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Glossary of Eye Care Terms

General

Retina

 

Accommodation

(uh-kah-muh-DAY-shun). Increase in optical power by the eye in order to maintain a clear image (focus) as objects are moved closer. Occurs through a process of ciliary muscle contraction and zonular relaxation that causes the elastic-like lens to "round up" and increase its optical power. Natural loss of accommodation with increasing age is called presbyopia.

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After-Cataract, Secondary Cataract

Remnants of an opaque lens remaining in the eye, or opacities forming, after extracapsular cataract removal.

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Age Related Macular Degeneration (AMD)

Macular degeneration is one of the leading causes of decreased vision in the United States. It is a slowly progressive disease with a highly variable and unpredictable course. Most cases (80%) are sporadic (not hereditary) and only 20% seem to occur in family clusters. People with AMD do not go completely blind but get blurred central vision. When the disease is advanced, a person may not be able to read, see faces, drive or see the TV well, but they can live independently and do most daily tasks. Read More

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ALK

See automated lamellar keratoplasty.

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Amblyopia (lazy eye)

(am-blee-OH-pee-uh), "lazy eye." Decreased vision in one or both eyes without detectable anatomic damage in the eye or visual pathways. Usually uncorrectable by eyeglasses or contact lenses.

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Amsler Grid

The Amsler grid (a piece of white paper with lines on it in a grid pattern), is used to aid in the detection of significant macular symptoms. The grid is positioned 14 inches from the eye on a flat surface which is well-lighted. Appropriate reading glasses or bifocals should be worn. While the eye focuses on the dark spot in the center of the grid, the horizontal and vertical lines in the peripheral vision should appear straight, and the squares formed by these lines should not be distorted. See the Grid

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A-Scan

Type of ultrasound, radar-like device that emits very high frequency waves that are reflected by the ocular structures and converted into electrical impulses. Used for differentiating normal and abnormal eye tissue or for measuring length of eyeball.

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Automated Lamellar Keratoplasty

Excision of the outer corneal layers (lamellae) with a computer controlled keratome (knife), usually as a part of a refractive keratoplasty procedure.

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Background Retinopathy

See diabetic retinopathy.  

Bifocals

Eyeglasses that incorporate two different powers in each lens, usually for near and distance corrections.

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Blepharitis

(blef-uh-RI-tus). Inflammation of the eyelids, usually with redness, swelling, and itching.

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Cataracts

Blurred vision from cataracts is a common vision problem. Fortunately, surgery is available to remove the cataract and restore good vision. Read More

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Cataract Extraction

Removal of a cloudy lens from the eye. An extracapsular cataract extraction leaves the rear lens capsule intact; with an intracapsular extraction there is complete removal of lens with its capsule, usually by cryoextraction.

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Central Retinal Artery

First branch of the ophthalmic artery; supplies nutrition to the inner two-thirds of the retina.

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Central Retinal Vein

Blood vessel that collects retinal venous blood drainage; exits the eye through the optic nerve.

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Chalazion

(kuh-LAY-zee-un). Inflamed lump in a meibomian gland (in the eyelid). Inflammation usually subsides, but may need surgical removal. Sometimes called an internal hordeolum.

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Conjunctivitis

(kun-junk-tih-VI-tis), "pink eye." Inflammation of the conjunctiva. Characterized by discharge, grittiness, redness and swelling. Usually viral in origin, but may be bacterial or allergic; may be contagious.

