LASIK Terminology


The capacity of the eye to see fine detail.


Astigmatism is blurry vision produced by football-shaped cornea that is too steep in one place and too flat in another. Astigmatic corneas focus light in two different places in the eye, making both near and distance vision a problem.

Best corrected visual acuity (BCVA)

The best possible vision a person can achieve with corrective lenses measured in terms of Snellen lines on an eye chart.

Bilateral LASIK

Surgery performed on both eyes.

Bladeless LASIK

In the LASIK and Custom LASIK procedures, a flap of corneal tissue must be created and then folded back. With Bladeless LASIK, the surgeon uses the IntraLase laser to create the corneal flap. This technology enables the surgeon the ability to customize the corneal flap for every individual patient.


When the natural lens if eye begins to cloud creating a cloudy spot or visual impairment in your vision. Usually caused by age or other risk factors.


The cornea is sometimes referred to as the ‘window of the eye.’ It provides most of the focusing power when light enters the eye. The cornea is composed of five layers of tissue. This is the part of the eye reshaped by laser vision correction.

Corneal Epithelium

This is epithelial tissue and it covers the front of the cornea and acts as the barrier to help protect the cornea, resisting the flow of fluids from the tears, to prevent bacteria from entering the epithelium and corneal stroma.

Custom LASIK

Custom LASIK is a procedure that enables your surgeon to further customize the conventional LASIK procedure to your individual eyes. CustomLASIK uses a tool called a wavefront analyzer to measure the way light travels through your eye. The wavefront analyzer creates a 3-D map of your eye, this data is then programmed into the laser to customize your treatment.


A measurement of the optical power (whole numbers) of your prescription in a + or – format. Myopic would be considered a – measurement and hyperopic would be considered a + measurement.

Excimer Laser

A laser using cool beams of ultraviolet light, used to perform LASIK procedures.

Farsightedness (Hyperopia)

A refractive error in which you see better from a distance than close up. Hyperopia is caused by an eyeball that is too short to focus light on the retina.

Higher-Order Aberrations

Irregularities, other than refractive errors, that can cause such problems as decreased contrast sensitivity or night vision, glare and halos. Higher-order aberrations do not always affect vision.

IOL (Intraocular Lens Implant)

Implanted lens used to replace the crystalline lens of the eye due to cataract clouding or as a form of refractive vision correction.


Is the thin, circular portion of you eye that creates the color (green, brown, blue). It controls the size of your pupil allowing certain amounts of light to reach the retina to focus.


To remove the corneal tissue, this is done to complete the LASIK procedure.


LASIK (Laser-In-Situ Keratomileusis) is currently one of the most frequently performed elective procedures inNorth America. It is a highly effective outpatient procedure that is suitable for low, moderate and higher prescriptions. In LASIK, a protective hinged flap is created and gently lifted by the surgeon. Then, a computer controlled cool beam of light from the excimer laser is used to gently reshape the front surface (cornea) of your eye.


The lens is the clear structure located behind the pupil. Its primary function is to provide fine-tuning for focusing and reading, which it accomplishes by altering its shape.

Lid Speculum

An instrument, placed in the eye before surgery, to gently hold the lids apart, eliminating possibility of blinking.

Lower-Order Aberrations

Also called refractive errors; includes myopia, hyperopia and astigmatism.


The blade which is used to make the corneal flaps during the beginning stages of a LASIK procedure.


When, with vision correction, one eye is intentionally left slightly nearsighted. This allows you to maintain your ability to read after presbyopia begins. Gaining this near vision means giving up some distance sharpness.

Nearsightedness (Myopia)

A refractive error in which you see better close up than from a distance. Myopia is caused by an eyeball that is too long to focus light on the retina or a cornea which is too steeply curved.


The anatomy, physiology and study of eye diseases. These are considered both surgical and medical professionals.


Makes vision correction lenses and performs necessary adjustments,


The visual system and information processing profession. Able to diagnose certain diseases and help regulate sight by lens prescription. Considered a medical and non surgical professional.


Presbyopia develops as the lens of the eye loses some of the flexibility that characterizes a younger eye. Everyone experiences the effects of presbyopia, typically between the ages of 40 and 50.

PRK (Photorefractive Keratectomy)

Prior to LASIK, PRK was the most common laser vision correction procedure. For the PRK procedure, the surgeon first removes the eye’s protective first layer of cells, or epithelium, to reveal the next layer of corneal tissue. The surgeon will apply computer-controlled pulses of cool light from the excimer laser to reshape the curvature of the eye. PRK patients require about three days for the epithelium to heal and allow clearer vision.


The pupil is the “black circle” in your eye. The primary function of the pupil is to control the amount of light entering your eye. When you are in a bright environment, the pupil becomes smaller to allow less light to pass through. When it is dark, the pupil expands to allow more light to reach the back of your eye.


The retina consists of fine nerve tissue that lines the inside wall of the eye and acts like the film in a camera. Its primary function is to capture and transmit images.

Uncorrected visual acuity (UCVA)

The best possible vision a person can achieve without corrective lenses measured in terms of Snellen lines on an eye chart.

Wavefront Analyzer

Originally developed for use in high-powered telescopes to reduce distortions in space, now adapted for eyecare. A single beam of infrared laser light is passed into the eye and focused on the retina. The light is then reflected off the retina, passed back through the eye, through a lenslet array to a sensor, and then analyzed from 200 different aspects to create a map of the eye – or fingerprint of vision. This technology uncovers unique characteristics of the eye never measured before using standard methods for glasses and contact lenses.

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