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Glossary

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vision diagnostics chairAblation Removal - is the surgical removal of eye tissue to correct the eye’s ability to refract light.

Accommodation – the eye's ability to automatically change focus from seeing at one distance to seeing at another.

Accommodation Disorder - accommodation disorders have a variety of causes. Symptoms include blurred vision, double vision, eye strain, headache, fatigue and difficulty concentrating (particularly while reading).

Amaurosis Fugax - sudden and usually temporary vision loss caused by an "eye stroke", a clot or blockage disrupts blood flow to the eye, symptoms can include curtain-like darkness, usually in just one eye.

Amblyopia - also known as “lazy eye” is the undeveloped central vision in one eye that leads to the use of the other eye as the dominant eye. There are no symptoms. The patient may be found squinting and closing one eye to see; there may be unrecognized blurred vision in one eye and vision loss.

AMD or ARMD – (Age-related Macular Degeneration) a disorder characterized by the gradual loss of central vision due to a damaged macula (which is made up of retinal cones necessary for sight).

Aniridia – the absence or partial absence of the iris is typically congenital. Additional symptoms include poor vision and photophobia.

Anisocoria – an unequal pupil size. Causes could include glaucoma, head or eye trauma, an intracranial tumor, infection of the membranes surrounding the brain and previous intraocular surgery. A small percent of the population has unequal-sized pupils naturally (without any known cause).

Anterior Chamber – a part of the eye located behind the cornea and in front of the iris and lens.

Aphakia - Absence of the eye's crystalline lens, a condition that occurs after cataract extraction

Aqueous Humor – a clear fluid in the front of the eye, between the cornea and the iris, that provides nutrients to the cornea and the lens. The fluid is produced by the tissue and muscle surrounding the eye. Glaucoma causes difficulty in draining this fluid, and pressure builds up. The result is damage to the optic nerve and loss of vision.

Visibly Better officeArcus - an opaque arc or ring around the peripheral cornea, this represents fatty or oily deposits in the cornea. It is usually seen in elderly people and is called Arcus Senilis. Arcus juvenilis is seen in people younger than 40 and often indicates high levels of cholesterol in the blood.

Argyll Robertson Pupil – a small, irregular pupil that does not react to any type of light, but does respond when the eye has to focus on a nearby object.

Asteroid Hyalosis - a harmless condition that creates suspended particles within the eye's interior, detectable by a doctor during an exam. Floaters are not usually associated with this condition. These yellowish particles made of fats rarely interfere with vision or cause symptoms. The particles move within the eyes and resemble stars at night. The condition is not well understood, but generally is associated with aging.

Astigmatism – a condition in which the eye is shaped like a football or egg instead of a baseball. Light rays are focused at two points on the retina rather than one, resulting in blurred vision. Additional symptoms include distorted vision, eyestrain, shadows on letters, squinting and double vision.

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Best Corrected Visual Acuity (BCVA) - the best vision you can achieve with correction such as glasses, is measured on the standard Snellen eye chart. For example, if your uncorrected eyesight is 20/150, but you can see 20/20 with glasses, your BCVA is 20/20.

Bifocals - lens with one segment for near vision and one segment for far vision. This feature can be applied to both eyeglass lenses and contact lenses.

Blepharitis - inflammation of the eyelid(s), typically around the eyelashes. Various types of dermatitis, rosacea and allergic reactions can cause Blepharitis. Symptoms include a red or pink eyelid, crusty lid or lashes, burning, foreign body sensation, eye or eyelid pain or discomfort, dry eyelid, dry eye, eyelash loss, grittiness, stickiness, eyelid swelling and tearing.

Blepharochalasis - excessive, drooping eyelid skin caused by recurring swelling. This condition typically occurs in young people.

Blepharoconjunctivitis - inflammation of the eyelid and conjunctiva. Infections and allergic reactions are among the causes. Symptoms include a red or pink eye, a red or pink eyelid, pain or discomfort of the eye or around the eye, tearing, burning, eye dryness and eye stickiness.

Blepharospasm - involuntary increased blinking that progress to spasms in both eyes. The exact cause is unknown, but it is believed to be a central nervous system disorder. It can result in a functional blindness since the patient can't open his or her eyes long enough to function visually.

Blind spot – A sightless area within the normal visual field of an eye, caused by the absence of light sensitive photoreceptors where the optic nerve enters the eye.

Bowman's Membrane – the corneal layer between the epithelium and the stroma.

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Canaliculus - are tiny channels at the beginning of tear ducts through which tears drain until they exit into the nose.

Canaliculitis - inflammation of a tear duct (or ducts), caused by a bacterial infection. Symptoms of this disorder include discharge, a red or pink eye and a swollen upper or lower eyelid near the nose.

Cataract - clouding of the natural lens of the eye, usually caused by aging in conjunction with other risk factors, such as exposure to the sun's UV rays, smoking, steroid intake and diabetes. Symptoms include blurred vision, glare, halos around lights, colors that are less bright, a cloudy spot in your vision and, sometimes, temporary vision improvement.

