasia (ONH). The pituitary gland is the body’s master control gland; it makes and directs important hormones required for growth, energy control and sexual development.

     Eye Birth Defects Institute
hypopyon (hi-pope'-e-an). A white layer of inflammatory cells that have settled out of the aqueous humor onto the surface of the iris and obscures the inferior portion of the iris.
hypotropia. Eye misalignment in which the eyes turn downward.

     Orbit and Eye Movement Institute

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(I-L)

intraocular lens. This plastic polymer lens is surgically implanted to replace the focusing power of the natural lens of the eye following cataract extraction. The Intraocular Lens (IOL) comprises two types of lenses; non-foldable (made of a hard plastic material) and foldable (made of silicone or acrylic).

     Cornea Institute
iris. The circular, colored curtain of the eye, which opens and closes to regulate the amount of light entering the eye.

iris neovascularization. Abnormal vessels growing in the iris.

iritis (i-rite-us). Inflammation of the iris.

laser. High energy light source that uses light emitted by the natural vibrations of atoms (of a gas or solid material) to cut, burn or dissolve tissues for various clinical purposes.

LASIK (LAY-sik). Type of refractive surgery in which the cornea is reshaped to change its optical power. A disc of cornea 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 myopia, hyperopia, and astigmatism.

     Cornea Institute
"lazy eye." See amblyopia.

legal blindness. Best-corrected visual acuity of 20/200 or less, or reduction in visual field to 20¡ or less, in the better seeing eye.

lens. A transparent structure behind the iris that changes shape to focus light rays onto the retina in the back of the eye.

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(M-P)

macula. Small central area of the retina surrounding the fovea; area of acute central vision.

     Retina Institute
morning glory syndrome. A birth defect of the hole in the back of the eye through which the optic nerve exits on its pathway to the brain. This results in a funnel-shaped optic nerve head with the retina dragged into it causing the retinal vessels to radiate out from its center like spokes. Reflection from within the eye may give the appearance of a white pupil. MGS nearly always affects only one eye. Vision in the affected eye may be severely impaired or may worsen. There is an increased risk of retinal detachment.

     Eye Birth Defects Institute
myopia (mi-OH-pee-uh) or nearsightedness, is when the eyes are naturally focused up close, and adding special focusing efforts only bring the focus closer, so vision is always blurry for distant objects.

     Orbit and Eye Movement Institute
     Vision Development Institute
nasolacrimal duct obstruction (NLD). A fairly common condition in which the tear drainage from the eye into the nose – the nasolacrimal duct – is closed off. When a blockage occurs in the NLD, tears build up on the surface of the eye, preventing bacteria or debris from clearing. This may cause infections or discharge.

     Orbit and Eye Movement Institute
nearsightedness. See myopia.

ophthalmologist (ahf-thal-MAH-loh-jist). Physician (MD) specializing in diagnosis and treatment of refractive, medical and surgical problems related to eye diseases and disorders.

optic nerve. The nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex. The optic nerve in the brain is about one-and-a-half inches in length, and contains approximately 1.2 million nerve fibers.

     Eye Birth Defects Institute
optic nerve hypoplasia (ONH). A disease of the hypothalamus in the base of the brain. ONH is the under-development or absence of the optic nerve combined with possible brain and endocrine abnormalities. It is also known as Septo-Optic Dysplasia or DeMorsier's Syndrome. Now at epidemic proportions, ONH is the single leading cause of blindness and visual impairment in young children.

     Eye Birth Defects Institute
optometrist (ahp-TAHM-uh-trist). Doctor of optometry (OD) specializing in vision problems, treating vision conditions with spectacles, contact lenses, low vision aids and vision therapy, and prescribing medications for certain eye diseases.

orthoptics. Discipline dealing with the diagnosis and treatment of defective eye coordination, binocular vision, and functional amblyopia by non-medical and non-surgical methods, e.g., glasses, prisms, exercises.

patching. Covering an amblyopic patient's preferred eye, to improve vision in the other eye.

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

peters anomaly. In this rare congenital disorder, the cornea may be scarred, and cataracts and glaucoma can develop. Congenital clouding of the cornea, secondary to its maldevelopment, requires early transplantation for a child to see. This disease often involves physical delays in the child.

