Common LASIK Terms

Here is a listing of common LASIK terms, defined, for when you are researching a laser eye surgery procedure:


The capacity of the eye to see fine detail.

Affiliated TLC Doctors

Eye doctors who are part of TLC’s large network of affiliated optometrist and are trained to manage patients before and after laser vision correction. These doctors collaborate with the surgeons at TLC Laser Eye Centers to determine your candidacy for LASIK. Nearly one out of every four practicing optometrists in North America have affiliated themselves with TLC.


A drug that provides a loss of feeling or numbness in a certain area of the body.

Anesthetic Drops

Numbing drops that are placed on the eye prior to LASIK to help minimize any discomfort during the procedure.


Astigmatism is a term used to describe an eye that is not perfectly round.  An astigmatic eye is one that has a more complex shape (think about the difference in shape between a ping pong ball and an egg). Astigmatic corneas focus light in two different places in the eye, making both near and distance vision difficult.  Our TLC LASIK blog can answer more of your questions about astigmatism and LASIK.

Best corrected visual acuity (BCVA)

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

Bilateral LASIK

LASIK surgery that is performed on both eyes.

Bladeless LASIK

A type of LASIK in which the surgeon uses the IntraLase laser to create the protective corneal flap. In both the LASIK and Custom LASIK procedures, a flap of corneal tissue is created and then folded back. The bladeless LASIK technology allows surgeons to safely create a uniform corneal flap for every patient, without the use of any blades.


The transparent portion of the eyeball that aids in focusing light onto the retina at the back of the eye.  This is the part of the eye that is reshaped with laser vision correction surgery such as LASIK. The cornea is composed of five layers of tissue.

Corneal Epithelium

Soft surface tissue that covers the front of the cornea.

Corneal Flap

The first step in the LASIK procedure involves creating and manipulating a protective flap on the cornea.

Custom LASIK

A procedure that allows your surgeon to customize the LASIK procedure to your individual eyes. Custom LASIK uses an instrument called a wavefront analyzer to measure the way light travels through your eye. The wavefront analyzer creates a detailed map of your eye’s unique visual properties. This data is then used to program the excimer laser to customize your treatment.


A unit of measurement used to describe the light bending properties of an optical system.  Glasses that correct for nearsightedness are expressed as negative (-) numbers and positive (+) for farsightedness.

Dry Eyes

A deficiency in the production of tears. Patients typically describe dryness as burning, irritation or a foreign body sensation in their eyes.

Excimer Laser

A laser used for vision correction that uses ultraviolet light to reshape the cornea.

Farsightedness (Hyperopia)

Hyperopia, or farsightedness is a refractive error in which the eye is too short to focus light properly onto the retina.

Flexible Spending Account (FSA)

An employer-provided health savings account (available in the United States only). This account allows for specific tax advantages when setting aside funds for qualified FSA expenditure such as LASIK.

Health Savings Account (HSA)

A health savings account is an account created for people who are currently covered under a high deductible health plan (HDHP). Not to be confused with an FSA, this account allows individuals to save for medical expenses that HDHP’s do not cover. The contributions to this account are made by the individual and/or their employer, and are limited to a certain yearly amount. Like a FSA, there can be certain tax advantages to using a health savings account to pay for LASIK. Learn more about the differences between HSAs and FSAs on the TLC LASIK blog.

Higher-Order Aberrations

Imperfections in the visual system that cause decreased night vision, glare and halos. Higher-order aberrations do not always affect vision.

Health Reimbursement Account (HRA)

An employer-funded plan that will reimburse employees for out-of-pocket medical expenses not covered by the company’s standard insurance plan. Reimbursement dollars received by the employee are generally tax free.


The colored portion of your eye that expands and contracts to allow more or less light into your eye.


A process in which tissue is removed to change the corneal shape.  In LASIK, laser energy is used to reshape the cornea.


Also known as Laser-In-Situ Keratomileusis, LASIK is the most frequently performed elective health care procedure in North America. It is a highly effective outpatient procedure that is suitable for most prescriptions. In LASIK, a protective corneal flap is created and gently lifted by the surgeon. A computer-controlled cool beam of light from an excimer laser is used to gently reshape the front surface (cornea) of your eye.  The corneal flap is then repositioned to allow for minimal discomfort and quick visual recovery.

LASIK Candidate

A patient who meets a series of criteria that make him or her an ideal candidate for the LASIK procedure.

