Laser eye surgery: PRK, LASIK, Femto-LASIK or ReLEx SMILE?

The 3rd generation of laser eye surgery: ReLEx SMILE is the first painless and flapless method

ReLEx SMILE is the first method which does not require a corneal flap. It was developed in cooperation with the company Carl Zeiss Meditec and introduced for the first time in 2007. In contrast to earlier laser eye surgery methods, only a femtosecond laser is used, the VISUMAX by Zeiss. What makes ReLEx SMILE special is that the correction of the visual impairment is done inside the cornea. The femtosecond laser cleaves a lenticule in the cornea which is then extracted carefully by the surgeon through a 2 mm opening under the surgery microscope in the next step. If you decide to have your eyes lasered with ReLEx SMILE, you should choose an experienced surgeon since the surgeon’s experience plays a significantly larger role for this laser eye surgery method than for other laser techniques. But it is safer, does not cause dry eyes and is therefore ideally suited if you suffer from contact lens intolerance.

The most important advantages are the intraoperative and long-term safety and freedom of pain. The top corneal layer remains intact and the eyes stable during the laser treatment. Only one small step is required to remove the lenticule. Significantly less corneal nerves are severed compared to a method requiring a flap such as LASIK or Femto-LASIK. Flap-related risks and side effects are eliminated.

Our area of application:

• Myopia (sphere) -1.00 to -10.00 dpt
• Corneal curvature up to 5.00 dpt
• Spherical equivalent: -0.75 to -10.00 dpt

Learn more about ReLEx SMILE

With the introduction of the femtosecond laser into refractive surgery, Femto-LASIK was performed for the first time in 2004. The term Femto-LASIK is slightly misleading since the actual correction of the cornea is performed using the excimer laser with this laser eye surgery method as well. The femtosecond laser merely prepares the flap, i. e. the corneal lid. The advantage is that a blade is no longer required and that laser eye surgery using Femto-LASIK is slightly safer that LASIK using the microkeratome. Miscuts can be corrected since the femtosecond laser does not produce smooth cuts but leaves gas bubbles in the tissue with tissue bridges in-between. If these are not severed, the bubbles dissolve and the tissue is as stable as before. Using Femto-LASIK, vision impairments can be corrected more accurately than with LASIK. Wavefront-guided methods are mainly suitable for the correction of an unfavorable laser result. Wavefront-optimized methods, however, are also suitable for the first surgery.

Flap-related risks The corneal flap will never grow attached as tightly as before after the surgery. The cutting surface is only held by adhesion. Scars will only form at the cut edges. This is why the flap can still be lifted off after years, e. g. for another LASIK. It can detach anytime due to external impacts, e. g. sports injuries, pets or accidents. It is a known fact that the scars which form at the edges are more stable with Femto-LASIK than with LASIK.
Learn more about Femto-LASIK.

All LASIK methods cause a dry eye for 3 to 6 months. A dry eye is the most common reason for contact lens intolerance. This is only one of the reasons why with an existing contact lens intolerance, the ReLEx SMILE method should be favored over Femto-LASIK. If contact lenses have to be worn again later in life, e. g. due to presbyopia, this is safely possible thanks to the stability after ReLEx-SMILE surgery.

Area of application:

• Myopia up to -10.00 dpt
• Hyperopia up to +4 dpt
• Corneal curvature up to 5 dpt

Limit area:

• Myopia up to -10.00 dpt
• Hyperopia up to +4 dpt
• Corneal curvature up to 6 dpt

Data measured using aberrometry are used to create a proper personal “map” of the cornea (corneal topography) based on which the excimer laser can perform an even more accurate and tailored correction of laser mistakes.

Wavefront-optimized methods, however, are already suitable for the first use of the laser.

From the 1st generation of laser eye surgery, PRK, to Trans-PRK

The first laser eye surgery performed on humans was photorefractive keratectomy (PRK) using the excimer laser. It was performed for the first time in 1987 and is therefore considered as the first generation of laser eye surgery. With this laser technique, the corneal epithelium is removed mechanically beforehand either using a scalpel, alcohol, a microkeratome or a laser. Then, the top corneal layer underneath is reshaped using an excimer laser. After the laser procedure, a bandage must be worn for several days until the epithelium has regenerated.

The largest drawback is the safety profile: In comparison to the laser techniques that followed, all PRK methods have three things in common: postoperative pain for approx. 4 days, an increased risk of infection and slow vision recovery over 4-6 weeks. For these reasons, we recommend our patients only in exceptional cases having their eyes lasered using these obsolete methods.

