TRSC Femtosecond LASIK - Carl Ziess VisuMax Femtosecond Laser

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Frequently Asked Questions about Femtosecond LASIK

How is a femtosecond laser used in the LASIK procedure??

To help you understand the use and purpose of the femtosecond laser, here is a general overview of the entire LASIK procedure. LASIK is a type of refractive surgery in which the outermost structure of the eye, the cornea, is reshaped in order to correct the patient’s refractive error. The LASIK procedure does not involve penetration of the eye, and is not considered an intraocular procedure.

There are 3 main steps in the LASIK procedure:

1. Creation of the corneal flap

The laser treatment must be made in the middle layer of the cornea, the stroma, in order for the correction to be permanent. A flap is created in the cornea, by slicing a superficial layer consisting of approximately 1/3 the corneal thickness, allowing the surgeon access to the stroma. The flap is not cut 360 degrees around the cornea, and is left with a retained hinge. This step can be done with either a conventional microkeratome blade or a femtosecond laser.

2. Reshaping of the stroma

The corneal flap is lifted and folded back at the hinge, and then the excimer laser is applied to the now-exposed stroma. A cool beam excimer laser is used to reshape the stroma to correct the patient’s refractive error. At TRSC, we have two choices of lasers for this step: either a conventional excimer laser (Bausch & Lomb Technolas z217), or a more customized excimer laser (Carl Zeiss MEL 80) with wavefront correction capabilities.

3. Repositioning of the flap

After the excimer laser has reshaped the cornea, the surgeon will place the corneal flap back down and smooth it out, making sure there are no wrinkles. The flap will act as a natural bandage, allowing fast healing and added comfort for the patient.

What is the advantage of using a femtosecond laser over a microkeratome blade to create the corneal flap in LASIK?

Femtosecond lasers are not necessary for all LASIK patients, however there is a definite advantage for a certain subset of patients. Using a bladeless or all-laser procedure can also give peace of mind for some patients who are nervous about the use of a blade in the procedure. Computer software uses an algorithm based on the patient’s eye measurements to guide the femtosecond laser in creating the corneal flap. This allows for a more precise, reliable, and customized flap. Since the corneal flap created by a femtosecond laser (femtosecond flap) allows for a higher degree of precision, a thinner flap can be made. This means that patients who previously were not candidates for LASIK may now be able to undergo the procedure safely. Also, since penetration of the cornea is not as deep, there is a smaller risk of postoperative dry eye. However, a precisely cut computer-guided flap can have more advantages than just thickness. It also means a more perfectly centered flap, which can reduce chances of postoperative visual symptoms such as glare and halos, and is especially useful for patients with abnormally large pupils. A femtosecond flap can also be customized for hinge size, flap edge angles, and overall shape. The edges of a femtosecond flap will be slightly thicker and not have a knife-edge like microkeratome flaps, which are thinner and more prone to tearing during the surgery. Although flap complications are still possible with femtosecond flaps, they occur more rarely than with microkeratomes. Flap complications can include buttonhole flaps, incomplete flaps, free caps, and decentered flaps. Also, since there is no physical blade used to create the flap, it means that tear film and debris will not be dragged under the flap and create postoperative problems such as infection or contamination which can lead to diffuse lamellar keratitis. In certain eyes that suffer from high degrees of higher order aberrations, visual quality is often improved with femtosecond LASIK.

While there are many advantages to using a femtosecond laser for creation of the flap, microkeratomes are still commonly used in the LASIK procedure. Microkeratomes have been used since the inception of the LASIK procedure, and continue to be the most popular method of flap creation in the LASIK procedure today. Most patients have enough corneal thickness that such ultra-precision with the femtosecond laser is not necessary. Also, although the mechanism is not yet fully understood, there have been reports of mildly increased photophobia (light sensitivity) and halo effects postoperatively with the femtosecond laser.

At your preoperative examination, the surgeon will look at all of your eye measurements and recommend which procedure is best for you.

Advantages of the Femtosecond Laser

increased comfort for patients who are afraid of the use of a blade
more precise and reliable corneal flap which can be advantageous for patients with:

thinner corneas
dry eyes
abnormally large pupils

flap features can be customized:

hinge size
flap edge angles
overall shape to match the cornea

lower incidence of flap complications
tear film and debris will not be dragged under the flap
better visual quality (for eyes with high degrees of higher order aberrations)

Advantages of the Microkeratome

cheaper
okay for most patients (this is still the most commonly used method for flap creation internationally)

Is femtosecond LASIK the same as wavefront LASIK?

No, these are referring to two different steps in the LASIK procedure. A femtosecond laser is used in the first step of LASIK, to create the corneal flap. A femtosecond laser can be used instead of a microkeratome blade. In the second step of the LASIK procedure, an excimer laser is used to reshape the cornea. This excimer laser can either be a conventional excimer laser or it can incorporate wavefront technology. Wavefront lasers allow a more customized treatment and are especially helpful in reducing higher order aberrations which cause visual side effects such as glare and halos. It is possible to have femtosecond LASIK with or without a wavefront laser, and it is also possible to have wavefront LASIK with either a microkeratome or a femtosecond laser. At TRSC, all patients who choose FemtoLASIK will have wavefront correction by the excimer laser.