     Cornea Institute
     Vision Development Institute
posterior uveitis (u-v-ite'-us). An inflammation of the uvea, which may include areas of the eye such as the iris, ciliary body, and choroids. presbyopia. Occurs in adults, not children, is when the aging eye loses its ability to make special focusing efforts, resulting in the need for reading glasses to see up close.
pseudostrabismus. In pseudostrabismus, a child’s eyes appear to be crossed but are not true crossed eyes. The undeveloped facial features on the baby or child’s face often reveal the presence of pseudostrabismus.

     Orbit and Eye Movement Institute
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(Q-T)

pupil. The dark aperture or opening in the center of the iris which gets bigger or smaller, depending on the light coming in.

refraction. Test to determine an eye's refractive error and the best corrective lenses to be prescribed. Series of lenses in graded powers are presented to determine which provide sharpest, clearest vision.

     Orbit and Eye Movement Institute
     Vision Development Institute

refractive error. Refractive error, also referred to as refraction, or your child's eye prescription, is a measure of how sharply your child's eyes are naturally focused for far away when he or she is not making special focusing efforts. When there is no refractive error, the eyes are naturally focused for far distance, and special focusing efforts are only used to change the eyes' focus to closer objects. A large refractive error can cause blurry vision and may need glasses correction.

     Orbit and Eye Movement Institute
     Vision Development Institute
refractive surgery. Using sophisticate surgical techniques and state-of-the-art equipment, surgeons at the Cornea Institute reshape the corneal surface and remove the refractive error in the eye. Most refractive eye surgeries are performed on an outpatient basis, with most procedures lasting less than one hour in duration. The eye is usually numbed with eye drops prior to surgery. Recovery times vary depending on the surgery, but can last anywhere from a couple of days to a few months.

     Cornea Institute
retina (RET-ih-nuh). The retina, the inner layer and light sensing structure of the eye, contains a million rods and 7 million cones, which handle vision in low light and color, respectively.

     Retina Institute
retinal detachment. Separation of the 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.

     Retina Institute
retinitis pigmentosa. Usually inherited condition characterized by progressive degeneration of the retina, resulting in night blindness and decreased peripheral vision.

     Retina Institute
retinoblastoma (reh-tin-oh-blast-oma) (Rb). A malignant cancer of early childhood that arises from immature retinal cells in one or both eyes.

     Retina Institute
retinopathy of prematurity (ROP). The second leading cause of blindness in infants. It results from premature birth, which interrupts the normal development of blood vessels in the retina, the light sensitive part of the eye essential for vision. Abnormal blood vessels can begin to grow the wrong direction and lead to lifelong blindness.

     Retina Institute
retinoscope (RET-in-oh-skohp). Device for measuring an eye's refractive error with no response required from the patient. Light is projected into the eye, and the movements of the light reflection from the eye are neutralized (eliminated) with lenses.

rod. Light-sensitive, specialized retinal receptor cell that works at low light levels (night vision). A normal retina contains 150 million rods.

     Retina Institute
Septo-Optic Dysplasia. See Optic Nerve Hypoplasia.

strabismus (struh-BIZ-mus). Misalignment of the eyes, which makes it impossible for the brain to use the information from the two eyes together normally.

     Orbit and Eye Movement Institute
     Vision Development Institute
traumatic cataract. Injury to the lens causing the lens to become opaque.
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(U-Z)

vitreous (VlT-ree-us) body. A transparent jelly-like substance, which provides a cushioned support for the rest of the eye and a clear unobstructed path for light to travel to the retina. The vitreous humor, the clear gel in the vitreous body, makes up about 80% of the eye's total volume.

vitreous detachment. Separation of vitreous gel from retinal surface. Usually innocuous, but can cause retinal tears, which may lead to retinal detachment. Frequently occurs with aging as the vitreous liquifies, or in some disease states, e.g. diabetes and high myopia.

     Retina Institute
vitreous hemorrhage. Blood in the vitreous caused by bleeding from the iris, retinal vessels, underlying choroids and many other causes that may initiate bleeding in the eye.
vitreous traction. The vitreous is the clear gel in the eye and when we are born is adherent to the surface of the retina. As we get older (typically after the age of 20), the vitreous can separate from the retina. As it separates, it can "tickle" the retina and cause it to think that it is seeing lights (similar to what happens when you hit your funny bone). Once the vitreous separates cleanly, the flashes stop. In those cases where the vitreous is very adherent, it can't release and instead tears the retina at that spot, creating a hole that can lead to a retinal detachment.
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