Eyecare Glossary

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Accommodation

The eye's ability to adjust its focus from distant to near objects. This process is achieved by the lens changing its shape.

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Acuity

The clearness of eyesight; the keenness of the visual powers. AKA: Visual Acuity.

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Age-Related Macular Degeneration (ARMD, AMD or ARM)

A major cause of central vision loss which, in about 70% of the cases, is associated with aging and the breakdown of the retinal structures at the macula.

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Albinism

Congenital deficiency or absence of pigment (color) in the skin, hair, choroid, retina and iris.

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Amaurosis

Blindness.

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Amblyopia

Sometimes referred to as lazy eye, a condition of diminished visual acuity in the absence of any detectable anatomic or physiologic cause.

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American National Standards Institute (ANSI) Z87.1

The American National Standards Institute's Practice for Occupational and Educational Eye and Face Protection; eyewear that meets this standard is considered safer than eyewear that does not.

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Ametropia

Defective vision that is correctable by eyeglasses or contact lenses.

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Aniseikonia

A condition in which the image sizes in each eye are different, leading to difficulties in achieving single vision. Symptoms of aniseikonia are headaches and dizziness.

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Anisocoria

Different-sized pupils in each eye.

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Anisometropia

Greek meaning "not the same correction," anisometropia is when there is a significant difference in correction between the two eyes. This may cause eye strain and double vision (diplopia).

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Anterior Chamber

The space in front of the iris and behind the cornea.

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Antimetropia

One eye nearsighted; the other farsighted.

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Anti-Reflective Coating

Anti-reflective coatings reduce glare and enhance your appearance by removing distracting reflections.

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Aphakic

Condition of the eye with crystalline lens removed. Also refers to post-cataract patients who have had cataract surgery.

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Aqueous Humor

Also known as aqueous fluid: clear, watery fluid that flows between and nourishes the lens and the cornea.

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Arteriosclerosis

A chronic disease of the arteries characterized by the thickening or hardening of the arterial walls impairing blood circulation.

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Asthenopia

A group of symptoms generally referred to as "eye-strain." Included are: headaches, tearing, "tired eyes," itching, burning and blurred vision.

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Astigmatism

A condition that occurs when the front surface of the eye (the cornea) is slightly irregular in shape. This irregular shape prevents light from focusing properly on the back of the eye (the retina). As a result, vision may be blurred at all distances.

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Bifocal Lens

Lens with two focal lengths, one for distance and one for near. Usually the distance correction is on top and the correction for near is on the bottom.

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Blended Lens

While traditional multifocal lenses have a line in the middle of the lens, blended lenses (progressive lenses) are line-free. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance), moving invisibly from the top to the bottom of the lens.

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Blind Spot

(1) A small area of the retina where the optic nerve enters the eye; occurs normally in all eyes. (2) Any gap in the visual field corresponding to an area of the retina where no visual cells are present.

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Cataract

A cataract is a clouding of part or all of the lens inside the eye, resulting in blurred or distorted vision.

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Cataract Lens

Eyeglass lens used following cataract removal. Cataract lenses were once widely used for post-cataract patients; however, IOL (interocular) lenses are now the most commonly used replacement for the removal of the crystalline lens, eliminating the necessity for cataract lenses.

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Cathode Ray Tube (CRT)

The monitor or display screen of a computer. Special computer eyeglasses are available to increase or enhance vision while viewing computer screens.

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Choroid

The layer in the eye filled with blood vessels that nourishes the retina.

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Chromatic

Of or pertaining to color.

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Ciliary Muscle

The eye's focusing muscle that allows the crystalline lens to perform its function of accommodation.

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Coloboma

A defect of the iris caused by a failure of the eyeball to fuse properly during fetal development. These are developmental anomalies and do not worsen as the child grows older.

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Color Blindness

Also known as color deficiency, the inability to recognize colors.

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Computer Vision Syndrome (CVS)

The variety of eye and vision-related problems associated with prolonged computer use. CVS is characterized by eyestrain, blurred vision, headaches and dry or irritated eyes.

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Conjunctiva

The thin, moist tissue that lines the inner surfaces of the eyelids and the outer surface of the sclera (the outer layer of the eyeball).