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Diabetic Retinopathy

Diabetes, especially after prolonged duration, may produce diabetic retinopathy in some patients. This is a serious and potentially blinding eye condition. Diabetic retinopathy is the number one cause of legal blindness in the country in patients under 64. Read More

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Diabetic Laser Treatment

Laser treatment (photocoagulation) uses powerful light rays directed into the eye and focused on a tiny spot on the retina. The light produces heat, which destroys abnormal tissue and cauterizes or seals off the abnormal blood vessels. Photocoagulation is usually not painful and is performed in our office as an outpatient procedure. Read More

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Diabetic Macular Edema

The retina is the layer of nerve tissue at the back of the eye upon which light is focused. The retina then converts light into signals which are sent to the brain where vision is perceived. The central portion of the retina is called the macula, and it is this area which is responsible for our sharpest central (reading) vision. Small blood vessels travel through the retina supplying it with oxygen and removing waste products. Read More

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Diplopia, Double Vision

Perception of two images from one object; images may be horizontal, vertical or diagonal.

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Drusen

(DRU-zin). Tiny, white hyaline deposits on Bruch's membrane (of the retinal pigment epithelium). Common after age 60; sometimes an early sign of macular degeneration.

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Dry Eye

Dry eye is a common eye disorder that causes symptoms such as dryness, burning, heaviness, tired eyes, headache or intermittent blurring. It is common in this part of the country because of the dry atmospheric conditions. Eyes may feel worse in the late afternoon and after activities such as reading, computer work, driving or TV watching. Symptoms are also more common as we get older.

Dry eye has many causes that are all related to dysfunction of the tear film. If this protective barrier is inadequate, the surface of the eye dries out. Most dry eye is unrelated to medical problems, but autoimmune disorders such as Lupus, sarcoidosis and rheumatoid arthritis may be the underlying cause. Antihistamines, high blood pressure medications, birth control pills, some antibiotics and vitamin A deficiency may also cause the problem. A thorough evaluation is often necessary to determine the cause.

Treatment usually involves the use of various artificial tears. These may need to be used many times a day. Sometimes an underlying disease must be treated to get adequate relief. In some cases, relief can only be attained by plugging the tear ducts surgically or with punctal plugs.

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Ectropion

(ek-TROH-pee-un). Outward turning of the upper or lower eyelid so that the lid margin does not rest against the eyeball, but falls or is pulled away. Can create corneal exposure with excessive drying, tearing, and irritation. Usually from aging.

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Entropion

(en-TROH-pee-un). Inward turning of upper or lower eyelid so that the lid margin rests against and rubs the eyeball.

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Exotropia

(eks-oh-TROH-pee-uh), walleyes. Eye misalignment in which one eye deviates outward (away from nose) while the other fixates normally.

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Floaters

Particles that float in the vitreous and cast shadows on the retina; seen as spots, cobwebs, spiders, etc. Occurs normally with aging or with vitreous detachment, retinal tears, or inflammation.

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Fluoresceine Retinal Angiography

This test evaluates the blood flow in the eye. Since many retinal diseases are vascular in nature, fluoresceine angiography is an invaluable tool in the evaluation and treatment of retinal problems.

The test is safe and is performed in our in-office angiography suite. Fluoresceine dye is injected into a vein and photographs are taken as it flows through the back of the eye. Fluoresceine dye fluoresces when exposed to cobalt blue light. Using the proper illumination and selective barrier filters in the camera, rapid sequence photographs of the retinal and choroidal circulation can be obtained. For your convenience, the film is developed in our high speed automated processor in about 20 minutes.

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Fovea

(FOH-vee-uh). Central pit in the macula that produces sharpest vision. Contains a high concentration of cones and no retinal blood vessels.

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Glaucoma

Glaucoma is an eye condition characterized by the build up of pressure within the eye causing damage to the main nerve of the eye resulting in loss of vision and potentially blindness. Read More

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Hyperopia

(hi-pur-OH-pee-uh), farsightedness. Focusing defect in which an eye is underpowered. Thus light rays coming from a distant object strike the retina before coming to sharp focus, blurring vision. Corrected with additional optical power, which may be supplied by a plus lens (spectacle or contact) or by excessive use of the eyes own focusing ability (accommodation).

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Hyphema

(hi-FEE-muh). Blood in the anterior chamber, such as following blunt trauma to the eyeball.

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Intraocular Pressure

Fluid pressure inside the eye.