Cellulitis - inflammation of tissue around the eye. Pre-septal cellulitis affects the lid and other outer areas of the eye, symptoms include a red, swollen lid, swelling around the eyes and eye or lid pain or discomfort. Orbital cellulitis affects the inner areas around the eyeball, symptoms include a bulging eye, as well as a red, swollen lid, swelling around the eyes, eye or lid pain or discomfort and a decrease in vision.

Visibly Better EyechartCentral Retinal Artery - First branch of the ophthalmic artery whose purpose is to supply nutrition to the inner two-thirds of the retina.

Central Retinal Vein - Blood vessel that collects retinal venous blood drainage and then exits the eye through the optic nerve.

Central Serous Retinopathy – a disorder which fluid collects under the central retina (macular area), disrupting central vision. The cause is unknown. Symptoms include blurred central vision and metamorphopsia. Floaters can also develop in some patients.

Central Vision - The eye's best vision used for reading and discerning fine detail and color.

Chalazion - a small bump on the eyelid caused by an obstructed gland. Symptoms include light sensitivity, tearing and eyelid swelling. Chalazia are usually not painful unless they become infected.

Choroid - layers of blood vessels located between the sclera (white of the eye) and the retina; they provide nourishment to the back area of the eye.

Choroidal Neovascularization – an abnormal growth of new blood vessels in the choroid, commonly associated with macular degeneration, but it can occur as a result of other eye conditions as well. Symptoms include vision loss and metamorphopsia.

CK (Conductive Keratoplasty) - procedure in which a surgeon uses radio waves to heat collagen in the cornea's periphery to shrink it and reduce hyperopia (farsightedness).

CMV Retinitis (cytomegalovirus retinitis) - serious eye infection usually found in those with auto-immune conditions, such as AIDS patients; symptoms include floaters, blind spots, blurry vision and vision loss.

Eye Exam EquipmentColor Blindness – a partial or total inability to distinguish specific colors usually inherited, and is much more common in men than in women.

Computer Vision Syndrome - collection of problems, mostly eye- and vision-related, associated with computer use. Symptoms include eyestrain, dry eyes, blurred vision, red or pink eyes, burning, light sensitivity, headaches and pain in the shoulders, neck and back.

Cone - a photosensitive receptor in the retina that helps you see color.

Conjunctiva - the clear, thin mucous membrane that lines the "white" of the eye (sclera) and the inner surface of the eyelid.

Conjunctivitis - inflammation of the conjunctiva, characterized by a pink eye. The cause is either infectious or allergic, though the term "pink eye" is commonly used for any type of conjunctivitis. Other symptoms include burning, discharge, dryness, itching, light sensitivity, eye pain or discomfort, stickiness, and tearing.

Contact Lens Problem - contact lens problems can range from minor to sight-threatening, and include protein build-up, debris on the lens, a ripped or nicked lens, infections and more. Symptoms can include frequent blinking, blurred vision, burning, discharge, foreign body sensation, itching, light sensitivity, eye pain or discomfort, a red or pink eye or lid and eyelid swelling.

Contrast Sensitivity - the ability of the eye to detect the line of demarcation between an object and its background or an adjacent object.

Convergence – the eyes' ability to turn inward. People with convergence insufficiency have trouble (eyestrain, blurred vision, etc.) with near tasks such as reading.

Cornea - the clear part of the eye covering the iris and pupil; it lets light into the eye, permitting sight.

Corneal Abrasion - a loss of the epithelial layer of the cornea due to minor trauma such as contact lens trauma, another foreign body, or a sports injury. Symptoms include blurred vision, foreign body sensation, grittiness, light sensitivity, eye pain or discomfort, a red or pink eye and tearing.

Corneal Dystrophy - one of a group of conditions, usually hereditary, in which the cornea loses its transparency. The corneal surface is no longer smooth. Symptoms include blurred vision, foreign body sensation, light sensitivity, eye pain or discomfort and vision loss.

Corneal Edema - swelling of the eye's cornea; causes include intraocular surgery, corneal dystrophies, and high intraocular pressure and contact lens complications. Symptoms include vision loss, halos around lights, and a white or cloudy spot on the eye, photophobia, eye pain and foreign body sensation.

Corneal Erosion - recurrent breakdown of the corneal epithelium typically caused by a previous corneal abrasion or by map-dot-fingerprint dystrophy. Symptoms include blurred vision, foreign body sensation and eye pain or discomfort.

Closeup of Human EyeCorneal Implants - devices (rings or contacts) placed in the eye, usually to correct vision.

Corneal Opacity - a cloudy spot in the cornea that is normally transparent. Causes include corneal scar tissue and infection. Symptoms include halos around lights, photophobia, vision loss and a white or cloudy spot on the eye.

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

Corneal Ulcer - an infected corneal abrasion frequently found in extended wear contact lens users. A corneal ulcer is an ocular emergency. Symptoms include light sensitivity, eye pain or discomfort, a red or pink eye, a white or cloudy spot on the eye and tearing.

Crystalline lens - The eye's natural lens which is transparent, biconvex intraocular tissue and helps bring rays of light to a focus on the retina. Cystoid Macular Edema (CME) - swelling of the eye's macula, caused by an excessive amount of fluid.

