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In reading about vision and eye care, you may come across a number of unfamiliar terms. This glossary, adapted from the U.S. Food and Drug Administration and the National Eye Institute of the National Institutes of Health, can help you decipher some of them. For more information, read about "The Eye" "Eye Exams" "Cataracts" "Glaucoma" "Macular Degeneration" "Eyes and Sun" "Amblyopia" "Retinitis Pigmentosa" "Refractive Errors". For additional questions, of course, ask your doctor.
Ablate in surgery is to remove. Ablation zone is the area of tissue that is removed during laser surgery.
Accommodation is the ability of the eye to change its focus from distant objects to near objects.
Acuity is clearness or sharpness of vision.
Amblyopia is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye. (Read about "Amblyopia")
Astigmatism is a distortion of the image on the retina usually caused by irregularities in the cornea. (Read about Astigmatism in "Refractive Errors")
Cataract is a clouding of the eye's lens that can cause vision problems. The most common type is related to aging, with more than half of all Americans age 65 and older having a cataract. (Read about "Cataracts")
Cornea is the clear front part of your eye. The cornea is the first part of the eye that bends (or focuses) the light and provides most of the focusing power. (Read about "Refractive Errors")
Diabetic retinopathy is a potentially blinding complication of diabetes that damages the eye's retina. It affects half of all Americans diagnosed with diabetes. (Read about "Diabetes")
Diopter is the measurement of refractive error. When used in excimer refractive surgery, diopter is a measurement of the refractive power of the eye. In LASIK and other refractive procedures, a negative diopter value signifies an eye with myopia and positive diopter value signifies an eye with hyperopia. (Read about "Refractive Errors")
Dry Eye is a common condition that occurs when the eyes do not produce enough tears to keep the eye wet and comfortable. Common symptoms of dry eye include feelings of stinging, burning or scratchiness of the eyes. (Read about "Dry Eye")
Endothelium is the inner layer of cells on the inside surface of the cornea.
Epithelium is the outermost layer of cells of the cornea and is the eye's first defense against infection.
Excimer laser is an ultraviolet laser used in refractive surgery to remove corneal tissue. (Read about "Refractive Errors")
Farsightedness is the common term for hyperopia. (Read about Hyperopia in "Refractive Errors")
FDA is the abbreviation for the Food and Drug Administration. The FDA is the United States government agency responsible for the evaluation and approval of medical devices.
Fovea is the region of the retina with the highest concentration of special retinal nerve cells, called cones, that produce sharp, daytime vision.
Glaucoma is an eye disease in which the normal fluid pressure inside the eyes slowly rises, leading to vision loss or even blindness. (Read about "Glaucoma")
Ghost Image is a fainter second image of the object you are viewing.
Glare is scatter from bright light that decreases vision.
Halos are rings around lights.
Haze is corneal clouding that causes the sensation of looking through smoke or fog.
Hyperopia is the inability to see near objects more clearly than distant objects. (Read about Hyperopia in "Refractive Errors")
Inflammation is a tissue's reaction to trauma often associated with pain, heat, redness, swelling and/or loss of function. Inflammation may be caused by mechanical trauma, infections, bacteria, viruses, immune reactions or other causes. (Read about "Microorganisms" "The Immune System")
In Situ means "in place" or not removed.
Iris is the colored ring of tissue suspended behind the cornea and immediately in front of the lens.
Keratectomy is the surgical removal of corneal tissue.
Keratotomy is a surgical incision (cut) of the cornea.
Keratitis is the inflammation of the cornea. ((Read about "Keratitis")
Kerato is the prefix indicating relationship to the cornea.
Keratomileusis is the carving of the cornea formerly done with a lathe and blade and now done with an excimer laser.
Laser is an acronym for light amplification by stimulated emission of radiation. A laser is an instrument that produces a powerful beam of light and can vaporize tissue.
LASIK is the acronym for laser assisted in situ keratomileusis, which refers to creating a flap in the cornea with a microkeratome and using a laser to reshape the underlying cornea. (Read about LASIK in "Refractive Errors")
Lens is a part of the eye that provides some focusing power. The lens is able to change shape allowing the eye to focus at different distances.
Macular degeneration or age-related macular degeneration (AMD) is a disease that affects central vision; it's a common cause of vision loss among people over age of 60. (Read about "Macular Degeneration")
Microkeratome is a surgical device that is affixed to the eye by use of a vacuum ring. When secured, a very sharp blade shaves a small amount of the cornea at a predetermined depth.
Monovision is the purposeful adjustment of one eye for near vision and the other eye for distance vision.
Myectomy is a surgical procedure to remove some of the muscles and nerves of the eyelids.
Myopia the inability to see distant objects clearly. (Read about Myopia in "Refractive Errors")
Nearsightedness is the common term for myopia. (Read about Myopia in "Refractive Errors")
Ocular histoplasmosis syndrome is a leading cause of vision loss in Americans ages 20 to 40. It affects a small percentage of people who contract the fungal infection. OHS develops when abnormal blood vessels grow underneath the retina.
Ophthalmologist is a medical doctor specializing in the diagnosis and medical or surgical treatment of visual disorders and eye disease.
Optician is an expert in the art and science of making and fitting glasses and may also dispense contact lenses.
Optometrist is a primary eye care provider who diagnoses and manages disorders of the visual system and eye disease.
Overcorrection is a complication of refractive surgery where the expected amount of correction is more than desired and often occurs where healing regresses less vigorously than predicted.
PRK is the acronym for photorefractive keratectomy, which is a procedure involving the removal of the surface layer of the cornea (epithelium) by gentle scraping and use of a computer-controlled excimer laser to reshape the stroma.
Presbyopia is part of the normal process of aging. As a person becomes older, one begins to lose the flexibility of the lens of the eye, which limits the ability of the eye to change its point of focus from distance to near. (Read about Presbyopia in "Refractive Errors")
Pupil is what appears as a small black dot in the center of the iris and changes its diameter in response to ambient lighting.
Radial Keratotomy is a surgical procedure designed to correct myopia (nearsightedness) by flattening the cornea and is commonly referred to as RK.
Refraction is a test to determine the best eyeglasses or contact lenses to correct a refractive error (myopia, hyperopia, astigmatism) OR the bending of light by the use of a lens or other material.
Refractive Errors are hyperopia, myopia, astigmatism and presbyopia. (Read about "Refractive Errors")
Retina is the part of the eye that lines the inside wall of the eye and consists of fine sensory tissue, which acts as the film in a camera that captures and transmits images. (Read about "The Eye")
Retinitis Pigmentosa (RP) is a group of diseases that affect the very delicate and thin tissue that makes up the retina. (Read about "Retinitis Pigmentosa")
Sclera is the tough, white, outer layer (coat) of the eyeball and, with the cornea, protects the entire eyeball.
Snellen Visual Acuity refers to one of many charts used to measure vision (black and white with an "E" at the top).
Stroma is the thick, middle layer of cells in the cornea.
Undercorrection is a complication of refractive surgery where the expected amount of correction is less than desired and often occurs where healing regresses more vigorously than predicted.
Usher syndrome is an inherited disorder that involves loss of both hearing and vision. (Read about "Usher Syndrome")
Visual Acuity is simply the clearness of vision or the ability to distinguish details and shapes or objects.
Vitreous Humor is the transparent, colorless mass of gel that lies behind the lens and in front of the retina and fills the center of the eyeball.
All Concept Communications material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.
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