Term

Definition

Aberrations

Imperfections, irregularities and/or distortions of the optical quality of the eye that cause unclear vision

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

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Best Corrected Visual Acuity 20/20

Noted as BCVA; The best possible vision that an eye can achieve with the use of glasses or contact lenses

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

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

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

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.

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Iris

The colored portion of the eye behind the cornea

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

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

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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

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

Pupil

The black opening in the center of the iris that allows light into the eye; its size increases under dim lighting

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

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

Snellen Chart

The eye chart commonly used to measure visual acuity, where good vision is 20/20

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

Wavefront Sensing

A computerized technology that analyzes all the eye’s higher order aberrations as well as nearsightedness, farsightedness and astigmatism