How LASIK Works


Improved Vision through Corneal Reshaping

Over 14 million Americans have had LASIK Eye Surgery since the technique was approved by the FDA in the 1990s. LASIK tackles the problems of nearsightedness, farsightedness, and astigmatism at the source – by correcting irregularities in the eye’s cornea (the “refractive error”) that is causing poor vision.Eye Doctor Performing LASIK Eye Surgery

What Is Refractive Error?

In normal vision, the cornea refracts or bends light so images are focused properly on the retina. When the cornea is misshaped, there will be errors in the cornea’s refractive power resulting in blurred or distorted images being received by the retina. Refractive error varies from person to person and this variation is the reason your glasses or contacts don’t “work” for your friends or relatives.

3 Steps in LASIK (Correct Refractive Errors)

  1. The first step of a LASIK procedure is the creation of the corneal flap, a thin segment of the outer layer of the cornea. In the early days of LASIK, an oscillating hand-held blade called a microkeratome was used to create the corneal flap; however, this technique has been superseded by all-laser or bladeless LASIK. With all-laser LASIK this step is performed with a special computer-controlled laser, the IntraLase™, which creates a thinner, more precise and more stable flap.
  2. Next, the flap is lifted and an excimer laser such as the VISX™ is used to reshape the underlying corneal tissue to correct any irregularities. This step in Custom LASIK is based on an individual 3-dimensional map of the optics of your eye, which is then programmed into the laser so that the exact amount of corneal tissue is removed to yield the best vision possible.
  3. Finally, the flap is folded back into place, where it bonds quickly.

LASIK Eye Surgery Procedure

The Steps of LASIK

Healing is rapid with all-laser LASIK, and most people can return to work the very next day. LASIK takes only minutes per eye. You can expect to feel little to no pain and perhaps just the slightest sensation of pressure. Inserting or removing contact lenses or just rubbing eyes tired from wearing glasses can produce more discomfort than a LASIK procedure.

Your Path to Visual Freedom with LASIK graphic

Key Questions About the Technology Behind the 3 Steps

What is all-laser or blade-free LASIK?

All-laser LASIK is the most advanced evolution for the flap-creation step. In the “bladeless” or “all-laser” technique, a laser forms a series of bubbles in the corneal tissue to create the flap, rather than using a blade. The advantages with this advanced technique include more accuracy, stability and greater patient comfort.

Which technology solves night vision problems?

Many of us suffer from night vision problems with or without refractive surgery. In the earliest days of laser vision correction, some patients reported halos and “starbursts” after their procedures, especially when driving at night. Patients with large pupils were susceptible to this complication.

Today’s advanced lasers have dealt authoritatively with night vision issues. In fact, many of Dr. Leavitt’s patients report improved night vision after the procedure.

How long does LASIK last?

The refractive errors corrected by LASIK stay corrected for the rest of your life. Since the cornea is living tissue there can be minor fluctuations and occasionally the need for enhancements as the cornea adapts following the procedure. These are a normal part of the post-operative process.

After the post-operative processes are complete, you can expect your vision to improve and stabilize, with many LASIK patients reporting excellent vision following the procedure that gets even better in the next months and years.

Your eyes age as you do, and for most of us who’ve reached 40, another element of the eye will cause vision trouble. The eye’s lens will gradually lose flexibility and result in a condition called presbyopia, or the need for reading glasses. Monovision LASIK can help this condition significantly.

By the time you are in your 70s, you may experience another set of age-related vision problems which LASIK doesn’t address. However, depending on the age at which you have your procedure, you may have decades of excellent vision free of the effects of refractive error.

What Can LASIK Correct?

LASIK solves poor vision at the source, correcting these common vision problems:

Myopia (nearsightedness)

Myopia DiagramNearsighted individuals have problems seeing well at a distance and are forced to wear glasses or contact lenses. The nearsighted eye is usually longer than a normal eye, and its cornea steeper, so when light passes through the cornea it is focused in front of the retina, not on the retina. This makes distant images appear blurred.

LASIK solves myopia by correcting the corneal irregularities that cause it.

Hyperopia (farsightedness)

Hyperopia DiagramFarsighted individuals have trouble reading up close or seeing objects near at hand. The farsighted eye is slightly shorter than a normal eye and has a flatter cornea, so distant objects focus behind the retina.

LASIK eliminates the causes of farsightedness.


Astigmatism DiagramUneven steepening of the cornea causes images to be focused irregularly on the retina, causing blurred vision. Astigmatism is very common and can accompany any other form of refractive error, such as myopia or hyperopia.

LASIK effectively solves Astigmatism.


Presbyopia DiagramPresbyopia is a condition that becomes noticeable for most people after the age of 45. In children and young adults, the lens inside the eye can easily focus on distant and near objects. With age, the lens stiffens and loses its ability to focus properly, especially up close, increasing the need for reading glasses and bifocals.

A LASIK technique called LASIK Monovision can resolve presbyopia by correcting one eye for near vision and the other eye for far vision. Remarkably, the brain can usually adapt. Your doctor will explain LASIK Monovision more fully at your Free Consultation.

 Understanding your Prescription

The four main vision focusing disorders of the eye are:

  • myopia (nearsightedness)
  • astigmatism (ovalness of the eye)
  • hyperopia (farsightedness) and
  • presbyopia (inability to change the focus from far to near)

The units used to represent the amount of correction needed in order to normalize vision for distance are called ‘diopters’. The more nearsighted or farsighted you are, the higher your prescription is in diopters.

Your prescription is usually written in three numbers. The following example represents a typical prescription:

OD -4.25 -1.75 X 180
OS -5.50 -1.25 X 175
+2.25 Add OU

Here is the way to decipher your prescription:

OD stands for the right eye and is the abbreviation for the Latin Ocular Dexter. OS is for the left eye. It is derived from the Latin Ocular Sinister. The 1st number (-4.25 and -5.50 in this example) is the degree of spherical nearsightedness or farsightedness. The sign identifies whether you are nearsighted (- sign) or farsighted (+ sign).

  • The second number (-1.75 and -1.25) is the degree of astigmatism. The number can be written either with a + sign or a – sign.
  • The last and 3rd number (180 and 175) is the axis or the direction of your astigmatism. An axis of 180 degrees, for example, means the astigmatism is horizontal.
  • Therefore, this prescription means that the patient is moderately nearsighted, with a moderate degree of astigmatism in a horizontal direction.
  • The “add” at the bottom of the prescription is for the reading part of a bifocal glass. It is not unusual for anyone under the age of 40 to need this.

Some people only have one number written for each eye. This is when there is no astigmatism. Schedule your free LASIK Consultation today to see if you are a good candidate for LASIK.