Thomas Eye Group Patient Education

LASIK or Laser assisted in-Situ Keratomileusis is a surgical procedure that corrects myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. LASIK combines the accuracy of the excimer laser with the quick-healing characteristics of a procedure first performed in 1949 called Lamellar Keratoplasty. The primary difference between PRK and LASIK is that the surface of the cornea is treated with PRK while the inner tissue of the cornea is treated with LASIK. Both have similar success rates, but LASIK offers patients less postoperative discomfort and a quicker return to functional vision.

Unlike PRK, LASIK preserves the top layer of cells on the eye, instead of scraping them away and waiting for them to grow back. The cornea heals more quickly and vision is restored faster, with less discomfort than PRK.

The LASIK procedure utilizes two proven surgical techniques to correct vision errors – the creation of the corneal flap and the use of the computer controlled excimer laser. During the procedure, a special device called a microkeratome (similar to a carpenter’s plane) creates a hinged flap of thin corneal tissue, and the flap is gently folded out of the way.

The second technique uses a computer controlled excimer laser with a cold, ultraviolet beam to gently sculpt the cornea, removing microscopic amounts of tissue to change the shape and allow the eye to focus more clearly. Thomas Eye Group uses only FDA approved laser technology combined with the diagnostic precision, originally invented by NASA, for use in high-powered precision telescopes, called wavefront technology. Thomas Eye Group uses the VISX STAR S4TM IR Excimer Laser System and WaveScan WaveFrontTM System. The cold laser beam then reshapes the underlying tissue, and the surgeon replaces the corneal flap over the treated area where it bonds securely, without the need for stitches.

With less surface area to heal than PRK, LASIK patients recover very quickly, and most experience little, if any, discomfort. Functional vision returns very rapidly, with the majority of patients seeing well enough to drive in a day or two without glasses or contact lenses. Most patients elect to have LASIK performed on both eyes at the same time.

Custom LASIK

Poor vision can be attributed to several types of visual imperfections, also known as lower and higher order aberrations that exist within the eye. Lower order aberrations (such as nearsightedness, farsightedness and astigmatism) have always been easily diagnosed and treated with either glasses or contact lenses or conventional LASIK treatments. Until recently, higher order aberrations, often linked to the visual glare and halos that cause night vision problems, could not be corrected and continued to affect quality of vision.

Today, however, Wavefront Mapping technology and Custom LASIK are available to examine the entire optical system for lower and higher order aberrations. The collected information is converted into a Wavefront Map. Our wavefront technology measures the way light travels through your entire optical pathway and compares it to the way light travels through an optically perfect eye. This creates a 3-D map of your vision that is as unique to you as your fingerprint, and 25 times more precise than conventional equipment. This customized “fingerprint” of your vision then transfers directly to the laser and creates a customized treatment for each individual patient. With diagnostic tools to measure 217 unique points along the optical pathway, we can detect, measure and correct each eye’s unique abnormalities.

The LASIK Procedure

The excimer laser removes microscopic layers of corneal tissue to change its shape, allowing light rays to focus more directly on the retina.

After your eye has been completely numbed using "eye drop" anesthesia, an eyelid holder will be placed between your eyelids to prevent you from blinking. Next, a surgical instrument makes a protective flap in the cornea. During this process you may feel a little pressure, but no discomfort. You will be asked to look directly at a target light while the laser reshapes the cornea, usually in less than a minute.

To treat nearsightedness, the cornea must be made flatter. This is accomplished by removing tissue from the center of the cornea.

To treat farsightedness, the central cornea must be made steeper. This is accomplished by removing tissue from around the central area.

To treat astigmatism, the cornea must be made more spherical. This is accomplished by removing more tissue from one part of the cornea than the other by changing the pattern of the beam.

Then, the protective flap is folded back in place where it bonds securely without the need for stitches. After LASIK, some patients report a slight discomfort that usually goes away within twenty-four hours.

Laser Technology

The VISX STAR S4TM IR Laser System offers variable spot beam technology – it adjusts the laser beam size according to the treatment, minimizing the removal of corneal tissue. This also allows for quicker treatment times that are typically between 10 to 40 seconds.
It also provides a larger treatment, or ablation zone. Variable Spot Scanning (VSS) technology adds a blend zone that allows treatment on the cornea to be extended to 8mm which may help reduce the risk of night vision symptoms such as glare and halos.

The VISX STAR S4TM IR Excimer Laser System uses the Active Trak 3-D Eye Tracker, a positioning device that uses infrared cameras to actively follow the tiniest motions of the eye in all three dimensions. This allows the surgeon to place the treatment on the cornea with greater precision and accuracy, despite eye movement during the procedure.

Standard laser vision correction has treated “second order” optical aberrations, or irregularities, primarily involving your cornea that are responsible for vision problems like nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. This conventional approach does not take into account the eye’s “higher order” aberrations, the imperfections of the eye that decrease the quality of your vision without necessarily decreasing your ability to see the letters of an eye chart.

At Thomas Eye Group, we can treat these problems with VISX CustomVueTM, an individualized laser vision correction procedure. Guided by the VISX WaveScanTM System, we can map the entire visual system to detect and measure all imperfections that have gone previously undetected, creating a unique fingerprint of your vision.

The resulting diagnostic information is converted to a Wavefront Map and this individualized treatment information is transferred directly to the VISX Star S4 IR laser. The Wavefront Map guides the treatment, resulting in extremely precise, individualized vision correction outcomes that would be impossible with traditional LASIK surgery, contact lenses, or eyeglasses.

