Glossary

Normal visual acuity; upper number is the standard distance between the tested eye and the eye chart, and the lower number is the distance at which the tested eye can see the same standard-sized letters as a normal eye at 20 feet.

Eye rotation away from the midline.

Blurred or distorted image quality resulting from the physical properties of an optical device (ie, lens)

Acanthamoeba Keratitis is a rare but serious infection of the eye that can result in permanent visual impairment or blindness. This infection is caused by a microscopic, freeliving ameba (single-celled living organism) called Acanthamoeba. Acanthamoeba causes Acanthamoeba Keratitis when it infects the transparent outer covering of the eye called the cornea. Acanthamoeba are very common in nature and can be found in bodies of water (for example, lakes and oceans), soil, and air. Anyone can get acanthamoeba keratitis, but it's most common in people who wear soft contact lenses. You have a greater risk of this condition if you: Swim or shower with contact lenses on or clean your contact lenses with tap water instead of disinfectant solution.

The eye’s increase in optical power in order to maintain image clarity as objects are moved closer

Additional lens power associated with your multifocal, bifocal, or progressive lens prescription needed to make it easier for you to read.

Eye rotation toward the midline

Refers to the extent to which a patient follows a doctor’s treatment regimen without close supervision

Additive treatment or medication that enhances the benefit of another treatment or medication

Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision; the most common cause of decreased vision after 50

Lack of tear production

Lack of pigment in the eyes, hair, and skin, which is usually associated with decreased visual acuity

An antigen that creates an allergic or hypersensitivity response

Inflammation of the conjunctiva from hypersensitivity to allergens

Argon laser trabeculoplasty; surgical procedure that uses a laser to create small burns in the trabecular meshwork to lower intraocular pressure

Also called lazy eye. Decreased vision in one eye that leads to the use of the other eye as the dominant eye. A problem most commonly associated with children.

Rise in intraocular pressure due to aqueous fluid behind the iris being unable to pass through the pupil; patients with anatomically narrow angles are predisposed to this condition

Loss of vision, particularly to part of the visual field

Space between the iris and innermost corneal surface that is filled with fluid

A lens treatment for your glasses that helps to reduce distracting glare and eye fatigue by reducing the amount of light reflecting off the lens surface and making the lenses appear clearer. Your eyes will also be more visible behind the lenses

Absence of the eye’s crystalline lens, such as after cataract extraction

Instrument that flattens the cornea to measure intraocular pressure

Clear fluid that fills the space in the eye between the cornea and the lens; maintains intraocular pressure and provides nourishment to the cornea, iris, and lens

Passage of aqueous fluid through the anterior chamber angle structures

Eyedrops with similar consistency to natural tears to alleviate Dry Eye symptoms

Refractive error that prevents the eye from focusing sharply, usually resulting from an abnormally shaped corneal surface; correctable by eyeglasses, contact lenses, or refractive surgery

The axis indicates the angle (in degrees) between the two meridians of an astigmatic eye. The axis is defined with a number from 1 to 180.

Inflammation of the conjunctiva caused by a bacterial infection; usually contagious.

Inflammation of the conjunctiva caused by a bacterial infection; usually contagious

Innermost layer of the choroid, directly under the retina; damage to the basal lamina is responsible for many bleeding disorders of the macula area

A number usually between 8 and 10 that conforms to the shape of your eye with your contact lens prescription.

Condition in which muscles of the brows, eyelids, and mouth are paralyzed by damage to the 7th cranial nerve; may cause affected eyelids to remain open, resulting in corneal drying

Twice daily

Eyeglasses that incorporate lenses of 2 different powers; allows for both near and far distance sight without changing eyewear

Referring to or affecting both eyes

Flap of tissue created to cover a sclero-corneal drainage channel during glaucoma surgery; enhances fluid outflow from the eye

Inflammation of the eyelids; may be caused by infection or allergy

Inflammation of the conjunctiva

Sudden, involuntary spasm causing uncontrolled blinking and squeezing of the eyelid

Non-seeing area within every visual field; caused by absence of photoreceptors where the optic nerve enters the eye

Inability to see

Periodic contraction of the eye muscles approximately every 5 seconds, causing the eyelid to close over the eye, spreading tears over the eye and limiting light entering the eye

Blue light blocking lenses offered at LensCrafters®. They offer two different options: one called Blue IQ™ lenses, which block about 52 percent of blue light, and another called Blue IQ Clear™ lenses, which block about 20 percent of blue light.

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Blue light is all around us. It comes primarily from the sun and it's what makes the sky look blue. Artificial blue light is also emitted by devices like computers, smartphones, flat-screen televisions LED lights, and energy-efficient light bulbs.

Incision to remove part of the lens capsule.

Incision to remove part of of the lens capsule

A cataract is a clouding of the crystalline lens of the eye that makes it hard for light to pass through and be focused properly. In a normal eye, the crystalline lens is almost transparent, however injury, age or disease can cause the lens to eventually loose its clarity. When the lens becomes 'opaque', it is called a cataract. Treatable by surgery.

First branch of the ophthalmic artery; provides nutrients to the inner two-thirds of the retina.

Collects retinal venous blood drainage and exits through the optic nerve.

Inflamed bump in the eyelid's meibomian gland.

Swelling of the conjunctiva.

Vascular Layer of the eye between the retina and sclera, providing nutrients to the outer layers of the retina.

Inflammation of the choroid.

Corneal/conjunctival dryness due to deficient tear production; keratoconjunctivitis sicca, Dry Eye syndrome.

Tissue in the eye that is involved in lens accommodation, intraocular pressure control, and producing the aqueous humor.

Collagen Cross-linking is procedure done to slow down the progression of Keratoconus. This treatment uses a combination of specially formulated eye drops and precisely applied UV light to create new bonds between the collagen fibers in your cornea. This strengthens and firms a cornea that has been weakened and thinned by keratoconus.

A lack of ability to distinguish certain colors. Commonly called "color blindness", the most common form of color deficiency is the inability to distinguish shades of red and green.

Refers to a patient following a doctor's treatment regimen.

High intraocular pressure, hazy corneas, and large eyes in children from newborn to 6 months old; developmental abnormalities prevent normal fluid drainage from the eye; requires surgical intervention.

Mucous membrane covering the outer surface of the eyeball (except the cornea) and inside surface of the eyelids.

Redness of the conjunctiva; associated with all types of conjunctivitis.

Pocket of conjunctiva between the upper eyelid and eyeball and lower eyelid and eyeball that permits the eyeball to rotate freely.

An eye condition caused by the inflammation of the conjunctiva, or clear membrane covering the white part of the eye and lining of the eyelids. The eyes will often appear swollen and red while also feeling gritty. It can be bacterial, viral, or allergic and could be contagious. Call or see your doctor to treat conjunctivitis.

Small disc worn on the cornea or sclera, providing visual correction of refractive errors.

Moving both eyes towards each other to maintain single binocular vision of an approaching object.

Displacement of the pupil from its normal position.