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Conjunctivitis

Inflammation of the conjunctiva, often referred to as "pink eye."

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Contact Lens

A thin, bowl shaped lens worn on the surface of the eye.

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Contact Lens Drops

Eye drops for contact lens wearers; regular eye drops can discolor contact lenses.

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Contrast Sensitivity

The ability to perceive differences between an object and its background.

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Convergence

Simultaneous turning in of both eyes to keep objects in sight as they approach the eyes.

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Cornea

Serving to transmit light to the eye, the cornea is a transparent tissue that covers the front surface of the eye.

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Corneal Abrasion

A cut or scratch on the cornea

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Corneal Implants

Devices (such as rings or contacts) placed in the eye, usually to correct vision.

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Corneal Ring

A type of vision correction surgery where a doctor inserts a tiny plastic ring into the cornea (which lets light into the eye), reshaping the cornea and helping it to focus light better onto the retina to improve vision. The ring can be adjusted and even removed if desired.

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Corneal Topography

Mapping or examination of the cornea. The information gathered is useful to evaluate and correct many eye conditions.

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Corneal Ulcer

A wound in the outer layer of the cornea caused by injury, dryness due to lack of tear production or infection.

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Crossed Eyes

A misalignment of the eyes where one or both eyes point inward, toward the nose.

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Crystalline Lens

The crystalline lens is the lens of the eye, serving to focus light on the retina, and changing its shape allows one to focus at near or far distance.

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Dacryostenosis

A blocked tear duct, which is characterized by a lot of tearing.

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Daily Wear Contact Lens

Soft contact lenses worn every day for six months up to a couple of years, requiring daily cleaning and disinfecting, as well as a periodic enzymatic soak (usually once a week).

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Depth Perception

The ability to judge the distance and/or spatial relationship of objects of varying distances.

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Diabetes

A chronic, metabolic disorder where a lack of insulin secretion and /or increased cellular resistance to insulin results in elevated blood levels of glucose. Complications due to diabetes can include damage to the eyes, kidneys, nervous system and vascular system.

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Diabetic Retinopathy

A complication of diabetes that is triggered by damage to the blood vessels of the eye.

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Dilate

A process by which the pupill is temporarily enlarged with special eye drops. This allows an eye doctor to see more of the retina and look for signs of diabetic retinopathy and other eye diseases or health concerns. After the exam, close-up vision may remain blurred for several hours.

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Diopter

A diopter is a unit of measure for expressing the magnifying power of a lens or lens system. A one diopter lens has a focal distance of one meter. A two diopter lens has a focal distance of one-half meter.

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Diplopia

Also known as double vision, a visual disorder due to unequal action of the eye muscles causing two images of a single object to be seen.

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Disposable Contact Lens

Contact lenses that are thrown away after a short period of time. Usage of disposable contact lenses ranges from one day to two weeks, while frequent replacement lenses are discarded monthly or quarterly.

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Divergence

Simultaneous turning out of both eyes to keep sight of an object as it moves farther from the eyes.

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Dominant Eye

The eye that "leads" its mate during eye movements.

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Double Bifocal Lens

An occupational lens with a bifocal on the bottom and the top of the lens.

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Dye

A color that is absorbed into a plastic lens.

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Edge Coating

Lens edges can be painted or color-treated to disguise thick edges of lenses or to coordinate with frame color for cosmetic reasons.

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Edge Polish

Both glass and plastic lens edges can be polished to a high luster resulting in clear and shiny lens edges. This option is often chosen with rimless frames to disguise the edges of the lenses, especially if they are thicker.

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Endothelium

The cornea's inner layer of cells.

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Enzymatic Cleaner

Used for contact lenses, a cleaner that removes protein deposits and other debris. It's recommended for use either daily, weekly, or monthly. Some enzymatic cleaners are a small tablet dropped into a solution along with the lens; others come in liquid form.

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Epithelium

The cornea's outer layer of cells.

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Esotropia

The turning inward of the eye.

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Executive Lens

Bifocal or trifocal that extends across the full width of the lens. Executive lenses offer the advantage of wide field of vision in reading area.