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Applying Contact Lens SolutionDiabetic Retinopathy – The range of retinal changes accompanying long-standing diabetes mellitus. The first stage is background retinopathy. Can advance to proliferative retinopathy, which includes the growth of abnormal new blood vessels (neovascularization) and fibrous tissue.

Dry Eye Syndrome - Corneal and conjunctival dryness due to deficient tear production. Occuring predominantly in menopausal and post-menopausal women. Can cause foreign body sensation, burning eyes, filamentary keratitis, and erosion of conjunctival and corneal epithelium. This can be a temporary or permanent condition.

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Environmental Condition - air pollution, wind and bright light can irritate your eyes and cause symptoms such as burning, dryness and tearing.

Esotropia - cross-eyes. Eye misalignment where one eye deviates inward (toward nose) while the other fixates normally.

Exotropia - wall-eyes. Eye misalignment where one eye deviates outward (away from nose) while the other fixates normally.

Extended Wear - contact lenses that are FDA-approved to be worn without removal for up to seven days (or 30 days in the case of one brand), meaning some people will be comfortable sleeping with the contacts in. Thirty-day contact lenses are sometimes referred to as "continuous wear."

Extraocular Muscles - Six muscles that move the eyeball (lateral rectus, medial rectus, superior oblique, inferior oblique, superior rectus, inferior rectus).

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Farsightedness - also called hyperopia. To farsighted people, near objects are blurry, but far objects are in focus.

Floaters - A darkish gray spot or speck that passes across your field of vision and moves as you move your eye. Floaters are very common and may look like clouds, strands, webs, spots, squiggles, wavy lines or other shapes.

Foreign Body - something in the eye or on the eye that doesn't belong, symptoms include foreign body sensation, eye pain or discomfort, a red or pink eye, tearing, frequent blinking, blurred vision, discharge, light sensitivity and vision loss.

Fundus - Interior posterior surface of the eyeball; includes retina, optic disc, macula, posterior pole. Viewed with an ophthalmoscope.

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Glaucoma – a disease characterized by elevated intraocular pressure, which causes optic nerve damage and subsequent peripheral vision loss. Most people have no initial symptoms of chronic (open-angle) glaucoma, but you can develop peripheral vision loss, headaches, blurred vision, difficulty adapting to darkness and halos around lights.

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Keratoconus – A hereditary degenerative corneal disease affecting vision. Characterized by generalized thinning and cone-shaped protrusion of the central cornea, typically occurs in both eyes.

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LASIK (Laser-Assisted In Situ Keratomileusis) - surgical procedure in which a tiny flap is cut in the top of the cornea, underlying corneal tissue is removed with an excimer laser, and the flap is put back in place. LASIK corrects myopia, hyperopia, astigmatism, and presbyopia through monovision.

Low Vision - also called partial sight, 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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Myopia - also called Nearsightedness is a condition in which the length of the eye is too long, causing light rays to focus in front of the retina rather than on it, resulting in blurred distance vision. Additional symptoms include eyestrain, poor night vision and squinting.

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Neovascularization - Abnormal formation of new blood vessels, usually in or under the retina, or sometimes on the iris surface. This can develop in diabetic retinopathy, blockage of the central retinal vein, or macular degeneration.

Nystagmus - Involuntary, rhythmic side-to-side or up and down (oscillating) eye movements that are faster in one direction than the other.

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Closeup of Human EyeOptic Nerve - Largest sensory nerve of the eye whose role is to carry impulses for sight from the retina to the brain.

Orthoptics - Field of Study dealing with the diagnosis and treatment of defective eye coordination, binocular vision and functional amblyopia by non-medical and non-surgical methods (glasses, prisms, exercises, etc)

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Peripheral Vision - Side vision elicited by stimuli falling on retinal areas distant from the macula.

Photophobia - Abnormal light sensitivity. May be associated with excessive tearing. Most often due to inflammation of the iris or cornea.

Progressive Lenses - also called progressive addition lenses or PALs. Multifocal lenses whose corrective powers change progressively throughout the lens. A wearer looks through one portion of the lens for distance vision, another for intermediate vision, and a third portion for reading or close work. Each area is blended invisibly into the next, without the lines that traditional bifocals or trifocals have.

Ptosis – Drooping or sagging of the upper eyelid. May be congenital or caused by paralysis or weakness of the 3rd cranial nerve or sympathetic nerves.

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Retina - the sensory membrane that lines the back of the eye. Cells in the retina called photoreceptors transform light energy into electrical signals that are transmitted to the brain by way of the optic nerve.

Retinal Detachment - Separation of the retina from the underlying pigment epithelium. This causes a disruption of the visual cell structure and markedly disturbs vision. Almost always caused by a retinal tear; often requires immediate surgical repair.

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Strabismus - Eye misalignment caused by extraocular muscle imbalance. Causing one fovea is not directed at the same object as the other.

Sty, Stye - Acute pustular infection of the oil glands of Zeis, located in an eyelash follicles.