Eye Dictionary

Accommodation  the ability of the eye to change its focus from distant objects to near objects.

Acuity  clearness, or sharpness of vision.

Astigmatism  a distortion of the image on the retina caused by irregularities in the cornea or lens.

Cornea  the clear, front part of the eye. The cornea is the first part of the eye that bends (or refracts) the light and provides most of the focusing power.

Diopter  the measurement of refractive error.  A negative diopter value signifies an eye with myopia and positive diopter value signifies an eye with hyperopia.

Dry Eye Syndrome  a common condition that occurs when the eyes do not produce enough tears to keep the eye moist and comfortable. Common symptoms of dry eye include pain, stinging, burning, scratchiness, and intermittent blurring of vision.

Endothelium  the inner layer of cells on the inside surface of the cornea.

Epithelium  the outermost layer of cells of the cornea and the eye's first defense against infection.

Farsightedness  the common term for hyperopia.

Ghost Image  a fainter second image of the object you are viewing.

Glare  scatter from bright light that decreases vision.

Halos are rings around lights due to optical imperfections in or in front of the eye.

Haze  corneal clouding that causes the sensation of looking through smoke or fog.

Hyperopia  the inability to see near objects as clearly as distant objects, and the need for accommodation to see distant objects clearly.

Inflammation  the body's reaction to trauma, infection, or a foreign substance, often associated with pain, heat, redness, swelling, and/or loss of function. 

Informed Consent Form  a document disclosing the risks, benefits, and alternatives to a procedure.

Iris  the colored ring of tissue suspended behind the cornea and immediately in front of the lens.

Keratitis  inflammation of the cornea.

Kerato  prefix indicating relationship to the cornea.

Keratoconus  a disorder characterized by an irregular corneal surface resulting in blurred and distorted images.

LASIK  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. Please refer to www.lasikmd.com for more info.

Lens  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.

Monovision  the purposeful adjustment of one eye for near vision and the other eye for distance vision.

Myopia the inability to see distant objects as clearly as near objects.

Nearsightedness  the common term for myopia.

Ophthalmologist  a medical doctor specializing in the diagnosis and medical or surgical treatment of visual disorders and eye disease.

Optician  an expert in the art and science of making and fitting glasses and may also dispense contact lenses.

Optometrist  a primary eye care provider who diagnoses, manages, and treats disorders of the visual system and eye diseases.

Overcorrection  a complication of refractive surgery where the achieved amount of correction is more than desired.

PRK  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. Please refer to www.lasikmd.com for more info.

Presbyopia  the inability to maintain a clear image (focus) as objects are moved closer. Presbyopia is due to reduced elasticity of the lens with increasing age.

Pupil  a hole in the center of the iris that changes size in response to changes in lighting.  It gets larger in dim lighting conditions and gets smaller in brighter lighting conditions.

Refraction  a test to determine the refractive power of the eye; also, the bending of light as it passes from one medium into another.

Refractive Errors  hyperopia, myopia, and astigmatism.

Refractive Power  the ability of an object, such as the eye, to bend light as light passes through it.

Retina  a layer of fine sensory tissue that lines the inside wall of the eye. The retina acts like the film in a camera to capture images, transforms the images into electrical signals, and sends the signals to the brain.

Sclera  the tough, white, outer layer (coat) of the eyeball that, along with the cornea, protects the eyeball.

Snellen Visual Acuity Chart  one of many charts used to measure vision.

Stroma  the middle, thickest layer of tissue in the cornea.

Undercorrection  a complication of refractive surgery where the achieved amount of correction is less than desired.

Visual Acuity  the clearness of vision; the ability to distinguish details and shapes.

Vitreous Humor  the transparent, colorless mass of gel that lies behind the lens and in front of the retina and fills the center of the eyeball.