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Glossary

Below is a glossary of terms related to eye disease and common refractive errors.

Age-Related Macular Degeneration (AMD)
An eye disease that gradually destroys the macula, the part of the eye that provides sharp, central vision needed for seeing objects clearly.

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Amblyopia
Amblyopia is the medical term used when the vision of one eye is reduced because it fails to work properly with the brain. The eye itself looks normal, but for various reasons the brain favors the other eye. This condition is also sometimes called lazy eye.

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Anophthalmia and Microphthalmia
Anophthalmia and microphthalmia are often used interchangeably. Microphthalmia is a disorder in which one or both eyes are abnormally small, while anophthalmia is the absence of one or both eyes.

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Astigmatism
Astigmatism is a common type of refractive error where the eye does not focus light evenly onto the retina. The cornea of a normal eye is curved like a basketball, with the same degree of roundness in all areas. An eye with astigmatism has a cornea that is curved more like a football, with some areas that are steeper or more rounded than others. This can cause images to appear blurry and stretched out.

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Behçet’s Disease of the Eye
Behçet’s disease is an autoimmune disease that results from damage to blood vessels throughout the body, particularly veins. The four most common symptoms are mouth sores, genital sores, inflammation inside of the eye, and skin problems. Inflammation inside of the eye (uveitis, retinitis, and iritis) occurs in more that half of those with Behçet’s disease and can cause blurred vision, pain, and redness. This disease is also known as adamantiades.

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Bietti’s Crystalline Dystrophy
Bietti’s crystalline dystrophy (BCD) is an inherited eye disease which tends to lead to progressive night blindness and visual field constriction. This disease is also known as Bietti’s crystalline corneoretinal dystrophy.

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Blepharitis
Blepharitis is a common condition that causes inflammation of the eyelids.

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Blepharospasm
Blepharospasm is associated with an abnormal function of the basal ganglion from an unknown cause. The basal ganglion is the part of the brain responsible for controlling the muscles. Blepharospasm causes abnormal, involuntary blinking or spasm of the eyelids.

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Cataract
A cataract is a clouding of the lens in the eye that affects vision. Most cataracts are related to aging. A cataract can occur in either or both eyes. It cannot spread from one eye to the other.

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Coloboma
Coloboma is used to describe conditions where normal tissue in or around the eye is missing from birth.

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Conjunctivitis (pinkeye)
This term describes a group of diseases that cause swelling, itching, burning, and redness of the conjunctiva, the protective membrane that lines the eyelids and covers exposed areas of the sclera, or white of the eye.

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Diabetic Retinopathy
Diabetic retinopathy is the most common diabetic eye disease and is caused by changes in the blood vessels of the retina. In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina.

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Dry Eye
Dry eye occurs when the eye does not produce tears properly, or when the tears are not of the correct consistency and evaporate too quickly.

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Floaters
Floaters are little “cobwebs” or specks that float about in your field of vision. They are small, dark, shadowy shapes that can look like spots, thread-like strands, or squiggly lines. They move as your eyes move and seem to dart away when you try to look at them directly. They do not follow your eye movements precisely, and usually drift when your eyes stop moving.

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Fuchs’ Dystrophy
Fuchs’ dystrophy is a slowly progressing disease that usually affects both eyes and occurs when endothelial cells gradually deteriorate without any apparent reason. As more endothelial cells are lost over the years, the endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision. Eventually, the epithelium also takes on water, resulting in pain and severe visual impairment.

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Glaucoma
Glaucoma is a group of diseases that damage the eye’s optic nerve and can result in vision loss and blindness.

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Histoplasmosis
Histoplasmosis is a disease caused when airborne spores of the fungus Histoplasma capsulatum are inhaled into the lungs, the primary infection site. Histoplasmosis can later cause a serious eye disease called ocular histoplasmosis syndrome (OHS).

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Hyperopia (farsightedness)
Hyperopia, also known as farsightedness, is a common type of refractive error where distant objects may be seen more clearly than objects that are near.