Variant of PRK: LASEK – Preparation of the epithelial sheet with alcohol

With laser eye surgery using LASEK (laser-assisted sub-epithelial keratectomy), the epithelium is pre-treated with alcohol, detached manually using special instruments, lifted off and folded away. After the laser surgery, the epithelium is repositioned. The pre-treatment of the epithelium with alcohol can impair healing. A bandage contact lens must be worn for 1 to 3 days, the pain is somewhat less than with PRK and visual acuity is supposed to return quicker.

Variant of PRK: Epi-LASIK – Cutting of the epithelial sheet using the microkeratome

Laser eye surgery using Epi-LASIK (epithelial LASIK) is another advanced variant of PRK which involves less risks than LASIK. With this laser eye surgery technique as well, the entire epithelial sheet is lifted off and folded away to be returned to its original position after the surgery. However, in this case, a similar microkeratome is used as for LASIK. This means that there are no alcohol-related healing impairments as with LASEK but there is a risk of miscuts. In this case as well, visual acuity is supposed to return more quickly.

The higher risk is due to the cut using the microkeratome. With Epi-LASIK, the epithelial sheet is cut using a microkeratome. This means that there is a risk of a miscut which cannot be corrected anymore. We therefore do not recommend Epi-LASIK.
Learn more about PRK, LASEK and epi-LASIK.

Variant of PRK: Trans-PRK – Preparation of the epithelial sheet and vision correction using the excimer laser

With Trans-PRK (transepithelial photorefractive keratectomy), the preparation of the epithelial sheet is usually performed directly together with the ablation to correct the quality of vision using an excimer laser. Essentially the same but in a ‘fancier dress’.

Area of application of all PRK methods :

• Myopia up to -6 dpt
• Astigmatism up to 5 dpt

Limit area of all PRK methods :

• Myopia up to -8 dpt
• Astigmatism up to 6 dpt
• Hyperopia up to 3 dpt

The 2nd generation of laser eye surgery

Since an excimer laser could only be used at the surface of the cornea but the removal of the surface as it was required for PRK causes significant pain and risks, research was conducted into a new method. The idea: removing the top corneal layer underneath the pain-sensitive epithelium of the cornea leaving only a small bridge and folding it to one side like a lid. Then, the MEL 60 was used, a predecessor of the now popular ophthalmological excimer laser, to remove the cornea in the deeper stroma and to correct the impaired vision in this way. This new laser eye surgery technique was called laser-assisted in situ keratomileusis, reshaping of the inner cornea using laser (from ancient Greek Κερατων cornea; Μιλευσισ shaping), LASIK in short. It was first performed in 1989 by Prof. I. Pallikaris at the University of Crete in Greece. This laser eye surgery technique has a relatively flat learning curve for ophthalmologists and is therefore also offered by ophthalmologists who rarely or never perform any other eye surgeries. This could be a disadvantage for the patient if complications occur.

Several million LASIK treatments have already been performed. 90% of the patients are satisfied with the result, 10% suffer from side effects of the flap.

Cutting the flap using the microkeratome. With LASIK the corneal flap is cut using a microkeratome. This means that there is a risk of a miscut which can only be corrected 4 weeks later.

Other flap-related risks The corneal flap will not grow attached as before. The cutting surface is held by adhesion. Scars will form at the cut edges. This is why the flap can still be lifted off after years, e. g. for another LASIK. It can detach anytime due to external impacts, e. g. sports injuries, pets or accidents.

All LASIK methods cause a dry eye for 3 to 6 months. A dry eye is the most common reason for contact lens intolerance. This is only one of the reasons why with an existing contact lens intolerance, the ReLEx SMILE method should be favored over LASIK or Femto-LASIK. Even if contact lenses have to be worn again later in life, e. g. due to presbyopia, this is safely possible thanks to the stability after a ReLEx-SMILE surgery.

Learn more about LASIK.

Area of application:

• Myopia up to -8.00 dpt
• Hyperopia up to +3 dpt
• Corneal curvature up to 5 dpt

Limit area:

• Myopia up to -10,00 dpt
• Hyperopia up to +4 dpt
• Corneal curvature up to 6 dpt

Laser eye surgery in 26 seconds! Christian Schwerdtfeger, newspaper editor at Rheinische Post from Düsseldorf, Germany, researched for one year until he decided to take this step. He mainly focused his research on the risks. With ReLEx SMILE he found the method of his choice and with Dr. Breyer from Düsseldorf the right surgeon: “I deliberately chose a doctor’s office in Düsseldorf which is run by its owner where I could be sure to be treated by the doctor himself and would not have to drive far to have my eyes checked in an emergency.” Why did he have his eyes lasered in the first place? Simple: he says that he was tired of his glasses because they limited him. This is now finally over. Read his testimonial which was published in Rheinische Post on 23 March 2018 in our Blog Blogposting or view his video.