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Exotropia

The turning outward of the eye

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Extended Wear Contact Lens

Contact lenses that are worn without removal for up to seven days.

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Eye Care Doctor

Optometrists (O.D.s) and ophthalmologists (M.D.s).

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Faceted Lens

Polished, beveled edge lens put in a rimless frame.

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Farsightedness

Also known as Hyperopia, the inability to see objects up close. It is the result of an eyeball that is too short or whose outside surface (the cornea) is too flat. The exact cause is not known, although farsightedness may be inherited.

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Floaters

Cells and fragments of debris in the eye that pass across your field of vision.

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Focal Length

Distance from the optical center of the back surface of the eye to the principal focus of the lens.

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Focus

The point at which light rays through a lens form an image.

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Fovea

A depression in the retina that contains only cones (not rods), and that provides acute eyesight.

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Frequent Replacement Contact Lens

Any contact lens that is thrown away after a moderately short period of time, anywhere from one day to two weeks (disposables) to monthly or quarterly (frequent replacement).

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Fundus

The interior lining of the eyeball, including the retina, optic disc, and macula. This portion of the inner eye can be seen during an eye exam by looking through the pupil.

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Ghost Image

Often referred to when describing the benefits of anti-reflective coatings, the internal reflections from the lens surfaces. Ghost images are mostly experienced at night.

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Glass Lens

The most scratch-resistant lens material. Heavier than plastic lenses, glass comes in a wide selection of lens styles and can be ordered with absorptive and photochromic tints.

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Glaucoma

An eye disease in which the passages that allow fluid in the eye to drain become clogged or blocked, or there is too much fluid produced inside of the eye. Increased pressure inside the eye then damages the optic nerve and causes vision loss.

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Gonioscopy

Use of a special contact lens to look at the eye's aqueous drainage area. This can be thought of as looking at the drain of the eye to see if it's plugged up.

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Gradient Tinting

Usually applied for cosmetic purposes, gradient tinting is darker at the top of the lens than in the middle and lightest at the bottom.

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Graves' Ophthalmopathy

Thyroid-related, autoimmune eye disorder usually associated with Graves' disease; symptoms include eyelid retraction, bulging eyes, light sensitivity, discomfort, double vision and vision loss.

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Gross Visual Fields

A brief 5 to10 minute test in which the doctor examines your peripheral (side) vision. The test can be conducted using specialized equipment or simply by having you follow a focal point.

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Hard Contact Lens

Small, hard contact lenses. Compared with soft and rigid lenses, hard contact lenses are less healthy to wear long-term, since the material doesn't allow oxygen to reach the surface of the eye.

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High Blood Pressure (Hypertension)

Abnormally high arterial blood pressure.

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High Index Lens

A thinner and lighter lens in either glass or plastic, chosen for lightweight comfort and attractiveness.

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Hyperopia

Also know as farsightedness, the inability to see objects up close. It is the result of an eyeball that is too short or whose outside surface (the cornea) is too flat. The exact cause is not known, although farsightedness may be inherited.

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Hypotropia

A turning downward of one eye.

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Intermediate Zone

Refers to the middle zone of sight. Considered to be an arm's length, the top trifocal segment in a multifocal lens corrects vision for this distance.

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Interpupillary Distance

Commonly referred to as PD, the distance between your pupils.

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Intraocular Lens (IOL)

A lens implanted during cataract surgery to replace a damaged lens.

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Intraocular Pressure (IOP)

Pressure inside the eye.

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Iris

The colored ring of tissue suspended behind the cornea and immediately in front of the lens. It regulates the amount of light entering the eye by adjusting the size of the pupil.

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Jaeger Test

Measurement of visual acuity at the reading distance.

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Keratitis

Inflammation of the cornea. Keratitis may be deep, when the infection causing it is carried in the blood or spreads to the cornea from other parts of the eye, or superficial, caused by bacterial or viral infection or by allergic reaction. Burns of the cornea, such as those produced by chemicals or ultraviolet rays, also give rise to a form of keratitis.

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Keratoconus

A degenerative corneal disease in which the center of the cornea thins and the cornea becomes conical, rather than spherical, in shape.