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IOL (intraocular lens)

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

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Keratoconus

(kehr-uh-toh-KOH-nus). Degenerative corneal disease affecting vision. Characterized by generalized thinning and cone-shaped protrusion of the central cornea, usually in both eyes. Hereditary.

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Laser Surgery

Lasers are surgical tools that use precise, controllable and safe, high energy light to treat eye diseases. Since lasers are light, and the eye is designed to let in light, lasers can be used to treat eye disease without cutting. Lasers can restore or stabilize vision and prevent severe loss of vision in many situations. They can also be used cosmetically to remove wrinkles and scars, and to improve the quality of life by correcting nearsightedness, farsightedness and astigmatism.

Laser surgery is convenient and usually painless. It is an out-patient, state-of- the-art procedure that is usually done in our office. All of our physicians and technical staff are specialty trained in laser procedures.

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LASIK

Laser Assisted In-Situ Keratomileusis (LASIK) is a brief outpatient microsurgical procedure that reduces the amount of nearsightedness by flattening or steepening the cornea of the eye. Since 1949, Dr. Jose Barraquer of Bogota, Columbia had been working on a procedure to reshape the cornea by removing an outer layer of the cornea, reshaping it, and replacing it onto the eye. In the late 1980's Dr. Luis Ruiz, also of Bogota, refined the corneal shaping technique by introducing the Automated Corneal Shaper. The microkeratome is used to shave a thin flap from the front surface of the cornea. This is called Lamellar surgery because the cornea, similar to a piece of plywood, is composed of many layers and this flap of tissue is composed of only a few layers of the anterior cornea.

In the mid 1980's the Excimer Laser was developed for the correction of refractive errors. This is a cold laser that utilizes ultraviolet light energy to reshape the corneal surface that it touches. It is considered to be extremely precise and predictable. This procedure is called Phototheraputic Keratectomy or PRK, and while a large number of patients have undergone this procedure with very good results, this procedure has some limitations. Following surface treatment with the Excimer laser, there is a raw area left on the surface of the cornea that must heal before clear vision can occur. This raw area also can result in increased pain, blurring, and variable effect of healing which can affect the amount of correction achieved. Also, a layer of the cornea called Bowman's membrane is removed; this can cause increased corneal haze and scarring in higher amounts of myopia. Like RK, PRK is also more variable and unpredictable in higher amounts of nearsightedness. The F.D.A. (Food and Drug Administration) approved the Excimer laser in 1995 for surface PRK in low to moderate amounts of nearsightedness.

In 1991 the Microkeratome was combined with the Excimer laser and the current technique of LASIK was developed. During the procedure, a suction ring is placed onto the eye to stabilize it, and the microkeratome is used to form a thin flap of corneal tissue. The Excimer laser is then used to gently sculpt the cornea, removing a very precise amount of tissue from the cornea underneath this flap, and the flap is carefully replaced back into position without sutures. By removing a variable amount of tissue from the middle of the cornea, this causes the overlying flap to drape down into the space flattening the central cornea. This central area of cornea, which is removed with the laser, varies in thickness depending on the patients amount of nearsightedness. LASIK has the advantage of laser precision, without leaving a raw surface of the cornea. This translates into decreased post-operative discomfort, and quicker visual recovery with LASIK over PRK. For astigmatism, since the curvature of the cornea is steeper in one part of the cornea and flatter in another, like a football, the laser also can treat the steeper areas of the cornea more than the flatter areas effectively reshaping the cornea into a more rounded or spherical shape. Every eye is unique, therefore careful preoperative examinations are conducted to develop a surgical plan for each patient. The VISX excimer laser has been approved for the treatment of nearsightedness, farsightedness, and astigmatism. Recently the Visx Excimer laser was also approved for LASIK by the F.D.A.. The VISX laser is one of only 2 lasers which is approved for both PRK and LASIK.