Transparent front of the eye covering the iris, pupil, and anterior chamber; provides the bulk of the eye's optical power.

Scraped area of the cornea accompanied by superficial tissue loss.

Central 3-5 mm where the cornea has the greatest curvature.

Hazy and swollen cornea.

Loss of the outer layer of the cornea because it fails to adhere to the Bowman's membrane.

Corneal hydrops is a complication of advanced keratoconus and is characterized by sudden onset of severe corneal opacification because of edema. The edema occurs from a spontaneous break in Descemet's membrane (one of the 5 layers of the cornea) because of the weakened cornea, leading to a sudden and painful decrease in visual acuity.

Use of dye such as fluorescein to reveal corneal epithelial defects.

Replacement of damaged or diseased cornea with donor corneal tissue.

Steroid used to treat inflammatory and allergic diseases.

The eye's natural lens located directly behind the iris. It has the ability to change shape to focus light rays onto the retina.

Optic cup; depression in the center of the optic disc that normally occupies less than one-third of the dis diameter.

Evaluates the progression of glaucoma by indicating the percentage of the disc occupied by the optic cup.

Abnormal enlargement of the optic cup, usually due to a long-term increase in intraocular pressure.

Use of a lens that produces different refractive power in each meridian; used to correct astigmatism.

Retinal swelling and cyst formation ion the macular area, can result in temporary or permanent decrease in vision.

Inflammation of the tear sac, often associated with poor tear drainage.

Awareness of relative spatial location of objects; perception of nearness and farness.

The leaking of retinal blood vessels into the macula in patients with diabetes, causing the macula to swell, which can temporarily or permanently decrease central vision.

Progressive retinal changes that accompany diabetes mellitus; this can progress from background retinopathy to proliferative retinopathy, which includes abnormal new blood vessels and fibrous tissue development.

The distance from one side of the lens to the other, usually around 13 to 15 millimeters that is associated with the size of your contact lenses.

Widening of the pupil.

Perception of two images from one object; double vision

Optic disc; ocular end of optic nerve

An eye condition that presents itself as itching, burning, and irritation of the eyes, is often called "dry eye syndrome". It is one of the most common problems treated by eye care professionals. It is usually caused by the breakdown (or deficiency) in the tears that lubricate the eyes. As we age, our bodies produce less oil to seal the eyes' watery layer. Hot, arid climates, air conditioning, certain medicines and irritants such as cigarette smoke can all increase dryness of the eye. Your eye care professional might prescribe "artificial tears" or other eye drops to help alleviate the problem.

Distorted shape of pupil.

Vertical skin fold at each side of the nose; hides the caruncle; present in infants before nose bridge is developed.

Overflow of tears down the face caused by poor tear drainage, excessive tearing, or outward turning of the lower eyelid.

Abnormal skin redness caused by capillary congestion under the skin.

Eye misalignment in which one eye turns inward while the other stays fixed straight ahead.

Procedure that removes the contents of the eyeball, leaving behind the sclera shell and, sometimes, the cornea; usually for reducing pain in a blind eye.

Eye misalignment in which one eye turns outward while the other stays fixed straight ahead.

Corneal irritation or inflammation caused by corneal drying due to incomplete closure of the eyelid.

Diseases that affect the cornea, sclera, conjunctiva, or eyelids.

Sense organ for sight.

One of the stiff hairs at the margin on the eyelid.

Structure covering the front of the eye that protects it, limits the light entering in, and distributes the tear film over the corneal structure.

The sclera and the cornea.

Refractive error that allows the eye to see clearly at a distance, but close-up images are blurred; hyperopia

Short-pulse laser that is used to create corneal flaps in refractive surgery.

Flashes are a visual sensation that can look like a camera flash going off or a lightning streak in your vision. Flashes occur because the vitreous or "jelly" is tugging on the retina. If the vitreous tugs too hard, it may cause a vision threatening event called a retinal tear or detachment. If you notice a sudden increase in the number of flashes you see, call your eye care professional.

A generalized term used to describe small specks moving subtly but noticeably in your field of vision. A floater or a spot is likely a tiny clump of gel or cells in the vitreous — the clear, jelly-like fluid inside your eye. Aging, eye injury and breakdown of the vitreous are the main causes of floaters and spots. If you notice a sudden increase in the number you see, call your eye care professional.

Colored dye that illuminates; used on the cornea to identify damage.

Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.

Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.

Tiny elevations on the undersurface of the eyelids; associated with viral conjunctival inflammation.

The feeling of something in the eye; can be caused by an actual foreign body in the eye or by various damage or conditions.

A tiny spot in the center of the retina that contains only cone cells. This area is responsible for our sharpness of vision.

Interior posterior surface of the eyeball which includes the retina, optic disc, macula, and posterior pole.

Degenerative change that produces a white ring-shaped deposit of fat near the peripheral edge of the cornea; typically in patients over 60.

Clinical test that determines the extent to which a bright light shined in the eye changes visual acuity; evaluates the degree of visual impairment caused by a cataract.

A common cause of preventable vision loss that is due to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Treatable by prescription drugs or surgery.

The eyeball; a sensory organ that uses light to transmit visual information to the brain; 3 major layers in the globe include corneo-sclero, uvea, and retina.

Large mucous glands in the conjunctiva that secrete mucin, a component of precorneal tear film; can be damaged in Dry Eye sydrome.

Test that examines the anterior chamber angle structures through a special lens with a slit lamp.

Surgical procedure that is often used to treat congenital glaucoma; it consists of an incision in the trabecular meshwork.

Symptoms of the eye that may result with excessive thyroid-related concentration, including eyelid retraction, eyelid lag, corneal drying, and optic nerve inflammation.

Hazy ring seen around lights; can be a sign of a refractive error or optical defect such as cataract.

Eye infection caused by the herpes simplex virus. Results in inflammation and ulcers.

Having a different color iris in each eye.

A dense lens material that results in thinner, lightweight lenses than standard plastic. Index refers to index refraction which is the speed that light travels through the lens. Higher index lenses are available from 1.56 to 1.74 (the higher the number, the thinner the lens). They benefit people with stronger prescription eyeglasses.

Chemical that creates an allergic or inflammatory response.

Acute infection of oil glands of the eyelid; externally, also known as a stye; internally (in the meibomian glands), also known as a chalazion, if chronic.

Clinical sign; increased blood flow; usually refers to eye redness due to increased blood flow to the conjunctival blood vessels.

A condition where they eye is too short for its optical power causing distant objects to be seen clearly, yet objects close up are seen less clearly. Also commonly referred to as "farsighted."

Functional defect in which one eye deviates upward while the other remains straight and fixates normally.

Clinical sign; blood in the anterior chamber, often following blunt trauma to the eyeball.

Functional defect in which one eye deviates downward while the other remains straight and fixates normally.

Lens that may be surgically implanted to replace the eye's natural lens.

The pressure of fluid within the eye; elevated IOP is a treatable risk factor for glaucoma.

Removal of a portion of iris tissue.