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Keratometry

Assessing the eye's shape to check for astigmatism.

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Lacrimal Gland

The small, almond-shaped structure that produces tears, it is located just above the outer corner of the eye.

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Lateral Rectus Muscle

Muscle that moves the eye away from the nose.

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Laser In-Situ Keratomileusis (LASIK)

A medical procedure in which a doctor uses an excimer laser to reshape the cornea under a flap of corneal tissue.

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Lazy Eye

Also know as Amblyopia, a condition of diminished visual acuity in the absence of any detectable anatomic or physiologic cause.

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Legal Blindness

In the United States, (1) visual acuity of 20/200 or worse in the better eye with corrective lenses (20/200 means that a person must be at 20 feet from an eye chart to see what a person with normal vision can see at 200 feet), or (2) visual field restricted to 20 degrees diameter or less (tunnel vision) in the better eye.

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Lens

(1)The transparent structure in the front of the eye. With outward curves on both sides, the lens helps focus light on the retina. (2)A piece of glass or other transparent material having two polished opposite surfaces, at least one of which is curved.

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Lens-Aphakic

A spectacle lens worn after cataract surgery when an intra-ocular lens implant is not put into the eye after the cataract is removed.

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Lensometer, vertometer

Instrument used to measure the power of a spectacle lens.

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Lenticular Lens

Used primarily for post-cataract lenses, a lenticular lens is one in which the power is in the center of the lens but the edge is a portion of plain glass, so it is easily mounted in a frame. Lenticular lenses are designed to reduce the weight and thickness.

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Limbus

Circular zone where the cornea joins the sclera (white of the eye).

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Low Power Aspheric Lens

This term applies to all aspheric lenses not specifically designed for post-cataract use.

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Low Vision

Also called partial sight, low vision is sight that cannot be satisfactorily corrected with glasses, contacts, or surgery. Low vision usually results from an eye disease such as glaucoma or macular degeneration.

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Macula

The small, sensitive area of the central retina, providing vision for fine work and reading.

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Magnify

An apparent increase in the size of an object.

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M.D.

A doctor of medicine.

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Medial Rectus Muscle

Muscle that moves the eye toward the nose.

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Microcornea

Abnormally small cornea.

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Microkeratome

A small instrument used to cut the cornea.

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Migraine

Type of headache that usually occurs on one side of the head and is accompanied by visual disturbances, such as sparkles and spots before the eyes.

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Mires Distortion

Mires Distortion is a measurement process that figures one arm of an opthalmometer whose images are reflected on the cornea. The measurement variation determines the amount of corneal astigmatism. This process is done in conjunction with Keratoconus.

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Mirrored Lens

Also know as Ski Type Coating, Mirrored Coatings protect eyes from glare and from the sun's infrared rays. The lenses come in a variety of colors to enhance your visual performance.

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Mono-Centric Lens

Bifocal with both distance and reading segment sharing a common optical center.

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Monocular

Pertaining to one eye.

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Multifocal Lens

Eyeglass lens incorporating two or more different powers, usually three (trifocal).

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Myopia

Also known as nearsightedness, is the inability to see clearly at a distance. It's the result of an eyeball that is too long or whose outside surface (the cornea) is too curved. Nearsightedness can be inherited or caused by the stress of concentrating for long periods on close work.

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Near Point

Denotes distance used in conventional reading, generally considered 14 inches.

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Nearsightedness

Nearsightedness (Myopia) is the inability to see clearly at a distance. It's the result of an eyeball that is too long or whose outside surface (the cornea) is too curved. Nearsightedness can be inherited or caused by the stress of concentrating for long periods on close work.

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No-Line Lens

Also known as progressive lenses or blended lenses , multifocal (bifocal and trifocal) lenses that have no line in the middle of the lens. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance), moving invisibly from the top to the bottom of the lens. This option is available for glass and plastic lenses.

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Nystagmus

Involuntary rapid and repetitive movement of the eyes.

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Occupational Lens

Any lens prescribed primarily for a specific visual task at work, or for participation in a hobby, sport, or other leisure activity. Usually applied to special design multifocals, but any lens can serve as an occupational lens.

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Ocular

Pertaining to or depending on the eye; received by actual sight.

