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Eye Care Glossary

Eye Care Glossary


Ablation zone: the area of tissue that is removed during laser surgery.
Accommodation: the ability of the eye to change its focus from distant objects to near objects.
AcrySof® ReSTOR® IOL: multifocal lens that can treat patients with both cataracts and presbyopia.
Acuity: clearness, or sharpness of vision.
Astigmatism: a distortion of the image on the retina caused by irregularities in the cornea or lens. In astigmatism, light is not brought into a sharp point of focus.


Bladeless LASIK: a laser device, rather than an actual blade, is used to create a corneal flap for LASIK surgery.


Cataracts: a cataract is a clouding that develops in the lens of the eye, varying in degree from slight to complete opacity and obstructing the passage of light.
Conductive keratoplasty: also known as CK, it is a type of refractive surgery that uses radio waves to adjust the contour of the cornea.
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.
Crystalens®: an artificial lens implant that, unlike a standard IOL, can treat both a person’s cataracts and presbyopia.
CustomVue™: custom-tailored laser vision correction procedure designed to correct the unique imperfections of your eyes.


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


Endothelium: the 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.
Excimer laser: an ultraviolet laser used in refractive surgery to remove corneal tissue.


Farsightedness: the common term for hyperopia.


Ghost image: a fainter second image of the object you are viewing.
Glare: scatter from bright lights that decrease vision making it difficult seeing in the presence of bright light.
Glaucoma: a group of eye conditions that lead to damage to the optic nerve, the nerve that carries visual information from the eye to the brain.


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. Also known as farsightedness.


iFS Laser: laser technology that is a 100% blade-free approach to performing LASIK.
Intacs®: a reversible refractive surgery procedure that can be used to correct mild amounts of nearsightedness.
Intraocular lens: also known as IOLs are lenses implanted in the eye, usually replacing the existing crystalline lens because it has been clouded over by a cataract.
Intraocular pressure: the fluid pressure inside the eye.
Iris: the colored ring of tissue suspended behind the cornea and immediately in front of the lens.


Keratectomy: the surgical removal of corneal tissue.
Keratotomy: a surgical incision of the cornea.
Keratitis: inflammation of the cornea.
Keratomileusis: lifting the front surface of the cornea in order to reshape it.


Laser: the acronym for light amplification by stimulated emission of radiation. A laser is an instrument that produces a powerful beam of light that can vaporize tissue.
LASIK: the acronym for “laser assisted in situ keratomileuses” which refers to creating a flap in the cornea with a microkeratome and using a laser to reshape the underlying cornea. LASIK is the world's most common laser corrective surgery.
Lens: a part of the eye that provides focusing power. The lens is able to change shape allowing the eye to focus at different distances.


Microkeratome: a mechanical surgical device that is affixed to the eye by use of a vacuum ring. When secured, a very sharp blade cuts a layer of the cornea at a predetermined depth.
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. Also known as nearsightedness.


Nearsightedness: the common term for myopia.
NearVision SM CK®: unique conductive keratoplasty vision correction treatment that reshapes the cornea using radiofrequency.


Ophthalmologist: a medical doctor specializing in the diagnosis and medical or surgical treatment of visual disorders and eye diseases.
Optician: an expert in the art and science of making and fitting glasses and may also dispense contact lenses.
Optomap™: a retinal exam that provides a panoramic view of the back of a person’s eye.
Optometrist: a primary eye care provider who diagnoses, manages, and treats disorders of the visual system and eye diseases.


Potential acuity meter: also known as PAM, a device that is designed to project an eye chart directly onto the retina, allowing the examiner to test visual acuity without the interference of the cloudy lens.
PRK: the acronym for “photorefractive keratectomy” which is a procedure involving the removal of the surface layer of the cornea and the use of a computer-controlled excimer laser to reshape the stroma.
Presbyopia: the inability to maintain a clear image as objects are moved closer. Presbyopia is due to reduced elasticity of the lens with increasing age.
Pterygium: a pterygium is the growth of abnormal tissue, which tends to extend from the corner of the eye near the center of the eye. In appearance, pterygium is typically pink and fleshy and is located on the white part of the eye.
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.


Radial Keratotomy: commonly referred to as RK; a surgical procedure designed to correct myopia (nearsightedness) by flattening the cornea using radial cuts.
Refraction: a test to determine the refractive power of the eye; also, the bending of light as it passes from one medium into another.
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.
Rezoom™ Multifocal IOL: an advanced procedure used to treat cataracts and helps most people see without depending on glasses.


Sclera: the tough, white, outer layer of the eye that, along with the cornea, protects the eyeball.
Selective laser trabeculoplasty: also known as SLT, is one of newest advances in the surgical treatment of intraocular pressure in patients with open-angle glaucoma.
Stroma: the middle and thickest layer of tissue in the cornea.


Visual Acuity: the clearness of vision; the ability to distinguish details and shapes.
VISX Star S4 ActiveTrak™: Excimer Laser System that incorporates variable beam technology with an active eye tracking system.
Vitreous Humor: the transparent, colorless mass of gel that lies behind the lens and in front of the retina and fills the globe of the eyeball.


Wavefront: a measure of the total refractive errors of the eye, including nearsightedness, farsightedness, astigmatism, and other refractive errors that cannot be corrected with glasses or contacts