Who Is a Candidate for LASIK?

Virtually everyone who wears glasses or contact lenses to see clearly is a candidate for LASIK. To be a good candidate for LASIK, the patient must be at least 18 years of age with a stable prescription of at least one year. The cornea must be of sufficient thickness to allow for the flap to be made and still have enough tissue under the flap to allow for the proper amount of tissue to be removed to achieve the targeted level of correction.
There are, however, a few exceptions. Patients with high amounts of nearsightedness, severe dry eye syndrome, very thin corneas, or other conditions, such as the beginning stages of a cataract, may be better candidates for other types of refractive surgery procedures.

Presbyopia, another type of farsightedness, occurs when the center of the eye lens hardens making it unable to accommodate near vision. This condition generally affects almost everyone around the age of 45 – even those with myopia. Eyeglasses or contact lenses may be prescribed to correct or improve the condition.

For those of you experiencing presbyopia, which creates the need for reading glasses or bifocals, blended vision is an option. Blended vision is produced using refractive surgery to have one eye remain slightly nearsighted while correcting the other for best distance vision.

Advanced Surface Ablation (ASA) is the modern version of the PRK laser vision correction procedure and is the preferred approach in certain patients. ASA utilizes the exact same high technology laser that is used with LASIK. Like LASIK, ASA can be used to treat myopia (nearsightedness), hyperopia (farsightedness) and astigmatism.

Also called LASEK or Laser Epithelial Keratomileusis, this relatively new procedure represents a surgical advancement over PRK, first approved by the FDA in 1995. It combines certain elements of both PRK and the more popular LASIK procedure and may offer some advantages over LASIK for certain patients.

ASA is most commonly chosen for patients with corneas that are too thin for LASIK, or in cases in which creating or lifting a LASIK flap carries an undesirable risk. This procedure is often preferred for patients in special requirement professions such as military, aviation, and special forces.

With LASEK, instead of removing the epithelium, as with PRK, a flap of surface epithelium is loosened with a diluted alcohol solution and moved aside. The surface under the epithelium is treated with the laser and the epithelial flap is returned to its original position, as with LASIK. A protective, soft contact lens is then placed over the cornea to make the eye more comfortable while it heals.

Using the epithelial flap as a natural protective bandage with LASEK, as opposed to completely removing the epithelium as with PRK, may improve healing. It may also reduce postoperative discomfort and the incidence of postoperative haze. Plus, the margin of safety with LASEK is increased over LASIK as the need for a microkeratome is eliminated.

It usually takes from three to five days for the epithelium to fully heal. Because the return to functional vision is longer than with LASIK, many LASEK patients prefer to have one eye treated at a time.

Although the ultimate visual results after ASA are outstanding and equivalent to LASIK, the first few weeks can be somewhat unpredictable as far as the level of vision and discomfort are concerned. For most patients, the recovery resembles LASIK quickly achieving a very useful level of vision and minimal discomfort. For others, however, the discomfort can be more prominent and a slower visual recovery can occur. For this reason, we advise that ASA patients carefully plan their postoperative period during a time that there will be minimal visual demands and occupational requirements. It is wise to delay travel until comfort and vision have reached suitable levels.

We will ask you to avoid immersion of your eyes in water for two to three weeks. This includes swimming and hot tubs. Otherwise, as your vision improves, you may resume your normal activities without major restriction.

If a person’s cornea is too thin, the degree of myopia too high, or the shape of the cornea abnormal, laser treatment of the surface of the cornea may be a better option. PRK or Photorefractive Keratectomy, was the first procedure performed using the excimer laser. It corrects vision by reshaping the surface of the cornea.

Prior to surgery, drops are instilled to numb the eye. The patient lies down on a reclining chair with a secure headrest to hold the head still. The eye to be operated on is fitted with a speculum to keep the eyelid from blinking. The epithelium, a thin layer of cells that covers the cornea, is completely removed. The process of cell removal can vary by surgeon. The most common way is by using a solution of diluted alcohol to help loosen the cells from the surface where they are manually removed by the surgeon. A light is targeted toward the eye, and the patient is asked to fixate or stare at the light, so that the laser can be directed precisely to reshape the cornea. The cool laser beam then removes a very thin layer of corneal tissue, thinner than a human hair, and reshapes the cornea to enable light to focus properly on the retina. The laser treatment time usually lasts less than one minute. Following the surgery, drops are instilled in the eye(s) to facilitate healing and to prevent infection. A special contact lens is applied that acts a bandage. The lens must be worn for at least three days, and the doctor will remove it at a follow-up visit. New epithelium then grows back over the treated area, usually in three to five days.

Refractive surgery may not always yield the desired results. In some cases, the surgery can be repeated. PRK will not eliminate the need for reading glasses.

The Recovery Process

After surgery, the patient returns home with antibiotic drops, which must be instilled directly into the eye several times a day to prevent infection. Corticosteroid drops or anti-inflammatory medication may be prescribed to alleviate swelling. Strenuous physical activity should be limited until the doctor has determined that the eye(s) has healed properly.

It takes approximately three days for the eye's surface membrane to heal. Vision improvement should be noticeable within a few days after surgery. Full recovery takes up to six weeks. During this recovery time, vision is approximately 20/40 or better. Vision improvements are gradual but should be complete within six months.

If you would like to discuss this procedure with one of our eye-surgery specialists, please call us for an appointment, or use our online appointment request form.