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Ocular Hypertension

A condition where the intraocular pressure of the eye is above normal. Ocular hypertension can lead to glaucoma.

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OD

Latin abbreviation for right eye; abbreviation for Doctor of Optometry.

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Ophthalmic

That which pertains to the eye.

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Ophthalmologist

A doctor of medicine (M.D.) who is both a medical doctor and a surgeon. The ophthalmologist is licensed to perform surgery, conduct eye exams, treat disease, and prescribe medication, as well as prescribe corrective lenses (glasses or contacts).

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Ophthalmology

The medical specialty encompassing the anatomy, functions, diseases and treatment of the eye.

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Ophthalmoscopy

An exam of the retina. The doctor looks through a device with a special magnifying lens that provides a narrow view or a wide view of the retina.

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Optic Nerve

The bundle of more than a million nerve fibers that carry visual messages from the retina to the brain.

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Optometrist

A doctor of optometry (OD) who is licensed to examine eyes for the prescription and fitting of corrective lenses (glasses and contact lenses). An optometrist also specializes in the exam, diagnosis, treatment and management of diseases and disorders of the visual system, the eye and associated structures, as well as diagnosis of related systemic conditions.

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Optometry

The profession of examining, diagnosing, managing and treating eye diseases and defects of the visual system and associated structures.

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Orthokeratology

Fitting of hard contacts of differing curvature to achieve a change in the prescription, although temporary.

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Orthoptics

Also called Vision Therapy, the science of correcting defects in binocular vision resulting from defects in optic musculature or faulty visual habits.

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Overconvergence

A condition where the eyes come too far inward when focusing on a near object, resulting in blurring.

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Oversize Lens

Frames with lens sizes that will not cut out of conventional size lens blanks are considered oversized, generally when the size of the frame is 61mm or larger.

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Palpebral Fissure

The space between the upper and lower eyelids when the eyes are open.

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Palpebrum

Eyelid.

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Papilla

A small bump where the optic nerve exits the eye.

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Pathology

Structural and functional deviations from the normal that consitute disease or characterize a particular disease.

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Peripheral Vision

Side vision or what an eye can see to the side while looking straight ahead.

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Photochromic Lens

Photochromic lenses darken automatically when exposed to ultraviolet light, specifically sunlight, and lighten with reduced exposure to sunlight.

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Photokeratitis

Sunburn of the cornea caused by exposure to ultraviolet radiation. Symptoms of photokeratitis include discomfort, blurred vision, and light sensitivity. The temporary vision loss that can result is called "snow blindness."

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Photorefractive Keratectomy (PRK)

A surgical procedure in which the doctor uses an excimer laser to reshape the cornea to correct vision problems.

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Pilot Shape Lens

Initially used for aviators' goggles in World War II, one of the most popular lens shapes, featuring a gradual nasal flare towards the bottom of the lens.

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Pinguecula

A yellowish, thickened lesion on the conjunctiva.

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Plano Lens

A term to describe a lens without prescription. The term is most often applied to nonprescription sunglasses or contact lenses that are worn for cosmetic purposes only. Also, used to describe no curvature or flat lens.

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Plastic Gradient Dyes

Typically used for cosmetic reasons, plastic lenses with plastic gradient dyes are usually dark at the top and gradually become lighter toward the bottom of the lenses.

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Plastic Lens

Refers to non-glass lenses, which are impact resistant and lightweight. Plastic lenses are almost half the weight of glass in the same prescription.

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Polarized Lens

Available in glass and plastic, polarized lenses protect against reflected glare from water, snow or shiny surfaces.

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Polycarbonate Lens

More durable than regular plastic, polycarbonate lenses are very lightweight. They also have greater impact resistance than any other lens material, making it the lens of choice for sports eyewear, children or active lifestyles.

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Post Cataract Aspheric Lens

Early aspheric lenses were lenticular, full-field and used for high-plus post-cataract glasses. Use of these lenses has been virtually eliminated by the introduction of intraocular lenses (IOL).

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Post Cataract Surgery

After cataract surgery.

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Posterior Chamber

Filled with aqueous fluid, the space between the back of the iris and the front face of the vitreous.