Pigmented tissue behind the cornea that gives the eye its color and allows light to enter the eye by controlling the size of the pupillary opening; part of the uveal (middle) layer of the eye.

Inflammation of the iris, causing pain, tearing, blurring, small pupil, and red congested eye.

Equal vision in both eyes.

Surgical removal of corneal tissue.

Corneal inflammation; can be caused by a variety of infections, injuries, and unknown causes.

Corneal and conjunctival dryness due to deficient tear production; Dry Eye syndrome.

– Keratoconus is a condition that causes progressive weakening, thinning and cone-like bulging of the cornea. This irregularity in the shape of the cornea causes light rays hitting the cornea to become out of focus and results in blurry and distorted vision that cannot be corrected by wearing glasses. Distorted vision from Keratoconus can be corrected by special gas permeable contact lenses. Corneal damage from Keratoconus is not reversible however its progression can be slowed down and even halted completely by a procedure called Collagen Cross-linking. In severe cases of keratoconus, transplantation of the cornea may be necessary.

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Corneal melt; superficial corneal layers that "melt" away; often associated with severe inflammation, Dry Eye, or rheumatoid arthritis.

Surgical procedure on the cornea that usually refers to a corneal graft (replacing damaged corneal tissue with donor tissue).

Any incision into the cornea (surgical procedure).

Almond-shaped gland located above the eyeball in the upper outer region that produces tears.

Tear production; crying.

Acronym for Light Amplification by Stimulated Emission of Radiation; a high-energy light source that can cut, burn, or dissolve tissues for clinical procedures; used in many eye care procedures such as refractive surgery, treatment of diabetic retinopathy and macular degeneration, and removal of trabecular meshwork in glaucoma patients.

LAser in Sltu Keratomileusis; refractive surgery in which the cornea is reshaped to change its optical power; corrects myopia, hyperopia, and astigmatism.

Visual Acuity of 20/200 or less, or visual field reduction to 20 degrees or less (in the better eye).

Any transparent material (often glass) that can bend light rays predictably.

Removal of the eye's natural lens.

Area where the cornea joins the sclera and the bulbar conjunctiva attaches to the eyeball.

– Lipiflow is a heat treatment for Meibomian Gland Dysfunction. It provides a warm and gentle heat to the eyelids while simultaneously applying a gentle massage. This combination effectively removes the blockages in the meibomian glands and allows them to secrete the clogged oil. After a session of LipiFLow treatment, the glands will be able to resume its natural production of oil for the tear film.

Also known as Normal-tension glaucoma; type of open-angle glaucoma in which a patient exhibits signs such as progressive disc cupping and visual field loss, but with normal intraocular pressure.

Distorted vision in which objects appear larger than normal.

The part of the retina responsible for the sharp, central vision needed to read or drive.

A group of conditions that include a deterioration of the macula causing a loss of central vision needed for sharp, clear eyesight. It is a leading cause of vision loss and blindness in those 65 years of age and older. Macular Degeneration is also called AMD or ARMD (age-related macular degeneration).

Swelling and cyst formation in the macula; can temporarily or permanently decrease vision.

Abnormality of the macula.

Loss of eyelashes often caused by chronic blepharitis.

Increased image size created through the use of optical devices.

Oil gland in the eyelid tissue that secretes the outer portion of the tear film; prevents rapid tear evaporation and tear overflow.

Corneal infection from overuse of contact lenses; caused by microorganisms.

Millimeters of mercury; units used to measure intraocular pressure.

Sweat glands near the eyelash follicles; infection can cause a stye.

Referring to one eye.

Multi-focal lenses let you focus on two or more distances through the same lens (usually distance, intermediate, and near). Also known as Bifocals, Trifocals, and Multifocals.

A condition cuased by an overpowered eye, which has too much optical power for its length, where distant objects appear less clearly and those objects up close are seen clearly. Also commonly referred to as "nearsighted."

Rise in intraocular pressure caused by narrow anterior chamber angles that prevent aqueous drainage.

Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.

Is a blocked tear duct that occurs when your nasal passageways cannot properly drain tear liquid from your eyes. You may have crusty, itchy, irritated or watery eyes. Sometimes, babies are born with blocked tear ducts.

National Contact Lens Examiners are certified professionals in Optometry who fit and work with contact lenses.

US National Drug Code; a standard code used to to identify FDA-approved drugs and biologicals.

Refractive error that allows the eye to see close-up objects clearly, but distance vision is blurred; myopia.

Corneal inflammation resulting from trauma or damage to corneal nerves; leads to cornea anesthesia.

Poor visual adaptation to the dark, resulting in reduced vision in low light; usually indicates defect in retinal rods.

Commonly called "night blindness," this is a condition that presents as impaired vision in dim light or darkness.

A functional defect in which the patient displays involuntary oscillating eye movements that are faster in one direction than the other.

Test that measures distance between various ocular structures (usually with A-scan or B-scan ultrasound instruments).

Elevated IOP, but with no evidence of optic disc or visual field changes; potential (but not definite) glaucoma suspect.

A valid and reliable instrument of 12 questions for measuring Dry Eye Disease and its effect on vision-related function.

Right eye.

The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual, irreversible vision loss.

Doctor of medicine (MD) or doctor of osteopathic medicine (DO) specializing in diagnosis and treatment of eye diseases and disorders.

Medical specialty dealing with function and disease of the eye.

Use of an ophthalmoscope to examine the internal structures of the eye.

The second cranial nerve that is the largest sensory nerve of the eye; carries sight information from the retina to the brain for processing.

Abnormality or degeneration of the optic nerve, not due to inflammation.

Vision care professional who makes and adjusts optical aids such as eyeglasses.

Retinal imaging that captures more than 80% of your retina in one panoramic image that allows your Optometrist to provide you with the most comprehensive eye exam possible by detecting underlying eye diseases and monitor treatment for existing ocular diseases.

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Doctor of optometry (OD) who specializes in vision problems and treatments.

Vision care specialty that deals with the detection and management of ocular disease.

Socket; cranial cavity of the skull that contains the eyeball.

“Ortho-K” is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the curvature of the cornea to temporarily improve the eye's ability to focus on objects. The lenses are worn at night to give clear vision during the day

Left eye.

Passage of aqueous fluid out of the eye through the anterior chamber angles.

Test to measure corneal thickness

Fibrous membrane that forms a protective layer between the eyelid and the bony orbit (socket)

Certified allied health professional in optometry; three levels are certified by CPO®: CPOA®, and CPOT®

Also known as year-round allergies, these are usually due to indoor allergies such as dust mites or mold

Area surrounding the eyeball

Side vision, created by stimuli falling on retinal areas that are far from the macula

Surgical procedure that uses ultrasound vibration to break up a cataract, making it easy to suction out of the eye

Refers to an eye that has its natural lens

Refers to lenses that automatically change from clear to dark in the presence of ultraviolet (UV) radiation.

