All Laser LASIK – Femtosecond Laser Technology – Bladeless

All-laser LASIK is an advanced form of LASIK surgery that uses two separate lasers — a femtosecond laser for the first step of the procedure (creating the corneal flap) and an excimer laser to reshape the underlying corneal tissue and improve vision.

In conventional LASIK, the corneal flap is created with a bladed instrument called a microkeratome. All-laser LASIK eliminates the need for a surgical blade and offers greater precision and control, reducing LASIK risks and complications related to flap creation.

What is a Femtosecond Laser?

A femtosecond laser is a specialized laser used for eye surgery and other medical and technical applications.

The word "femtosecond" refers to the units used to measure the duration of each pulse. One femtosecond is equal to one millionth of one billionth of a second, or one millionth of a nanosecond. (Yes, really.)

How Does a Femtosecond Laser Create a LASIK Flap?

Femtosecond lasers for LASIK direct tiny, rapid pulses of infrared light to a precise depth within the cornea. This depth is determined by the surgeon and is entered into the computer that controls the laser.

These high-energy light pulses separate corneal tissue at the molecular level by a process called photodisruption, creating microscopic bubbles of carbon dioxide and water at their point of impact. The laser moves back and forth across your eye, creating a uniform layer of these bubbles at the junction between what becomes the back surface of the corneal flap and the underlying corneal tissue (called the stromal bed).

The speed with which the femtosecond laser creates a corneal flap depends on the frequency rating of the laser. The frequency of the delivery of the laser pulses is measured in hertz (Hz), which generally define how many times an event occurs per second. Modern femtosecond lasers for LASIK have repetition rates up to 150 kilohertz (kHz) and higher, meaning they are capable of creating 150,000 laser pulses per second.

Once the flap has been created with the femtosecond laser, the surgeon manually lifts it and folds it back on a small zone of untouched tissue that serves as a hinge for the flap, keeping it attached to the eye. A different laser (called an excimer laser) is then used to reshape the eye.

Early femtosecond lasers (with repetition rates of 15 kHz to 30 kHz) required significantly more time to create a flap than a microkeratome, with some requiring 90 seconds or more. Today's modern FS lasers can create a corneal flap in less than 30 seconds.

Advantages of all-laser LASIK

Femtosecond lasers offer greater precision and control than a bladed microkeratome when creating a corneal flap. All-laser LASIK thereby reduces the risk of flap complications during LASIK surgery.

Though flap complications from the use of a bladed microkeratome are infrequent, a risk remains for undesired outcomes such as partial flaps (due to a mechanical problem with the microkeratome during flap creation), buttonhole flaps (a too-thin flap with a hole in its center) and "free caps" (a flap with no hinge to keep it attached to the eye).

These types of flap complications are virtually eliminated when a femtosecond laser is used to create the corneal flap in all-laser LASIK.

It should be noted, however, that many LASIK surgeons still prefer using a bladed microkeratome rather than a femtosecond laser for creating the corneal flap. A microkeratome can cut the flap in less time than a femtosecond laser, which can be a factor in patient comfort. And in the hands of a skilled surgeon, complications from flaps created with a microkeratome are very rare. Proponents of microkeratomes also point out that certain complications can occur from flaps created with a femtosecond laser, such as post-operative inflammation and transient light sensitivity.

Also, because a microkeratome is much less expensive than a femtosecond laser, surgeons who use a microkeratome can pass these savings along to their patients and charge less for conventional LASIK than what they would charge for all-laser LASIK.

All-Laser LASIK Preferred by Patients

Many good surgical candidates choose not to have LASIK surgery or undergo PRK, LASEK or Epi-LASIK instead of LASIK because they are fearful of a bladed instrument being used on their eyes. All-laser LASIK relieves a good deal of anxiety about LASIK surgery because no surgical blade is involved.

One study found that when given the choice, 81 percent of LASIK candidates prefer all-laser LASIK over conventional LASIK with the corneal flap cut with a bladed microkeratome.*

IntraLase: The First Femtosecond Laser for All-Laser LASIK

IntraLase Corp. in Irvine, California developed the first femtosecond (FS) laser approved for LASIK surgery performed in the United States. The first IntraLase FS laser gained FDA approval in 2001 and was introduced commercially in the U.S. later that year.