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Presbyopia

Occurring in almost all people over age 45, the gradual loss of the eye's ability to change focus for seeing near objects. It happens because, with age, the lens inside the eye gradually loses its flexibility and focusing ability.

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Prescription Lens

Prescribed by an eye care practitioner, lenses that correct vision problems.

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Prism

A wedge shaped piece of glass or plastic having a base, apex and apical angle. A prism may help eyes work together as a team when eyes are not aligned.

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Progressive Lens

While traditional multifocal (bifocal and trifocal) lenses have a line in the middle of the lens, progressive lenses are line-free. The power gradually changes from distance correction to intermediate vision (at arm's length), to near vision (at reading distance), moving invisibly from the top to the bottom of the lens.

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Ptosis

Ptosis is a drooping of the upper eyelid. The lid may droop only slightly, or it may cover the pupil entirely. In some cases, ptosis can restrict and even block normal vision. It can be present in children, as well as adults, and is usually treated with surgery.

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Pupil

Often compared with the shutter of a camera, the pupil is the black, circular "hole" in the iris that regulates the amount of light entering the eye. The pupil appears black and the contents beyond it dark because of the absence of light inside the eye, similar to the way a dark room looks when viewed from a lighted one. By using a special instrument called an ophthalmoscope, eye doctors are able to examine the inside of the eye.

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Pupillary Distance (P.D.)

Also known as interpupillary distance, the distance from the center of one pupil to the center of the other.

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Pupillary Reflex

Automatic contraction of the pupil when exposed to light and automatic dilation when the light source is removed.

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Quadrifocal Lens

A lens with four different focusing areas, usually a trifocal with an added top bifocal segment. Also used in some occupational lens featuring trifocal in the bottom half of lens and bifocal at the top for seeing close when looking upwards.

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Radial Keratometry (RK)

Surgery to change the shape of the cornea to reduce nearsightedness. Not covered under VSP.

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Refraction

The portion of the exam that determines your prescription.

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Refractive Error

The inability of the eye to focus images properly on the retina, including myopia (nearsightedness), hyperopia (farsightedness) and astigmatism.

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Refractive Surgery

Surgery that corrects visual acuity, with the objective of reducing or eliminating the need for glasses and contacts. Refractive surgery includes radial keratotomy, PRK, LASIK, and corneal implants.

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Replacement Schedule

Refers to the frequency you discard and replace your contact lenses: every day, week or two weeks (disposable); or every month, two months or calendar quarter (frequent replacement).

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Retina

The retina is the light-sensitive layer of tissue that lines the back of the eyeball, sending visual impulses through the optic nerve to the brain.

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Retinal Detachment

A condition in which the retina separates from the inner wall of the eye.

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Retinal Pigment Epithelium

The pigment cell layer that nourishes the retinal cells. It is located just outside the retina and attached to the choroid.

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Retinitis Pigmentosa

The progressive loss of peripheral vision, usually beginning with night blindness.

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Retinoblastoma

A malignant cancerous tumor of the retina.

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RGP (Rigid Gas Permeable) Lens

The successor to hard contact lens, RGP contact lenses are made of breathable plastic that is custom-fit to the shape of the cornea.

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Rod

A photosensitive receptor in the retina that helps you to see in low light.

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Safety Lens

A lens designed to protect the eyes. True safety lenses are made only in safety labs to standards of 3.0mm thickness, mounted in a safety frame and tested by a lab.

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Sclera

The tough, white, outer layer (coat) of the eyeball. Along with the cornea, it protects the entire eyeball.

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Scratch-Resistant Coating

Scratch-Resistant Coating is added to increase your lens durability by protecting your lenses from everyday wear and tear.

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Sign

Sign of addition (+) represents plus or magnifying lenses. Sign of subtraction (-) represents minus or minifying lenses.

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Silicon Coating

A recent development in eyewear, silicon coating is applied over the top of anti-reflection coatings, leaving a smooth water-resistant surface that is easier to clean.

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Single Vision Lens

Lens with one power, as opposed to bifocals, trifocals, quadrifocals or multifocals.