Abnormal sensitivity to light; associated with discomfort and excessive tearing; often due to iritis or keratitis

Sensation of light or flashes from mechanical or electrical irritation of the retina (not from a light stimulus)

Refractive surgery that reshapes the corneal curvature with a laser after the surface of the cornea has been removed

Conjunctivitis; inflammation of the conjunctiva that is usually viral in origin; symptoms include discharge, grittiness, redness, and swelling

This is a lens material often used for minor prescriptions. Very few lenses are made from glass today, since glass is heavier, thicker, and can shatter. Also referred to as standard index or by the brand name CR-39.

This type of lens includes an invisible “polarized” filter that helps to cut down on blinding glare from reflective surfaces like water and snow for increased visual acuity (sharpness) in bright light conditions.

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Microspores of seed plants that can induce allergic or hypersensitivity reactions in some people

A lens material that is thinner, lighter, and more impact resistant than standard plastic. Polycarbonate lenses are the standard for children’s eyewear.

After cataract surgery, the rear lens capsule can cloud over; needs removal to improve vision

Space between the back of the iris and the front of the vitreous

Condition in which the aging crystalline lens (at around age 40) becomes less able to change shape to focus light at all distances, especially near vision. Presbyopia can be corrected with reading glasses, bi-focal glasses, or progressive lenses. Additional symptoms include eyestrain, headaches, and squinting.

The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual vision loss

Prism correction is used in eyeglasses for some people with diplopia, or double vision. The prism helps align the two images, so that only one image is seen.

As needed (as medication dosing)

Bi-focal or multi-focal lenses with no visible lines where the lens power gradually changes from distance to near. Also called PALs (Progressive Addition Lenses).

Itching

Unknown deposits appearing on the lens surfaces and other ocular structures; often associated with high intraocular pressure

A raised growth on the eye that is most often directly related to over-exposure to the sun. Dry, dusty conditions may also contribute to development of these growths. Protecting your eyes from UV radiation is a critical preventive measure.

Sagging upper eyelid

Device that measures intraocular pressure by blowing a puff of air against the cornea to flatten it

Plastic plug inserted into the punctum to prevent tear drainage, preserving tears to keep the eye moist

Corneal disease characterized by small corneal lesions of unknown origin

Black circular opening in the center of the iris that varies in size to regulate the amount of light that enters the eye

Pupillary distance (PD) is the distance between the pupils of your two eyes. It is an essential measurement when buying a new pair of prescription eyewear. For greatest comfort and clarity, these measurements should be taken by the optician involved in manufacturing the spectacles.

An instrument used to measure the distance between pupils. This measurement is used to position the eyeglass prescription correctly in front of the eye.

Once daily

Four times daily

Test to determine an eye’s refractive error and the best corrective lenses to be prescribed.

Optical defect in an unaccommodating eye; correctible with surgery, eyeglasses, or contact lenses

Light-sensitive tissue in the eye that converts images into electrical impulses that are sent to the brain via the optic nerve to interpret as vision. Consists of layers that include rods and cones.

Separation of the retina from the underlying pigment epithelium; usually caused by a retinal tear that leaks fluid from the vitreous and separates the retina

Retinal holes and tears are small breaks in the retina. Usually holes do not mean you will have serious vision problems right away. However, retinal holes and tears may cause problems if they allow fluid to seep behind the retina and cause the retinal layers separate from each other or detach from layers underneath.

Blockage of blood flow through the central retinal vein, causing a decrease in vision

Inflammation of the retina

Malignant tumor that develops from retinal visual cells

Any noninflammatory degenerative disease of the retina

Test that measures the eye’s refractive error

Gas permeable contact lenses are rigid lenses made of durable plastics that allow oxygen to pass through the lens.

These are cells inside the eye used by the retina to process light. Rods are used for low light levels (night vision), cones are used for sharp visual acuity and color perception.

Measures tear production with filter paper strips

Channel in the corneo-scleral junction that carries aqueous fluid from the anterior chamber to the bloodstream

Opaque protective outer layer of the eye (“the white”) that connects to the cornea and the sheath of the optic nerve

Scleral lenses are large-diameter gas permeable contact lenses that vault over the cornea (the clear front of the eye) and rest over the sclera (the white of the eye). The scleral lens provides a smooth optical surface that works to correct vision problems caused by keratoconus and other irregular cornea problems.

Inflammation of the sclera, often painful

Allergies, such as hay fever, that are seasonal in nature (eg, springtime or fall)

Types of lenses that correct one vision problem, like near or far-sightedness.

Chronic autoimmune disease often characterized by dry eyes, dry mouth, and arthritis

Microscope used to examine the eye; shows the cornea, lens, and clear fluids and membranes in layered detail

Surgical procedure in which a laser is used on the trabecular meshwork to increase aqueous outflow, reducing intraocular pressure

Lettered chart for measuring visual acuity; usually tested at 20 feet (hence, 20/20 vision)

This is the commonly seen eye chart often topped by a large letter “E” used in eye examinations. This measures your eye’s visual acuity, or the ability to see sharp detail clearly.

Sleepiness

Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness.

Sometimes called “crossed eyes” in young children, this condition is the lack of coordination between the eyes, such as one or both eyes turning in, out, up or down.

Acute pustular infection of oil glands located in an eyelash follicle

Rapid decrease in response to a given dose of a drug after repetitive administration.

Oil gland within the eyelid tissue; secretes the outer portion of the tear film to prevent tear evaporation and overflow

Tests the time between a blink and the development of a dry spot on the ocular surface; less than 10 seconds is abnormal.

Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.

Fluid secreted by the lacrimal glands to keep the conjunctiva and cornea moist.

Loss of pinkish tone in the optic disc; usually indicates optic nerve damage.

Three times daily.

Instrument that measures intraocular pressure; each type of tonometer measures pressure through slightly different means.

An optical device with a cylindrical component to correct astigmatism.

Structure inside the eye at the iris-scleral junction of the anterior chamber angle that filters aqueous fluid and controls its exit from the eye through Schlemm’s canal.

Surgical procedure to remove part of the trabecular meshwork to increase the outflow of aqueous fluid to treat elevated intraocular pressure.

Surgical procedure that uses a laser to burn part of the trabecular meshwork to increase outflow of aqueous fluid to treat elevated intraocular pressure.

Severe, chronic, and contagious infection of the eyelid and cornea caused by a virus; the leading cause of blindness in the world.

A condition caused by misdirected or abnormally positioned eyelashes. Trichiasis, sometimes caused by entropion causes discomfort and irritation to the eye, and can lead to permanent damage to the cornea and vision loss.

Optical device that incorporates lenses of 3 different powers.

Ocular defect that causes images to appear in triplicate; often caused by an early cataract

Light with wavelengths between 250 and 400 nanometers; invisible to the naked eye.

Commonly referred to as “UV Rays”, these are light waves that consist of both UVA and UVB rays from the sun. Without proper protection, chronic exposure to UV rays can lead to various eye conditions and damage.

Relates to a lens’ ability to filter out harmful rays of the sun. It is recommended that glasses block 100% of both UVA and UVB rays to minimize eye damage from the sun’s rays.