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Legal Blindness

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

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Low Vision

Term usually used to indicate vision of less than 20/200.

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Macula

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

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Macular Hole

Macular holes are small (100 to 700 micron), full thickness defects in the central macula (fovea). They usually occur spontaneously in older people, especially women. Trauma and macular edema (swelling) are less common causes of macular holes. Since the fovea is critical for visual function, a small defect has a profound affect on vision.

Macular holes are diagnosed by a clinical exam from your retinal specialist. Special contact lens evaluation and special photography may also be helpful.

Until recently there was no treatment for macular holes. Fortunately, recent advances in retinal surgery have allowed us to close the retinal defect and restore vision in many people. The surgery is called vitrectomy. Microsurgical instruments are used to remove the gel (vitreous) from the inside of the eye. Any scar tissue on the surface of the retina is then meticulously dissected away. The fluid in the eye is replaced with a special gas (sulfahexafluoride) and an additional compound (often your own serum) may then be placed on the hole to induce healing. After surgery the patient must meticulously look at the floor for approximately ten days. The anatomic success for hole closure ranges between 80 and 90%. If the hole closes there is an 80 to 90% chance of visual improvement.

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Myopia

(mi-OH-pee-uh), nearsightedness. Focusing defect in which the eye is overpowered. Light rays coming from a distant object are brought to focus in front of the retina. Requires a minus lens correction to "weaken" the eye optically and permit clear distance vision.

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Neovascularization

(nee-oh-VAS-kyu-lur-ih-ZAY-shun). Abnormal formation of new blood vessels, usually in or under the retina or on the iris surface. May develop in diabetic retinopathy, blockage of the central retinal vein, or macular degeneration.

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Nystagmus

(ni-STAG-mus). 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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Ocular Histoplasmosis

Ocular histoplasmosis is an eye infection which can lead to permanent loss of central (reading) vision in one or both eyes. Histoplasma capsulatum is a fungus that is prevalent in the Mississippi and Ohio river valleys. The fungus is so common in these regions that 80% of children, over five years of age, will have positive laboratory evidence of having been infected. Over 99% of these infections do not cause symptoms. If systemic symptoms do occur, they are typical of those that occur with the flu. The infection gains access to the body through the lungs and enters the bloodstream, where the fungus spreads to different body organs, including the eye. The infection lasts two days to two weeks and resolves usually without any eye symptoms. The infection often leaves small scars in the back of the eye.

If scars are present in or near the macula, the patient is at risk to lose vision. The macula is that portion of the retina responsible for our reading vision. These scars may remain inactive for a lifetime or they may "activate" many years later and cause symptoms. "Activation" of scar tissue does not represent a new infection. For reasons that are not fully understood, new blood vessels develop in the choroid and extend beneath the retina. This process is called choroidal neovascularization. These new vessels can leak fluid or bleed and cause symptoms (blurred vision, etc.). If this occurs in the center of the macula, permanent loss of central vision may result.

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Ophthalmologist

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

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Optic Disc, Optic Nerve Head

Ocular end of the optic nerve. Denotes the exit of retinal nerve fibers from the eye and entrance of blood vessels to the eye.

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Optician

(ahp-TISH-un). Professional who makes and adjusts optical aids, e.g., eyeglass lenses, from refraction prescriptions supplied by an ophthalmologist or optometrist.

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Phacoemulsification

(fay-koh-ee-mul-sih-fih-KAY-shun). Use of ultrasonic vibration to shatter and break up a cataract, making it easier to remove.

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Photophobia

(foh-toh-FOH-bee-uh). Abnormal sensitivity to, and discomfort from, light. May be associated with excessive tearing. Often due to inflammation of the iris or cornea.

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Pinguecula

(pin-GWEK-yu-luh). Yellowish-brown subconjunctival elevation composed of degenerated elastic tissue; may occur on either side of the cornea. Benign.

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"Pink Eye"

See conjunctivitis.