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Ski Type Coating

Also know as Mirrored Lens Coating, Ski Type Coatings protect eyes from glare and from the sun's infrared rays. The lenses come in a variety of colors to enhance your visual performance.

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Slab-Off

Placing two different curvatures on the front surfaces of a pair of lenses to eliminate vertical imbalance at reading distance, enabling your eyes to work together more easily.

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Soft Contact Lens

Contact lenses made of gel-like plastic containing varying amounts of water.

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Solid Tints & Dyes

Chosen for cosmetic purposes or to reduce the amount of light coming through eyeglass lenses.

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Solution

Products used to clean, disinfect and store contact lenses.

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Strabismus

A condition of abnormal alignment of one eye in relation to the other. Esotropia and crossed eyes are types of strabismus.

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Stroma

The middle layer of the cornea; it consists of lamellae (collagen) and cells, and makes up most of the cornea.

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Stye

A blocked gland at the edge of the eyelid which has become infected by bacteria.

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Suspensory Ligament

Part of the eye that holds the lens in place.

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Tear Duct

Tiny opening in the eyelid through which tears drain into the nose.

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Tinting

Most non-glass lenses can be dyed to add color for cosmetic purposes or to reduce light transmission. Glass lenses must be made from colored glass or have color applied by vacuum coating.

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Titanium Frames

Titanium frames have high tensile strength and are very lightweight.

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Tonometry

A standard test used as part of an eye exam that determines the fluid pressure inside the eye.

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Toric Lens


Used to correct astigmatism, a lens containing a cylindrical (or out-of-round) surface. A toric surface is ground with two different curves at right angles to each other with the weaker of the two curves located on the cylinder's axis.

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Traumatic Cataract

Describes a type of cataract caused by injury.

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Trifocal Lens


A lens having three areas of viewing, each with its own focusing power. Usually, the upper power is used for distance vision, the lower power for close vision such as reading, and the middle area for "arms length" vision.

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Tumors (of the eye, brain, or near eye)

An abnormal growth of tissue.

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20/20 Vision

The 20 on the left indicates that the eye chart is 20 feet away. The 20 on the right means that from that distance, you can see what normal eyes see at 20 feet. In other words, you have normal vision. However, if your vision is 20/40, it means you must stand 20 feet away to see what normal eyes see from 40 feet. If your vision is 20/15 you can see from 20 feet what normal eyes see from at 15 feet - much better than normal vision.

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Ultraviolet (UV) Protection

Lens treatment applied to absorb the harmful portion of UV light found in sunlight.

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VDT

The abbreviation for Video Display Terminal, the monitor portion of a computer.

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Vision Analysis

An eye exam which can include:
Case History - Patient's past history, medications, general health, ocular symptoms, and family history.
Visual Acuities - At distance 20' or greater at near 16' or 40' centimeters.
External examination.
Pupillary Reflexes - checking to see if pupils are round and display equal reaction to light.
Versions - checking that the eyes work together in different fields of gaze.
Cover Test - At distance and near, checks binocularity.
Ophthalmoscopy - using an ophthalmoscope to view the retina, optic nerve, head and blood vessels.
Retinoscopy - using a retinoscope to determine the patient's refraction by objective means.
Refraction - determining the patient's refractive error by subjective means.
Binocular - measurements far and near, used to measure the ability of the eyes to work together.

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Vision Therapy

A set of exercises to correct minor visual problems associated with sensory and/or muscular deficiencies of the visual system. Examples: cross-eyed, wandering eye.

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Visual Acuity

The ability to distinguish details and shapes of objects at varying distances.

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Visual Field

Area of vision the eye can see while its attention is directed straight ahead.

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Visual Fields Test

A five to ten minute test in which the doctor examines your peripheral vision. The test is conducted using specialized equipment or by having you follow a focal point.

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Vitrectomy

The surgical removal of the vitreous humor, which is the clear, jelly-like substance that fills the center of the eye in front of the retina.

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Vitreous Body

The transparent, colorless mass of gel that lies behind the lens and in front of the retina.

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Wear Schedule

Refers to how long you wear your contact lenses: either daily wear (lenses are removed each night) or extended wear (lenses can be slept in).

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Zonule

The part of the eye that holds the lens in place.

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