Pigmented vascular layers of the eye (iris, ciliary body, and choroid) that contain most of the eye’s blood vessels.

Inflammation of any of the structures of the uvea (iris, ciliary body, or choroid).

Ability of the eye to receive and transmit light images to the brain, where they are interpreted; the ability to see.

Assessment of the eye’s ability to distinguish object details and shape – numerically expressed as 20/20, 20/70, etc.

The full area visible to the eye when fixated straight ahead; measured in degrees.

Surgical removal of the vitreous.

Transparent gelatinous mass that fills the back two-thirds of the eyeball between the lens and retina.

Also known as perennial allergies, these are usually due to indoor allergies such as dust mites or mold.

Eye rotation away from the midline.

Blurred or distorted image quality resulting from the physical properties of an optical device (ie, lens)

Acanthamoeba Keratitis is a rare but serious infection of the eye that can result in permanent visual impairment or blindness. This infection is caused by a microscopic, freeliving ameba (single-celled living organism) called Acanthamoeba. Acanthamoeba causes Acanthamoeba Keratitis when it infects the transparent outer covering of the eye called the cornea. Acanthamoeba are very common in nature and can be found in bodies of water (for example, lakes and oceans), soil, and air. Anyone can get acanthamoeba keratitis, but it's most common in people who wear soft contact lenses. You have a greater risk of this condition if you: Swim or shower with contact lenses on or clean your contact lenses with tap water instead of disinfectant solution.

The eye’s increase in optical power in order to maintain image clarity as objects are moved closer

Additional lens power associated with your multifocal, bifocal, or progressive lens prescription needed to make it easier for you to read.

Eye rotation toward the midline

Refers to the extent to which a patient follows a doctor’s treatment regimen without close supervision

Additive treatment or medication that enhances the benefit of another treatment or medication

Group of conditions that include deterioration of the macula, resulting in a loss of sharp central vision; the most common cause of decreased vision after 50

Lack of tear production

Lack of pigment in the eyes, hair, and skin, which is usually associated with decreased visual acuity

An antigen that creates an allergic or hypersensitivity response

Inflammation of the conjunctiva from hypersensitivity to allergens

Argon laser trabeculoplasty; surgical procedure that uses a laser to create small burns in the trabecular meshwork to lower intraocular pressure

Also called lazy eye. Decreased vision in one eye that leads to the use of the other eye as the dominant eye. A problem most commonly associated with children.

Rise in intraocular pressure due to aqueous fluid behind the iris being unable to pass through the pupil; patients with anatomically narrow angles are predisposed to this condition

Loss of vision, particularly to part of the visual field

Space between the iris and innermost corneal surface that is filled with fluid

A lens treatment for your glasses that helps to reduce distracting glare and eye fatigue by reducing the amount of light reflecting off the lens surface and making the lenses appear clearer. Your eyes will also be more visible behind the lenses

Absence of the eye’s crystalline lens, such as after cataract extraction

Instrument that flattens the cornea to measure intraocular pressure

Clear fluid that fills the space in the eye between the cornea and the lens; maintains intraocular pressure and provides nourishment to the cornea, iris, and lens

Passage of aqueous fluid through the anterior chamber angle structures

Eyedrops with similar consistency to natural tears to alleviate Dry Eye symptoms

Refractive error that prevents the eye from focusing sharply, usually resulting from an abnormally shaped corneal surface; correctable by eyeglasses, contact lenses, or refractive surgery

The axis indicates the angle (in degrees) between the two meridians of an astigmatic eye. The axis is defined with a number from 1 to 180.

Inflammation of the conjunctiva caused by a bacterial infection; usually contagious.

Inflammation of the conjunctiva caused by a bacterial infection; usually contagious

Innermost layer of the choroid, directly under the retina; damage to the basal lamina is responsible for many bleeding disorders of the macula area

A number usually between 8 and 10 that conforms to the shape of your eye with your contact lens prescription.

Condition in which muscles of the brows, eyelids, and mouth are paralyzed by damage to the 7th cranial nerve; may cause affected eyelids to remain open, resulting in corneal drying

Twice daily

Eyeglasses that incorporate lenses of 2 different powers; allows for both near and far distance sight without changing eyewear

Referring to or affecting both eyes

Flap of tissue created to cover a sclero-corneal drainage channel during glaucoma surgery; enhances fluid outflow from the eye

Inflammation of the eyelids; may be caused by infection or allergy

Inflammation of the conjunctiva

Sudden, involuntary spasm causing uncontrolled blinking and squeezing of the eyelid

Non-seeing area within every visual field; caused by absence of photoreceptors where the optic nerve enters the eye

Inability to see

Periodic contraction of the eye muscles approximately every 5 seconds, causing the eyelid to close over the eye, spreading tears over the eye and limiting light entering the eye

Blue light blocking lenses offered at LensCrafters®. They offer two different options: one called Blue IQ™ lenses, which block about 52 percent of blue light, and another called Blue IQ Clear™ lenses, which block about 20 percent of blue light.

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Blue light is all around us. It comes primarily from the sun and it's what makes the sky look blue. Artificial blue light is also emitted by devices like computers, smartphones, flat-screen televisions LED lights, and energy-efficient light bulbs.

Incision to remove part of the lens capsule.

Incision to remove part of of the lens capsule

A cataract is a clouding of the crystalline lens of the eye that makes it hard for light to pass through and be focused properly. In a normal eye, the crystalline lens is almost transparent, however injury, age or disease can cause the lens to eventually loose its clarity. When the lens becomes 'opaque', it is called a cataract. Treatable by surgery.

First branch of the ophthalmic artery; provides nutrients to the inner two-thirds of the retina.

Collects retinal venous blood drainage and exits through the optic nerve.

Inflamed bump in the eyelid's meibomian gland.

Swelling of the conjunctiva.

Vascular Layer of the eye between the retina and sclera, providing nutrients to the outer layers of the retina.

Inflammation of the choroid.

Corneal/conjunctival dryness due to deficient tear production; keratoconjunctivitis sicca, Dry Eye syndrome.

Tissue in the eye that is involved in lens accommodation, intraocular pressure control, and producing the aqueous humor.

Collagen Cross-linking is procedure done to slow down the progression of Keratoconus. This treatment uses a combination of specially formulated eye drops and precisely applied UV light to create new bonds between the collagen fibers in your cornea. This strengthens and firms a cornea that has been weakened and thinned by keratoconus.

A lack of ability to distinguish certain colors. Commonly called "color blindness", the most common form of color deficiency is the inability to distinguish shades of red and green.

Refers to a patient following a doctor's treatment regimen.

High intraocular pressure, hazy corneas, and large eyes in children from newborn to 6 months old; developmental abnormalities prevent normal fluid drainage from the eye; requires surgical intervention.

Mucous membrane covering the outer surface of the eyeball (except the cornea) and inside surface of the eyelids.

Redness of the conjunctiva; associated with all types of conjunctivitis.