LASIK Consultation

A thorough eye examination and discussion that is used to determine if a person is a good candidate for LASIK laser vision correction surgery. During a LASIK consultation, the patient meets with a doctor to have a comprehensive eye exam and discuss the various surgical correction options available. At the consultation, the doctor will also describe which LASIK procedure s/he believes will yield the best post-operative visual results.


A clear structure located behind the iris. Its primary function is to allow the eye to focus on objects at distance (when it is relaxed), and up close (when it contracts).

Lid Speculum

An instrument used in LASIK surgery that gently holds the patient’s eyelids apart, eliminating the possibility of blinking.

Lower-Order Aberrations

Also called refractive errors.  These include myopia, hyperopia and astigmatism.


A surgical instrument that uses a blade to make the corneal flap at the beginning of a LASIK procedure. (As its name implies, bladeless LASIK does not use a bladed microkeratome.)


A compromise between far and near vision in which one eye is fully corrected for distance and the other eye is corrected for seeing up close.  Patients who have a monovision correction with contact lenses or LASIK will not see as well far away as someone who has a full distance vision correction.

Nearsightedness (Myopia)

Myopia, or nearsightedness is a refractive error in which you see better close up than you do at a distance. Myopia is caused by an eyeball that is either too long or the cornea is too steep to focus light properly onto the retina.

Night Glare (Halos)

Occurs when a person sees a halo or starburst shape around lights at night. This can be one of the negative side effects of laser vision correction.

Off-label Use

A practice in which physicians prescribe approved medications and/or procedures for a use other than its intended indications. In the United States, the regulations of the Food and Drug Administration (FDA) permit physicians to prescribe off-label.


A medical doctor specializing in the diagnosis and treatment of eye diseases. This is considered both a surgical and medical profession.


A specialist who sells vision correction lenses and performs necessary adjustments.


A primary medical professional who is trained and licensed to diagnose and treat the eyes for visual defects, ocular disease and other impairments.  In addition to prescribing corrective lenses in the form of glasses and contacts, an optometrist can monitor and treat a variety of ocular diseases that are nonsurgical in nature. Optometrists are an important part of the TLC care team.


A potential side effect of laser vision correction that happens when the eye over responds to the laser treatment. Your eyes can heal in ways that the surgeon cannot anticipate. In the case of over-correction, the final prescription is more than what the surgeon had originally intended.


Presbyopia is a condition that becomes more common as people reach their 40s and 50s. As the human body ages, the lens inside the eye loses its elasticity, making it more difficult to read smaller print. Because laser vision correction such as LASIK does not deal with the lens of your eye, it cannot correct this problem.  Consult the TLC LASIK blog for more information about your options regarding presbyopia.


Describes the healing period after your LASIK procedure. Patients should carefully adhere to certain requirements during this period for a healthy and successful LASIK recovery.

PRK (Photorefractive Keratectomy)

Prior to LASIK, this was the most common laser vision correction procedure. For the PRK eye surgery procedure, the surgeon begins by removing the eye’s protective first layer of cells, or epithelium, to reveal the next layer of corneal tissue. The surgeon then applies computer-controlled pulses of cool light from an excimer laser to reshape the curvature of the eye. PRK patients require about five days for the epithelium to heal and allow clearer vision. Learn more about PRK at our TLC LASIK blog.


The hole in the center of your iris (the colored part of 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 iris constricts, causing the pupil to become smaller so less light can pass through. When it is dark, the pupil expands to allow more light to reach the back of your eye.


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 to the brain.

TLC Surgeon or TLC LASIK Surgeon

Ophthalmic surgeons who perform LASIK and other vision correction procedures at TLC’s LASIK centers.  TLC works with highly trained, experienced and skilled laser eye surgeons. These surgeons maintain professional independence and exercise independent medical judgment.  They are not employed by TLC and TLC does not in any way control their medical decisions.

Uncorrected visual acuity (UCVA)

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

Visual Acuity

Sharpness or clearness of vision. Visual acuity is measured by the ability to discern letters or numbers at a given distance, according to a fixed standard.

Wavefront Analyzer

A specialized technology designed to create a 3-D map of the eye’s visual system. Originally developed for use in high-powered space telescopes, the wavefront analyzer is now adapted for eye care. A single beam of infrared light is passed into the eye and focused on the retina. The light is then reflected off the retina, back through the eye and passed through a lenslet array to a sensor. In the process, 240 different points are measured and analyzed to create a map of your eye’s light bending characteristics – think of it as an individualized fingerprint of your vision. This technology uncovers unique characteristics of the eye that are not able to be measured using standard examination methods.