Until 2004, IntraLase was the only manufacturer who offered an FDA-approved femtosecond laser for LASIK. For this reason, all-laser LASIK was (and still is) sometimes called "IntraLase LASIK" or "IntraLASIK."

By June 30, 2005, nearly 300 IntraLase FS lasers had been installed in refractive surgery practices worldwide and approximately 18 percent of LASIK procedures in the United States were all-laser procedures that used an IntraLase laser to create the corneal flap, according to the company.

As of October 2008, more than 900 IntraLase FS lasers were in service worldwide and eye doctors had used the technology in more than two million surgical procedures (data on file with Advanced Medical Optics, Inc.)

In recent years, femtosecond lasers produced by other manufacturers have become available. For this reason, the generic term "all-laser LASIK" is preferred when describing blade-free LASIK procedures when the brand of the femtosecond laser used for flap creation is unspecified.

[Read more about IntraLase LASIK.]

Alternative Femtosecond Lasers

Since 2004, femtosecond lasers from three other manufacturers have received FDA approval for commercial use in the United States:

Femtec

The Femtec femtosecond laser (20/10 Perfect Vision AG, Heidelberg, Germany) received FDA approval in 2004. As of October 2008, more than 5,000 surgical procedures have been performed with the Femtec laser worldwide.

A key feature of the Femtec laser is the applanation cone (the part of the laser housing that touches the patient's eye) is curved to adapt to the natural shape of the cornea. This causes less distortion of the cornea during flap creation and less compression of the eye, so there is less increase of intraocular pressure (IOP) during the procedure, according to the company.

The Femtec laser also has the potential to be used for intrastromal refractive surgery, changing the shape of the cornea without cutting a flap, which some surgeons feel may be an alternative to LASIK in the future.

Femto LDV

The Femto LDV femtosecond laser (Ziemer Group AG, Port, Switzerland), formerly called the Da Vinci femtosecond laser, received FDA approval in March 2006. The Femto LDV differs from other femtosecond lasers in that it delivers ultra-short pulses of lower energy, with a very high repetition rate (greater than 1 megahertz).

The Femto LDV's unique method of overlapping low-energy laser spots makes the corneal flap easier to lift with no manipulation of the cornea, say proponents of the system. They also say the Femto LDV produces no inflammation and does not create an opaque bubble layer (OBL) caused by gases injected into the deep stroma of the cornea during the FS laser treatment—a phenomenon caused by other femtosecond lasers that can lead to flap problems and affect visual outcomes after surgery.

As of October 2008, approximately 2,000 Femto LDV procedures have been performed worldwide.

VisuMax

The VisuMax femtosecond laser (Carl Zeiss Meditec, Inc., Dublin, CA.) received FDA approval in January 2007. Like the Femtec laser, the VisuMax femtosecond laser features a curved applanation cone for less corneal distortion, eye compression and IOP increase during the flap creation.

Though the VisuMax laser was commercially introduced only recently in the United States, Zeiss reported in late 2008 that "excellent outcomes" were being achieved with the system when used in combination with the company's MEL 80 excimer laser for all-laser LASIK.

In addition to creating flaps for LASIK, the VisuMax soon may be used to perform a new all-femtosecond laser refractive procedure called femtosecond lenticular extraction (FLEx). In FLEx, the FS laser is used to cut a small lens-like segment of tissue in the cornea. The tissue segment (or lenticule) is then removed from the cornea, thereby changing the shape of the eye to correct nearsightedness.

Cost of All-Laser LASIK

Due to the expense of purchasing and maintaining a femtosecond laser as well as an excimer laser, fees for all-laser LASIK are higher than normal LASIK cost.

Expect to pay approximately $250 to $400 more (per eye) for all-laser LASIK surgery compared to LASIK surgery when a microkeratome is used.

Despite the added cost, most people who opt for all-laser LASIK feel the procedure is a good value due to its advanced technology, the lower risk of flap complications, and the peace-of-mind knowing that no blade will touch their eyes during surgery.

SOURCE: *IntraLase: Coming of age. Cataract Refract Surg Today. 2005:117-120.