Pocket of conjunctiva between the upper eyelid and eyeball and lower eyelid and eyeball that permits the eyeball to rotate freely.

An eye condition caused by the inflammation of the conjunctiva, or clear membrane covering the white part of the eye and lining of the eyelids. The eyes will often appear swollen and red while also feeling gritty. It can be bacterial, viral, or allergic and could be contagious. Call or see your doctor to treat conjunctivitis.

Small disc worn on the cornea or sclera, providing visual correction of refractive errors.

Moving both eyes towards each other to maintain single binocular vision of an approaching object.

Displacement of the pupil from its normal position.

Transparent front of the eye covering the iris, pupil, and anterior chamber; provides the bulk of the eye's optical power.

Scraped area of the cornea accompanied by superficial tissue loss.

Central 3-5 mm where the cornea has the greatest curvature.

Hazy and swollen cornea.

Loss of the outer layer of the cornea because it fails to adhere to the Bowman's membrane.

Corneal hydrops is a complication of advanced keratoconus and is characterized by sudden onset of severe corneal opacification because of edema. The edema occurs from a spontaneous break in Descemet's membrane (one of the 5 layers of the cornea) because of the weakened cornea, leading to a sudden and painful decrease in visual acuity.

Use of dye such as fluorescein to reveal corneal epithelial defects.

Replacement of damaged or diseased cornea with donor corneal tissue.

Steroid used to treat inflammatory and allergic diseases.

The eye's natural lens located directly behind the iris. It has the ability to change shape to focus light rays onto the retina.

Optic cup; depression in the center of the optic disc that normally occupies less than one-third of the dis diameter.

Evaluates the progression of glaucoma by indicating the percentage of the disc occupied by the optic cup.

Abnormal enlargement of the optic cup, usually due to a long-term increase in intraocular pressure.

Use of a lens that produces different refractive power in each meridian; used to correct astigmatism.

Retinal swelling and cyst formation ion the macular area, can result in temporary or permanent decrease in vision.

Inflammation of the tear sac, often associated with poor tear drainage.

Awareness of relative spatial location of objects; perception of nearness and farness.

The leaking of retinal blood vessels into the macula in patients with diabetes, causing the macula to swell, which can temporarily or permanently decrease central vision.

Progressive retinal changes that accompany diabetes mellitus; this can progress from background retinopathy to proliferative retinopathy, which includes abnormal new blood vessels and fibrous tissue development.

The distance from one side of the lens to the other, usually around 13 to 15 millimeters that is associated with the size of your contact lenses.

Widening of the pupil.

Perception of two images from one object; double vision

Optic disc; ocular end of optic nerve

An eye condition that presents itself as itching, burning, and irritation of the eyes, is often called "dry eye syndrome". It is one of the most common problems treated by eye care professionals. It is usually caused by the breakdown (or deficiency) in the tears that lubricate the eyes. As we age, our bodies produce less oil to seal the eyes' watery layer. Hot, arid climates, air conditioning, certain medicines and irritants such as cigarette smoke can all increase dryness of the eye. Your eye care professional might prescribe "artificial tears" or other eye drops to help alleviate the problem.

Distorted shape of pupil.

Vertical skin fold at each side of the nose; hides the caruncle; present in infants before nose bridge is developed.

Overflow of tears down the face caused by poor tear drainage, excessive tearing, or outward turning of the lower eyelid.

Abnormal skin redness caused by capillary congestion under the skin.

Eye misalignment in which one eye turns inward while the other stays fixed straight ahead.

Procedure that removes the contents of the eyeball, leaving behind the sclera shell and, sometimes, the cornea; usually for reducing pain in a blind eye.

Eye misalignment in which one eye turns outward while the other stays fixed straight ahead.

Corneal irritation or inflammation caused by corneal drying due to incomplete closure of the eyelid.

Diseases that affect the cornea, sclera, conjunctiva, or eyelids.

Sense organ for sight.

One of the stiff hairs at the margin on the eyelid.

Structure covering the front of the eye that protects it, limits the light entering in, and distributes the tear film over the corneal structure.

The sclera and the cornea.

Refractive error that allows the eye to see clearly at a distance, but close-up images are blurred; hyperopia

Short-pulse laser that is used to create corneal flaps in refractive surgery.

Flashes are a visual sensation that can look like a camera flash going off or a lightning streak in your vision. Flashes occur because the vitreous or "jelly" is tugging on the retina. If the vitreous tugs too hard, it may cause a vision threatening event called a retinal tear or detachment. If you notice a sudden increase in the number of flashes you see, call your eye care professional.

A generalized term used to describe small specks moving subtly but noticeably in your field of vision. A floater or a spot is likely a tiny clump of gel or cells in the vitreous — the clear, jelly-like fluid inside your eye. Aging, eye injury and breakdown of the vitreous are the main causes of floaters and spots. If you notice a sudden increase in the number you see, call your eye care professional.

Colored dye that illuminates; used on the cornea to identify damage.

Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.

Position on the principal axis of a lens system where parallel light rays are brought to a point of focus.

Tiny elevations on the undersurface of the eyelids; associated with viral conjunctival inflammation.

The feeling of something in the eye; can be caused by an actual foreign body in the eye or by various damage or conditions.

A tiny spot in the center of the retina that contains only cone cells. This area is responsible for our sharpness of vision.

Interior posterior surface of the eyeball which includes the retina, optic disc, macula, and posterior pole.

Degenerative change that produces a white ring-shaped deposit of fat near the peripheral edge of the cornea; typically in patients over 60.

Clinical test that determines the extent to which a bright light shined in the eye changes visual acuity; evaluates the degree of visual impairment caused by a cataract.

A common cause of preventable vision loss that is due to damage to the optic nerve, the nerve that carries visual information from the eye to the brain. Treatable by prescription drugs or surgery.

The eyeball; a sensory organ that uses light to transmit visual information to the brain; 3 major layers in the globe include corneo-sclero, uvea, and retina.

Large mucous glands in the conjunctiva that secrete mucin, a component of precorneal tear film; can be damaged in Dry Eye sydrome.

Test that examines the anterior chamber angle structures through a special lens with a slit lamp.

Symptoms of the eye that may result with excessive thyroid-related concentration, including eyelid retraction, eyelid lag, corneal drying, and optic nerve inflammation.

Hazy ring seen around lights; can be a sign of a refractive error or optical defect such as cataract.

Eye infection caused by the herpes simplex virus. Results in inflammation and ulcers.

Having a different color iris in each eye.

A dense lens material that results in thinner, lightweight lenses than standard plastic. Index refers to index refraction which is the speed that light travels through the lens. Higher index lenses are available from 1.56 to 1.74 (the higher the number, the thinner the lens). They benefit people with stronger prescription eyeglasses.

Chemical that creates an allergic or inflammatory response.

Acute infection of oil glands of the eyelid; externally, also known as a stye; internally (in the meibomian glands), also known as a chalazion, if chronic.

Clinical sign; increased blood flow; usually refers to eye redness due to increased blood flow to the conjunctival blood vessels.

