LASIK Glossary

Ablation: in eye surgery, it is the removal of eye tissue to correct a refractive error.

Astigmatism: a condition of visual distortion caused by an improperly shaped cornea resulting in blurred vision.

Cornea: the clear outer layer of the eye that covers the iris and pupil, lets light into the eye, and provides most of the focusing power of the eye.

Corneal Epithelium: thin layer of cells comprising the outermost surface of the cornea kept moist by tears.

Corneal Stroma: thick, transparent middle layer of the cornea that performs most of the focusing for the eye.

Excimer Laser: a form of ultraviolet chemical laser that is exceptionally well focused and capable of very delicate control.

Flap & Zap: a slang term for LASIK.

Higher Order Aberrations (HOA): complex vision errors causing difficulty seeing at night, glare, halos, blurring, starburst patterns, or double vision.

Hyperopia: also called farsightedness, a condition in which vision is better for distant objects than for near objects.

Iris: the colored part of the eye, located behind the cornea and in front of the lens. The tiny muscles inside the iris that play a part in regulating the amount of light that enters the eye by either dilating (widening) or contracting (narrowing) the size of the pupil.

Lens: a clear structure in the eye located between the iris and vitreous humour which focuses light rays on the retina, allows the eye to focus at different distances.

Microkeratome: a surgical device that creates a corneal flap. It attaches to the eye with a vacuum ring and then a very sharp blade cuts a layer of the cornea at a predetermined depth.

Monovision: correcting vision in one eye for near vision and the other eye for distance vision.

Myopia: also called nearsightedness, a condition in which close-up vision may be clear but distance vision is blurry.

Presbyopia: a condition due to the reduced elasticity of the eye that occurs with age and results in the inability to maintain focus on close-up objects.

Pupil: the opening of the eye in the center of the iris that changes in size according to the amount of light present.

Refractive Error: a condition where light entering the eye is not clearly focused on the retina, resulting in astigmatism, hyperopia, and myopia.

Retina: layer of nerve tissue in the back of the eye that is sensitive to light, converts and transmits images from the eye to the brain.

Visual Acuity: the clearness and crispness of vision.

Vitreous Humor: the clear gel that fills the center of the eyeball, located behind the lens and in front of the retina.

Wavefront: a complete measurement of the eye's refractive errors, including farsightedness, nearsightedness, astigmatism, and other refractive errors that are not correctable with glasses or contacts.