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Pneumatic Retinopexy

Pneumatic retinopexy is a newer procedure for retinal re-attachment. Freezing treatment is placed around the retinal tears. Then, a temporary gas bubble is injected into the eye. This closes the retinal tears and a scleral buckle is not used. The subretinal fluid is not surgically drained, but is pumped out by the retinal pigment epithelial cells. This procedure will not work for all retinal detachments, but can be done with local anesthetic in our office. See Scleral Buckling, Vitrectomy.

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Presbyopia

(prez-bee-OH-pee-uh). Refractive condition in which there is a diminished power of accommodation arising from loss of elasticity of the crystalline lens, as occurs with aging. Usually becomes significant after age 45.

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PRK (Photorefractive Keratectomy)

The Excimer laser has been used very successfully to treat patients with myopia since 1987. Since that time over 1,500,000 patients have been treated with the laser. Photorefractive Keratectomy or PRK is a method to precisely sculpt the surface of the cornea using a state of the art, computer controlled, invisible, cool beam of light energy to reshape the corneal surface that it touches. Since October of 1995, the FDA has approved PRK for the treatment of low to moderate amounts of myopia and astigmatism. PRK is considered to be safe and predictable. Each pulse of the laser removes approximately 25 microns (0.00004 of an inch) of corneal tissue, which makes it extremely accurate. The more removed, the more refractive effect is achieved. In less than a minute, the laser removes less than 50 microns of tissue, which is about ½ the thickness of a human hair, to achieve the proper correction. After this treatment, most people report that they no longer need to depend on glasses or contact lenses. In the clinical trials, 64% of people reported 20/20 or better vision after PRK and more than 93% of people could see 20/40 or better, reporting that they were much more functional and could even drive a car without glasses or contact lenses. Although vision without glasses improved for all eyes, some still needed glasses or contact lenses for some tasks after surgery.

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Progressive Addition Lens (PAL), Progressive-Power Lens

Eyeglass lens that incorporates corrections for distance vision through midrange, to near vision (usually in lower part of lens), with smooth transitions and no bifocal demarcation line.

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Poliferative Retinopathy

See diabetic retinopathy.

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Pterygium

(tur-IH-jee-um). Abnormal wedge-shaped growth on the bulbar conjunctiva. May gradually advance onto the cornea and require surgical removal. Probably related to sun irritation.

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Ptosis

(TOH-sis). Drooping of upper eyelid. May be congenital or caused by paralysis or weakness of the 3rd cranial nerve or sympathetic nerves, or by excessive weight of the upper lids.

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Refraction

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

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Retina

The retina is a thin layer of neural tissue that lines the inside of the eyeball and is analogous to the film in a camera. Images are focused onto the retina, where the light is converted into signals which are sent to the brain where vision is perceived. The macula is the central 3 to 4 millimeters of the retina and is responsible for central vision. This area is predisposed to many macular diseases. The fovea is the central 300 to 500 microns of the macula and provides us with our sharpest reading vision. A small area of damage to the fovea can have a profound affect on vision.

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Retinal Detachment

When a retina detaches, or peels away from its support tissue (the retinal pigment epithelium - RPE) the condition is called a retinal detachment. If the retina remains detached, the eye will go blind.

There are two main types of retinal detachment -- serous and rhegmatogenous. Serous detachments are less common and are caused by fluid leaking underneath the retina. This can be caused by tumors, abnormal blood vessels, infections and inflammation. These are treated by treating the underlying disease process.

Rhegmatogenous retinal detachments occur when the vitreous (the clear gel that fills the eye) shrinks and pulls on the weak peripheral retina resulting in a retinal tear. Not all tears lead to retinal detachment. However, in about 30% of cases, vitreous fluid flows through the tear and seeps behind the retina, causing the retina to detach.

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Retinal Vein Occlusion

A retinal vein occlusion means that a vein in the retina (the lining of the eye that senses light) has become blocked. Since veins drain blood out of tissues, a blockage means that the affected area will not have adequate blood flow. The vessel will leak and the tissue will swell (edema).