A condition where they eye is too short for its optical power causing distant objects to be seen clearly, yet objects close up are seen less clearly. Also commonly referred to as "farsighted."

Functional defect in which one eye deviates upward while the other remains straight and fixates normally.

Clinical sign; blood in the anterior chamber, often following blunt trauma to the eyeball.

Functional defect in which one eye deviates downward while the other remains straight and fixates normally.

Lens that may be surgically implanted to replace the eye's natural lens.

The pressure of fluid within the eye; elevated IOP is a treatable risk factor for glaucoma.

Removal of a portion of iris tissue.

Pigmented tissue behind the cornea that gives the eye its color and allows light to enter the eye by controlling the size of the pupillary opening; part of the uveal (middle) layer of the eye.

Inflammation of the iris, causing pain, tearing, blurring, small pupil, and red congested eye.

Equal vision in both eyes.

Surgical removal of corneal tissue.

Corneal inflammation; can be caused by a variety of infections, injuries, and unknown causes.

Corneal and conjunctival dryness due to deficient tear production; Dry Eye syndrome.

– Keratoconus is a condition that causes progressive weakening, thinning and cone-like bulging of the cornea. This irregularity in the shape of the cornea causes light rays hitting the cornea to become out of focus and results in blurry and distorted vision that cannot be corrected by wearing glasses. Distorted vision from Keratoconus can be corrected by special gas permeable contact lenses. Corneal damage from Keratoconus is not reversible however its progression can be slowed down and even halted completely by a procedure called Collagen Cross-linking. In severe cases of keratoconus, transplantation of the cornea may be necessary.

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Corneal melt; superficial corneal layers that "melt" away; often associated with severe inflammation, Dry Eye, or rheumatoid arthritis.

Surgical procedure on the cornea that usually refers to a corneal graft (replacing damaged corneal tissue with donor tissue).

Any incision into the cornea (surgical procedure).

Almond-shaped gland located above the eyeball in the upper outer region that produces tears.

Tear production; crying.

Acronym for Light Amplification by Stimulated Emission of Radiation; a high-energy light source that can cut, burn, or dissolve tissues for clinical procedures; used in many eye care procedures such as refractive surgery, treatment of diabetic retinopathy and macular degeneration, and removal of trabecular meshwork in glaucoma patients.

LAser in Sltu Keratomileusis; refractive surgery in which the cornea is reshaped to change its optical power; corrects myopia, hyperopia, and astigmatism.

Visual Acuity of 20/200 or less, or visual field reduction to 20 degrees or less (in the better eye).

Removal of the eye's natural lens.

Area where the cornea joins the sclera and the bulbar conjunctiva attaches to the eyeball.

– Lipiflow is a heat treatment for Meibomian Gland Dysfunction. It provides a warm and gentle heat to the eyelids while simultaneously applying a gentle massage. This combination effectively removes the blockages in the meibomian glands and allows them to secrete the clogged oil. After a session of LipiFLow treatment, the glands will be able to resume its natural production of oil for the tear film.

Also known as Normal-tension glaucoma; type of open-angle glaucoma in which a patient exhibits signs such as progressive disc cupping and visual field loss, but with normal intraocular pressure.

Distorted vision in which objects appear larger than normal.

The part of the retina responsible for the sharp, central vision needed to read or drive.

A group of conditions that include a deterioration of the macula causing a loss of central vision needed for sharp, clear eyesight. It is a leading cause of vision loss and blindness in those 65 years of age and older. Macular Degeneration is also called AMD or ARMD (age-related macular degeneration).

Swelling and cyst formation in the macula; can temporarily or permanently decrease vision.

Abnormality of the macula.

Loss of eyelashes often caused by chronic blepharitis.

Increased image size created through the use of optical devices.

Oil gland in the eyelid tissue that secretes the outer portion of the tear film; prevents rapid tear evaporation and tear overflow.

Corneal infection from overuse of contact lenses; caused by microorganisms.

Millimeters of mercury; units used to measure intraocular pressure.

Sweat glands near the eyelash follicles; infection can cause a stye.

Referring to one eye.

Multi-focal lenses let you focus on two or more distances through the same lens (usually distance, intermediate, and near). Also known as Bifocals, Trifocals, and Multifocals.

A condition cuased by an overpowered eye, which has too much optical power for its length, where distant objects appear less clearly and those objects up close are seen clearly. Also commonly referred to as "nearsighted."

Rise in intraocular pressure caused by narrow anterior chamber angles that prevent aqueous drainage.

Tear drainage channel from the lacrimal sac to the mucous membrane of the nose.

Is a blocked tear duct that occurs when your nasal passageways cannot properly drain tear liquid from your eyes. You may have crusty, itchy, irritated or watery eyes. Sometimes, babies are born with blocked tear ducts.

National Contact Lens Examiners are certified professionals in Optometry who fit and work with contact lenses.

US National Drug Code; a standard code used to to identify FDA-approved drugs and biologicals.

Refractive error that allows the eye to see close-up objects clearly, but distance vision is blurred; myopia.

Corneal inflammation resulting from trauma or damage to corneal nerves; leads to cornea anesthesia.

Poor visual adaptation to the dark, resulting in reduced vision in low light; usually indicates defect in retinal rods.

Commonly called "night blindness," this is a condition that presents as impaired vision in dim light or darkness.

A functional defect in which the patient displays involuntary oscillating eye movements that are faster in one direction than the other.

Test that measures distance between various ocular structures (usually with A-scan or B-scan ultrasound instruments).

Elevated IOP, but with no evidence of optic disc or visual field changes; potential (but not definite) glaucoma suspect.

A valid and reliable instrument of 12 questions for measuring Dry Eye Disease and its effect on vision-related function.

Right eye.

The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual, irreversible vision loss.

Doctor of medicine (MD) or doctor of osteopathic medicine (DO) specializing in diagnosis and treatment of eye diseases and disorders.

Medical specialty dealing with function and disease of the eye.

Use of an ophthalmoscope to examine the internal structures of the eye.

The second cranial nerve that is the largest sensory nerve of the eye; carries sight information from the retina to the brain for processing.

Abnormality or degeneration of the optic nerve, not due to inflammation.

Vision care professional who makes and adjusts optical aids such as eyeglasses.

Retinal imaging that captures more than 80% of your retina in one panoramic image that allows your Optometrist to provide you with the most comprehensive eye exam possible by detecting underlying eye diseases and monitor treatment for existing ocular diseases.

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Doctor of optometry (OD) who specializes in vision problems and treatments.

Vision care specialty that deals with the detection and management of ocular disease.

Socket; cranial cavity of the skull that contains the eyeball.

“Ortho-K” is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the curvature of the cornea to temporarily improve the eye's ability to focus on objects. The lenses are worn at night to give clear vision during the day

Left eye.

Passage of aqueous fluid out of the eye through the anterior chamber angles.

