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Glossary of Terms

Term Definition
Aberrations Imperfections, irregularities, and/or distortions of the optical quality of the eye that cause unclear vision
Ablation Removal of tissue as is done with the excimer laser during refractive surgery
Ablation Zone The area of tissue removed during refractive surgery; needs to approximate the pupil size to avoid post-op glare and halos
Accommodation The ability of the lens inside the eye to change focus from distance to near range; begins to decrease in our 40s requiring the use of reading glasses
Astigmatism A refractive error caused by an uneven power of the cornea; light entering the eye comes to two points of focus rather than one; has an amount and an orientation
Axis The orientation of an astigmatic correction
Best Corrected Visual Acuity (BCVA) Noted as BCVA; The best possible vision that an eye can achieve with the use of glasses or contact lenses
Broad Beam Laser An excimer laser with a large treatment beam diameter (6mm to 8mm) that can be used to ablate the cornea
Cataract An age-normal loss of clarity of the natural lens inside of the human eye. Typically develops later in life and can reduce vision due to the inability of light to enter the eye.
Contrast Sensitivity The ability to detect subtle differences between details that are not black on white such as shades of gray; important in determining the quality of vision after refractive surgery
Cornea The clear dome of tissue at the front of the eye that is the first element of the focusing system; provides two-thirds of the eye’s focusing power
Corneal Topography A computer-derived, color-coded representation of the architecture and shape of the cornea; a map of your eye
Customized Ablation The use of wavefront sensing technology and a flying spot excimer laser to treat all of the lower and higher order aberrations of the human eye
Cylinder The amount of lens power necessary to compensate for astigmatism
Diopter Unit of measurement for the power of a lens or of refractive error
Dry Eye A condition of the eye in which adequate tears are not being produced to keep the surface of the eye moist and lubricated
Emmetropia A condition in which there is no measurable refractive error; a near perfect focus of the eye
Enhancement A repeat of a refractive surgical procedure in an attempt to improve vision without glasses
Epithelium Top surface layer of the cornea; 6 - 7 cells thick
Excimer Laser The ultraviolet laser used to remove corneal tissue during refractive surgery
Eye Tracker The device used by the excimer laser’s computer that allows it to adjust the treatment beam to compensate for small movements of the eye
Femtosecond Laser A precise laser used to make a flap in the cornea prior to the excimer laser treatment during LASIK
Flying Spot Laser The latest generation excimer laser that uses a small (1mm - 2mm) diameter treatment beam to very precisely re-sculpt the cornea
Glare A complication of refractive surgery that causes points of light of look brighter and less distinct
Halos A complication of refractive surgery that causes a point of light to appear to have rings of light around it
Haze A complication of PRK in which the epithelium of the cornea does not heal with perfect clarity
Higher Order Aberrations Subtle imperfection of the optics of the eye above and beyond nearsightedness, farsightedness and astigmatism; not corrected with glasses or contact lenses
Hyperopia or Farsightedness A refractive error in which the optics of the eye are not strong enough for the front to back length of the eye and the light is focused behind the retina; objects at a distance focus better than objects up close
Inflammation Human tissue’s natural reaction to trauma; often accompanied by discomfort, redness and swelling
INTACS Intrastromal corneal rings; a non-laser refractive surgical option for low degrees of nearsightedness
Implant, Aphakic A small artificial lens placed into the eye to restore the eye's focus after cataract surgery to remove a cloudy natural lens
Implant, Phakic A small artificial lens placed into the eye along with the eye's natural lens to reduce significant amounts of refractive error such as myopia
Iris The colored portion of the eye behind the cornea
Keratomileusis Re-sculpting of the shape of the cornea to change its focusing power; refractive surgery
LASEK Laser Epithelial Keratomileusis; a variation of refractive surgery in which the corneal epithelium is slid back prior to laser treatment and then repositioned after the treatment
LASIK Laser In-Situ Keratomileusis; the refractive surgical procedure where a flap of tissue is created in the cornea, lifted allowing the excimer laser to re-shape the cornea to correct refractive errors and then repositioned where it naturally re-adheres
Lens The part of the eye behind the iris that adjusts focus for different distances by changing shape
Macula The central portion of the retina responsible for high detail, color vision
Microkeratome A very precise surgical device used to create the corneal flap during the LASIK procedure
Micron The precise unit of measurement used in refractive surgery; equal to 1/1000th of a millimeter or one millionth of an inch
Monovision The intentional adjustment of vision in one eye for near clarity and the other for distance clarity during refractive surgery or when prescribing contact lenses
Myopia or Nearsightedness A refractive error in which the optics of the eye are too strong for the front to back length of the eye; objects up close focus better than those at a distance
Nomogram The adjustments made to diagnostic data in the process of creating a treatment profile for use with laser vision correction
Optic Nerve The bundle of 1 million nerves that transmits information from the retina (back of the eye) to the visual center of the brain
Overcorrection A situation in which the change in refractive error following refractive surgery is greater than the intended treatment
Pachymetry A precise technique for measuring the exact thickness of the cornea
Plano The term for zero refractive power. No lens is necessary to improve the focus of light into the eye.
Presbyopia The normal aging process of the human lens which causes a loss in flexibility resulting in the inability to focus on near range objects
PRK Photorefractive Keratectomy; a type of refractive surgery in which the epithelium of the cornea is removed prior to laser treatment and then allowed to naturally regrow
Pupil The black opening in the center of the iris that allows light into the eye; its size increases under dim lighting
RK Radial Keratotomy; an early version of refractive surgery for myopia that involved making spoke-like cuts in the peripheral cornea
Refraction The test used to determine the amount of nearsightedness, farsightedness and/or astigmatism
Refractive Error Any condition in which light entering the eye is not focused precisely on the retina
Regression A loss of refractive surgical effect in the time period following treatment
Retina The light sensitive, back part of the eye containing the rods and cones that turns light waves into brain waves allowing us to see
Rochester Nomogram A specialized method of analyzing the wavefront sensing data for a patient's eye during the creation of a laser vision correction treatment plan. Created by, and unique to, Flaum Eye Institute Refractive Surgery Center.
Snellen Chart The eye chart commonly used to measure visual acuity, where good vision is 20/20
Sphere The amount of lens power needed to compensate for nearsightedness or farsightedness
Stroma The central substance of the cornea that is treated with the excimer laser during refractive surgery
Tear Film The thin layer of lubricants and nutrients that covers the front surface of the cornea
Uncorrected Visual Acuity Noted as UCVA; The best possible vision that an eye can achieve without the use of glasses or contact lenses
Undercorrection A situation in which the change in refractive error following refractive surgery is less than necessary
Verisyse™ A tiny lens implant placed into the eye, without removing the eye's natural lens, to reduce the impact of very high degrees of myopia
Wavefront Sensing A computerized technology that analyzes all the eye’s higher order aberrations as well as nearsightedness, farsightedness and astigmatism