If a small branch vein occludes, the damage to the retina is more limited. If the entire retinal vein (the central retinal vein) becomes blocked, the visual loss varies but may be severe.

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Retinitis Pigmentosa

Retinitis Pigmentosa (RP) is a group of progressive inherited diseases that are characterized by poor vision in dim light and constricted field of vision. Symptoms can occur at any age, but typically start in the teens or twenties. The rate of disease progression is variable. It can be inherited as an autosomal dominant, autosomal recessive or X-linked recessive trait, or may occur as isolated simplex cases. RP represents many different genetic mutations that share common phenotypic features. Usually, only the eyes are affected, but other diseases may be associated. The disease affects roughly 1 in 4000 Americans.

There is no reliable treatment for retinitis pigmentosa. Fortunately, the disease is one of the most actively researched genetic diseases in the world, and treatments may be available in the next several years.

For more information about retinitis pigmentosa and current research, visit the Foundation Fighting Blindness (formerly the RP Foundation) web site at www.blindness.org.

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Scleral Buckling

The most common (and the oldest) surgery for retinal re-attachment is scleral buckling. This is a major surgery that often requires general anesthesia and must be done in the operating room. In this surgery, freezing treatment is placed around each retinal hole and the fluid is drained out from under the retina by creating a hole through the white part of the eye (sclera). Next, a silicone band is sewn around the eye to create a scleral buckle. This relieves vitreo-retinal traction by indenting the eye and reducing the eye's circumference. See Pneumatic Retinopexy, Vitrectomy.

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Trifocal

(TRI-foh-kul). Eyeglass lens that incorporates three lenses of different powers. The main portion is usually focused for distance (20 ft.), the center segment for about 2 ft., and the lower segment for near (14 in.).

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20/20

Normal visual acuity. Upper number is the standard distance (20 feet) between an eye being tested and the eye chart; lower number indicates that a tested eye can see the same small standard-sized letters or symbols as a normal eye at 20 feet.

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Uveitis

Uveitis is a group of rather uncommon conditions in which the uvea, or vascular coat of the eye, is inflamed. The part of the uvea we are all familiar with is the iris (colored part of the eye). Uveitis takes many forms ranging from benign inflammation of the iris (iritis) to severe sight and even life threatening diseases. The causes of these inflammations include infection, trauma, surgery, and auto-immune diseases. In auto immune diseases, the body's defense mechanisms, which normally attack foreign agents (such as bacteria and viruses), attack the body -- in this case the uvea. Strong anti-inflammatory medicines are often required to save vision and possibly ones life if a severe auto-immune disease is present.

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Visual Acuity

Assessment of the eye's ability to distinguish object details and shape, using the smallest identifiable object that can be seen at a specified distance (usually 20 ft. or 16 in.).

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Visual Field

Full extent of the area visible to an eye that is fixating straight ahead.

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Vitrectomy

For complicated retinal detachments, vitrectomy is used. In this major surgical procedure, micro surgical instruments are used to fix the retinal detachment from the inside of the eye. Traction is released from the retina by removing the vitreous and microsurgically dissecting any scar tissue. The subretinal fluid is drained through a hole in the retina and laser is used to seal the tears. A gas bubble or silicone oil is used to hold the retinal in place while it heals. See Scleral Buckling, Pneumatic Retinopexy.

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Vitreoretinal Disease

Any disease or condition that affects the inside of the eye, especially the vitreous or the retina, is considered a vitreoretinal disease.

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Vitreous

The vitreous is the clear gel-like substance that fills the eye. Its maintains the shape of the eye and allows transmission of light from the external environment to the retina which lies immediately behind the vitreous.

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Vitreous Detachment

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

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Excerpted from Dictionary of Eye Terminology, copyright 1990-2006 by Barbara Cassin and Triad Communications. Reprinted with permission.