All Laser LASIK - Blade Free LASIK - Intralase

The first step in LASIK is to separate a layer of the cornea from the underlying cornea so that the stromal layer of the cornea is exposed.   A corneal flap is created that is still attached by a "hinge" of tissue.  The flap is then folded back and very small areas of the underlying tissue are removed (ablated) with an excimer laser in order to change the shape of the cornea so it can better focus light onto the retina.  Once the correct corneal curvature is created, the corneal flap is laid back in place covering the area where the tissue was removed.  The flap acts as a bandage to decrease pain and healing time. 

The difference between conventional LASIK (with a mechanical microkeratome) and all laser (blade-free) LASIK is the method used to create the corneal flap.  Creating the corneal flap is where the majority of complications arise during a LASIK procedure.   In conventional LASIK, the flap is made with an instrument called a microkeratome, which suctions onto the eye and has an oscillating blade.

In 1999 another method of cutting the flap was introduced which uses a laser.  The laser is called a femtosecond (FS) laser and it has special characteristics that make it perfect for creating a corneal flap.  The laser power is emitted in ultrafast pulses (one quadrillionth of a second or 10^-15), which destroy a very specific area of tissue within the cornea without transferring heat or harming any surrounding tissue.  This laser can be programmed to penetrate a certain depth creating a uniform flap of specific thickness.  The creation of the flap can be customized for the individual patient.

You may hear this procedure referred to as "Intralase" after the first laser manufacturer to receive FDA approval in the United States.  Intralase has come out with several new models since then and is now owned by Abbott Medical Optics, which has combined the intralase FS laser with the CustomVue Visx excimer laser and is branding their version of an all laser procedure as iLASIK.  The intralase laser can be combined with any other approved excimer laser for the bladeless lasik procedure.  There are three additional FS lasers that have been approved for bladeless lasik.  ZLasik refers to the portable Zeimer Femto LDV laser that was approved in 2008, the Femtec laser was approved in 2004, and the VisuMax was approved in 2007.  Those three can also be combined with any excimer laser to perform an all-laser LASIK . 

BLADE VS BLADE FREE LASIK

There is an ongoing debate among surgeons whether bladeless is safer than traditional LASIK.  Many doctors believe there is less chance of flap complications using this method because the femtosecond laser is extraordinarily accurate.  Others believe it is just as safe and accurate as traditional LASIK but not any more so and not worth the additional cost.  Many studies have been performed and the results vary.  Some show significantly better results with bladeless and some show that there is not a significant difference between the two.  Bladeless LASIK definitely is safer for patients with thinner corneas who may not have been ideal candidates for traditional LASIK.   The debate on accuracy may continue, however most doctors with considerable LASIK experience believe that the complications that can rarely occur with conventional flap creation could have been avoided if a femtosecond laser would have been used.  In our opinion, all laser/blade free is by far the safest LASIK procedure.

Advantages of all Laser LASIK

The femtosecond laser (all laser procedure) has the ability to create a much thinner flap with a vertical edge (instead of a slanted edge) which is thought to cause less epithelial ingrowth and less chance of the flap dislodging after surgery. 

Less chance of EPITHELIAL INGROWTH

• The outermost layer of the cornea is called the epithelium and cells from the epithelium can sometimes start to grow under the flap causing it to lift up which creates an irregular surface and possibly a distorted image. This is a benign complication that can be treated by lifting the flap again and clearing out all remaining cells.

                                                                    Epithelial Ingrowth

 Less chance of FLAP DISLODGING

• When the flap is replaced over the cornea there is nothing to hold it in place at first. The corneal epithelium begins to regenerate immediately along the edge of the flap but the cornea is still very vulnerable at this stage which can take up to 14 days. Over the next 3 to 4 weeks the epithelium will begin to lay down a basement membrane in order to create more stability but trauma could still dislodge the flap. Once the basement membrane is down, the corneal cells will begin to secrete an adhesive protein in order to bond the flap to the cornea below and this process could take up to 10 weeks. So for the first 3 months after surgery the cornea is more vulnerable than before. The FS laser creates a customized vertical edge on the flap or an inverted bevel so it fits into place more tightly and is less likely to be dislodged. The femtosecond laser promotes flap stability and positioning superior to a mechanical microkeratome.

Less chance of BUTTONHOLE FLAP

• A "buttonhole" flap is an improperly formed flap where the center of the flap remains adhered. This can cause some permanent loss in best corrected vision. There is a much greater chance of this happening with a mechanical microkeratome and is virtually impossible with a femtosecond laser. 