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Iridocorneal Endothelial Syndrome
Iridocorneal endothelial syndrome is actually a grouping of three closely linked conditions: iris nevus (or Cogan-Reese) syndrome; Chandler’s syndrome; and essential (progressive) iris atrophy. The most common feature of this group of diseases is the movement of endothelial cells off the cornea onto the iris. This loss of cells from the cornea often leads to corneal swelling, distortion of the iris, and variable degrees of distortion of the pupil, the adjustable opening at the center of the iris that allows varying amounts of light to enter the eye. This cell movement also plugs the fluid outflow channels of the eye, causing glaucoma.

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Keratoconus
Keratoconus is a disorder which causes a progressive thinning of the cornea. Keratoconus arises when the middle of the cornea thins and gradually bulges outward, forming a rounded cone shape. This abnormal curvature changes the cornea’s refractive power, producing moderate to severe distortion (astigmatism) and blurriness (nearsightedness) of vision.

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Lattice Dystrophy
Lattice dystrophy gets its name from an accumulation of amyloid deposits, or abnormal protein fibers, throughout the middle and anterior stroma. Over time, the lattice lines will grow opaque and involve more of the stroma. They will also gradually converge, giving the cornea a cloudiness that may also reduce vision.

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Macular Hole
A macular hole is a small break in the macula, located in the center of the eye’s light-sensitive tissue called the retina.

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Macular Pucker
A macular pucker is scar tissue that has formed on the eye’s macula, located in the center of the light-sensitive tissue called the retina.

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Map-Dot-Fingerprint Dystrophy
Map-Dot-Fingerprint dystrophy occurs when the epithelium’s basement membrane develops abnormally. When the basement membrane develops abnormally, the epithelial cells cannot properly adhere to it. This causes recurrent epithelial erosions, in which the epithelium’s outermost layer rises slightly, exposing a small gap between the outermost layer and the rest of the cornea.

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Myopia
Myopia, also known as nearsightedness, is a common type of refractive error where close objects appear clearly, but distant objects appear blurry.

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Ocular Herpes
Herpes of the eye, or ocular herpes, is a recurrent viral infection that is caused by the herpes simplex virus.

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Presbyopia
Presbyopia is a common type of vision disorder that occurs as you age. It is often referred to as the aging eye condition. Presbyopia results in the inability to focus up close, a problem associated with refraction in the eye.

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Pterygium
A pterygium is a pinkish, triangular-shaped tissue growth on the cornea.

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Refractive Error
A Refractive error occurs when the shape of the eye prevents light from focusing directly on the retina.

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Retinal Detachment
The retina is the light-sensitive layer of tissue that lines the inside of the eye and sends visual messages through the optic nerve to the brain. When the retina detaches, it is lifted or pulled from its normal position.

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Retinoblastoma
Retinoblastoma is a type of cancer that forms in the retina (the light-sensitive tissue at the back of the eye).

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Retinopathy of prematurity (ROP)
Retinopathy of prematurity (ROP) is a potentially blinding eye disorder that primarily affects premature infants weighing about 2¾ pounds or less that are born before 31 weeks of gestation.

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Stevens-Johnson Syndrome
Stevens-Johnson Syndrome (SJS), also called erythema multiforme major, is a disorder of the skin that can also affect the eyes. SJS can cause serious eye problems, such as severe conjunctivitis; iritis, an inflammation inside the eye; corneal blisters and erosions; and corneal holes.

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Usher Syndrome
Usher syndrome is the most common condition that affects both hearing and vision. One major symptom of Usher syndrome is an eye disorder called retinitis pigmentosa, or RP. Retinitis pigmentosa causes night-blindness and a loss of peripheral vision through the progressive degeneration of the retina.

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Uveitis
Uveitis is a general term describing a group of inflammatory diseases that produces swelling and destroys eye tissues.

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Vitreous Detachment
Vitreous detachment is a common condition where  the vitreous slowly shrinks, and these fine fibers pull on the retinal surface. Usually the fibers break, allowing the vitreous to separate and shrink from the retina. Vitreous is a gel-like substance that helps the eye maintain a round shape. There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina, the eye’s light-sensitive tissue.

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