Test to measure corneal thickness

Fibrous membrane that forms a protective layer between the eyelid and the bony orbit (socket)

Certified allied health professional in optometry; three levels are certified by CPO®: CPOA®, and CPOT®

Also known as year-round allergies, these are usually due to indoor allergies such as dust mites or mold

Area surrounding the eyeball

Side vision, created by stimuli falling on retinal areas that are far from the macula

Surgical procedure that uses ultrasound vibration to break up a cataract, making it easy to suction out of the eye

Refers to an eye that has its natural lens

Refers to lenses that automatically change from clear to dark in the presence of ultraviolet (UV) radiation.

Abnormal sensitivity to light; associated with discomfort and excessive tearing; often due to iritis or keratitis

Sensation of light or flashes from mechanical or electrical irritation of the retina (not from a light stimulus)

Refractive surgery that reshapes the corneal curvature with a laser after the surface of the cornea has been removed

Conjunctivitis; inflammation of the conjunctiva that is usually viral in origin; symptoms include discharge, grittiness, redness, and swelling

This is a lens material often used for minor prescriptions. Very few lenses are made from glass today, since glass is heavier, thicker, and can shatter. Also referred to as standard index or by the brand name CR-39.

This type of lens includes an invisible “polarized” filter that helps to cut down on blinding glare from reflective surfaces like water and snow for increased visual acuity (sharpness) in bright light conditions.

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Microspores of seed plants that can induce allergic or hypersensitivity reactions in some people

A lens material that is thinner, lighter, and more impact resistant than standard plastic. Polycarbonate lenses are the standard for children’s eyewear.

After cataract surgery, the rear lens capsule can cloud over; needs removal to improve vision

Space between the back of the iris and the front of the vitreous

Condition in which the aging crystalline lens (at around age 40) becomes less able to change shape to focus light at all distances, especially near vision. Presbyopia can be corrected with reading glasses, bi-focal glasses, or progressive lenses. Additional symptoms include eyestrain, headaches, and squinting.

The most common type of glaucoma caused by the slowing of normal aqueous outflow from the eye; can result in gradual vision loss

Prism correction is used in eyeglasses for some people with diplopia, or double vision. The prism helps align the two images, so that only one image is seen.

As needed (as medication dosing)

Bi-focal or multi-focal lenses with no visible lines where the lens power gradually changes from distance to near. Also called PALs (Progressive Addition Lenses).

Itching

Unknown deposits appearing on the lens surfaces and other ocular structures; often associated with high intraocular pressure

A raised growth on the eye that is most often directly related to over-exposure to the sun. Dry, dusty conditions may also contribute to development of these growths. Protecting your eyes from UV radiation is a critical preventive measure.

Sagging upper eyelid

Device that measures intraocular pressure by blowing a puff of air against the cornea to flatten it

Plastic plug inserted into the punctum to prevent tear drainage, preserving tears to keep the eye moist

Corneal disease characterized by small corneal lesions of unknown origin

Black circular opening in the center of the iris that varies in size to regulate the amount of light that enters the eye

Pupillary distance (PD) is the distance between the pupils of your two eyes. It is an essential measurement when buying a new pair of prescription eyewear. For greatest comfort and clarity, these measurements should be taken by the optician involved in manufacturing the spectacles.

An instrument used to measure the distance between pupils. This measurement is used to position the eyeglass prescription correctly in front of the eye.

Once daily

Four times daily

Test to determine an eye’s refractive error and the best corrective lenses to be prescribed.

Optical defect in an unaccommodating eye; correctible with surgery, eyeglasses, or contact lenses

Light-sensitive tissue in the eye that converts images into electrical impulses that are sent to the brain via the optic nerve to interpret as vision. Consists of layers that include rods and cones.

Separation of the retina from the underlying pigment epithelium; usually caused by a retinal tear that leaks fluid from the vitreous and separates the retina

Retinal holes and tears are small breaks in the retina. Usually holes do not mean you will have serious vision problems right away. However, retinal holes and tears may cause problems if they allow fluid to seep behind the retina and cause the retinal layers separate from each other or detach from layers underneath.

Blockage of blood flow through the central retinal vein, causing a decrease in vision

Inflammation of the retina

Malignant tumor that develops from retinal visual cells

Any noninflammatory degenerative disease of the retina

Test that measures the eye’s refractive error

Gas permeable contact lenses are rigid lenses made of durable plastics that allow oxygen to pass through the lens.

These are cells inside the eye used by the retina to process light. Rods are used for low light levels (night vision), cones are used for sharp visual acuity and color perception.

Measures tear production with filter paper strips

Channel in the corneo-scleral junction that carries aqueous fluid from the anterior chamber to the bloodstream

Opaque protective outer layer of the eye (“the white”) that connects to the cornea and the sheath of the optic nerve

Scleral lenses are large-diameter gas permeable contact lenses that vault over the cornea (the clear front of the eye) and rest over the sclera (the white of the eye). The scleral lens provides a smooth optical surface that works to correct vision problems caused by keratoconus and other irregular cornea problems.

Inflammation of the sclera, often painful

Allergies, such as hay fever, that are seasonal in nature (eg, springtime or fall)

Types of lenses that correct one vision problem, like near or far-sightedness.

Chronic autoimmune disease often characterized by dry eyes, dry mouth, and arthritis

Microscope used to examine the eye; shows the cornea, lens, and clear fluids and membranes in layered detail

Surgical procedure in which a laser is used on the trabecular meshwork to increase aqueous outflow, reducing intraocular pressure

Lettered chart for measuring visual acuity; usually tested at 20 feet (hence, 20/20 vision)

This is the commonly seen eye chart often topped by a large letter “E” used in eye examinations. This measures your eye’s visual acuity, or the ability to see sharp detail clearly.

Sleepiness

Sphere indicates the amount of lens power prescribed to correct nearsightedness or farsightedness.

Sometimes called “crossed eyes” in young children, this condition is the lack of coordination between the eyes, such as one or both eyes turning in, out, up or down.

Light with wavelengths between 250 and 400 nanometers; invisible to the naked eye.

Commonly referred to as “UV Rays”, these are light waves that consist of both UVA and UVB rays from the sun. Without proper protection, chronic exposure to UV rays can lead to various eye conditions and damage.

Relates to a lens’ ability to filter out harmful rays of the sun. It is recommended that glasses block 100% of both UVA and UVB rays to minimize eye damage from the sun’s rays.

Pigmented vascular layers of the eye (iris, ciliary body, and choroid) that contain most of the eye’s blood vessels.

Inflammation of any of the structures of the uvea (iris, ciliary body, or choroid).

Ability of the eye to receive and transmit light images to the brain, where they are interpreted; the ability to see.

Assessment of the eye’s ability to distinguish object details and shape – numerically expressed as 20/20, 20/70, etc.

The full area visible to the eye when fixated straight ahead; measured in degrees.

Surgical removal of the vitreous.

Transparent gelatinous mass that fills the back two-thirds of the eyeball between the lens and retina.

Also known as perennial allergies, these are usually due to indoor allergies such as dust mites or mold.