                                                        Button-hole Corneal Flap

MORE PRECISE FLAP THICKNESS / ability to cut a THINNER FLAP

• When the laser strikes the cornea it is removing tissue by breaking the molecular bonds. The cornea must maintain a certain thickness after the LASIK procedure so the advantage of having a thin flap is that you have more corneal tissue left over. A normal cornea is 500 to 600 microns thick and the FS laser is able to create a flap as thin as 100 microns.
• The FS laser also has the ability to make a custom flap. It can be oval or round and the flap hinge can be put at any location 360 degrees around the cornea. This would be beneficial for someone who may have an irregular cornea which excludes them as a candidate for traditional LASIK.

Reduced chance of Corneal Ectasia

As mentioned above, the cornea must maintain a certain thickness after the procedure.  If the underlying cornea becomes too thin corneal ectasia (bulging of the cornea) can be induced.  This is a very serious complication that results in decreased best corrected vision and possibly the need for a future corneal transplant.  Because a traditional microkeratome is not as accurate as a femtosecond laser, it can cut too deep without the surgeon knowing it until after the procedure.  The extra deep incision (caused by mechanical mistake) to create the corneal flap plus the laser ablation to reshape the cornea could ultimately result in corneal ectasia.  This is not a problem with a femtosecond all laser LASIK procedure.

Lower Amount of Induced Higher Order Aberrations

According to a study in 2005 in the Journal of Cataract & Refractive Surgery entitled "Femtosecond laser versus mechanical keratome flaps in wavefront-guided in situ keratomileusis: prospective contralateral eye study." By Durrie and Kezirian the Femtosecond Laser causes fewer higher order aberrations compared to a mechanical microkeratome.  That equates to sharper, clearer vision and contrast sensitivity and possibly less glare and halos at night.

DISADVANTAGES of All Laser LASIK

• Transient Light Sensitivity
• Some people (about 1%) experience extreme light sensitivity after blade-free lasik. This is not vision threatening and resolves in a few weeks with topical steroid treatment.
• Higher Cost

Are You a Candidate for All Laser LASIK?

The same qualifications that are needed for conventional LASIK are also required for an all-laser procedure.

• You should be over 21 years old
• You should have a stable prescription for at least one year
• There are certain eye diseases or disorders such as keratoconus, which will exclude you as a candidate for LASIK. Other conditions such as dry eye or conjunctivitis may need to be treated before you have surgery.
• Are you pregnant? Pregnancy hormones can change your prescription and make your eyes dry so it's better to wait to have LASIK.
• Your prescription must be within a certain range and this is decided on an individual basis considering corneal thickness.
• There are certain autoimmune and degenerative diseases that may disqualify you such as rheumatoid arthritis, type 1 diabetes, and Sjogren's syndrome.

CUSTOM LASIK and All Laser LASIK

Custom LASIK is also known as wavefront guided LASIK.  LASIK corrects our vision when we are nearsighted, farsighted or have astigmatism.  These are all considered lower-order aberrations.  Although LASIK corrects the lower-order aberrations, it can also induce some higher-order aberrations like spherical aberration and coma which result in halos, glare, or decreased contrast sensitivity all of which greatly decrease night vision.  Custom LASIK was created to reduce the higher-order aberrations that are inherent in the human visual system and those aberrations that can possibly be induced by the LASIK procedure.  It works by using a wavefront analyzer to take a 3-D topographical map of the cornea before surgery.  Light is sent into the eye and bounces off the retina, returning back through the cornea to the wavefront analyzer, which then creates an accurate map.  This information is sent directly to the excimer laser before surgery.  Custom LASIK can potentially improve the quality of vision when compared with non-custom LASIK.  Some studies have shown that creating the flap with an FS laser does not worsen the eye's higher order aberrations and therefore is ideal for use with custom LASIK. 

LASIK ENHANCEMENT

LASIK surgery is meant to decrease dependence on contact lenses or glasses.  The visual result will not always be perfect but it should be enough to function without the need of additional correction.  The vision may take weeks to months to completely improve, but if it does not then an enhancement may be required.  There are many factors affecting the outcome or satisfaction after surgery including the shape of corneas, refractive error, tear quality, age and expectations.  If an enhancement is needed then the eyes will be evaluated the same way they were before the first procedure.  If it is safe to proceed, then the procedure is performed almost the same way.  The only difference is that the flap is lifted at the same point with a special tool so no cutting is necessary.  Enhancements are usually included in the price for a certain time limit.  If a surgeon does more enhancements it does not necessarily mean they are not as accurate as others.  Some surgeons do more enhancements in order to get better results while others will only do an enhancement if the vision is very reduced.  The rate of enhancements is also dependent on the types of patients and each individual situation will be different.  It has been demonstrated in certain studies that the rate of enhancements is lower with blade-free lasik due to better refractive outcomes.