Femtosecond-LASIK

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The Femtosecond laser, or abbreviated Femto-LASIK, is an advanced form of LASIK. It is currently the most precise technological method of creating the corneal lamella (flap) for the following laser procedure. EuroEyes is one of the leading clinical groups within this area. The femto laser technology equals even more safety and precision. The femtosecond laser is more gentle to the corneal tissue, making it possible for patients with thin corneas, or patients with higher visual deficiencies, to get an optimal and safe treatment.

The Progress of the Femtosecond LASIK

What is a Femtosecond Laser?

The femtosecond laser is an infrared laser that can treat tissue very precisely with significantly less heat created than other laser treatments - a big advantage in eye laser surgery. Femtosecond lasers work with ultra-short light impulses (10-15 seconds) that needs only a billionth of a second to create a

spot as tiny as 1/100mm. To illustrate the extremely short pulse time: In one second, light travels 7.5 times around the earth, however, in one femtosecond, it only travels one half of the thickness of a hair!

What does the patient feel?

- The treatment is performed under local anaesthetic eye drops
- The reparation of the flap is completely painless
- The patient can not see the laser beam
- The procedure lasts 40-50 seconds per eye

How does Femto LASIK work?

Traditional LASIK uses a microkeratome (micro-blade) in the first step to cut the corneal flap that is opened up to expose the deeper underlying corneal tissue. This is then treated in a second step by an excimer laser. The flap is then laid back in place and protects the area where corneal tissue was removed. The corneal flap is prepared with a laser rather than a mechanical keratome. Contrary to traditional lasers, the energy of the laser beam from a femtosecond laser does not affect the tissue on the corneal surface, but reaches a specific predetermined depth inside the cornea. Very high energy levels can be achieved through intense focusing of the laser beam.

The point of focus of the laser beam allows material to be divided at the molecular level (photo-disruption), gently separating the tissue. The surrounding corneal tissue remains undisturbed without damage. The femtosecond laser scans the cornea starting at one edge and works its way towards the other side (Fig. 3a). The laser beam produces a layer of tiny bubbles in exactly the desired location depth of the cornea. This enables the corneal flap to be opened and lifted to the side like in traditional LASIK. The final treatment with and excimer laser is then identical to traditional LASIK (Fig. 3b).

What are the advantages of Femto LASIK compared to traditional LASIK?

Ability to Avoid Cut-related Complications
Corneal flaps that are made the traditional way with the microkeratome are thinner in the centre (Fig. 4a). In rare cases, the flap is so thin that it is not possible to complete the laser treatment immediately, and the patient must wait to complete the treatment at a later date. In comparison, parallel flaps are prepared with IntraLase, ensuring that the center is exactly the same thickness as the periphery (Fig. 4b). Therefore, there are no side effects

when preparing the flap with the femtosecond.

Precision of the Flap Thickness
The femtosecond laser is able to produce a much more reliable and precise corneal flap than the microkeratome. A femtosecond laser can create a flap within 10μm of the desired thickness, whereas the traditional keratome is only accurate within 20-40μm. Femtosecond LASIK offers increased security to its patients even though side effects are very rare when using a microkeratome (1:1000).

The laser energy is focused in an exact predetermined corneal depth

The laser energy is focused in an exact predetermined corneal depth. A micro-plasma is formed, which vaporizes a corneal ball of tissue with a diameter of approximately 1 μm (1 micrometer).

A micro bubble of gas and water is generated

A micro bubble consisting of gas and water is generated (diameter: 5 - 12 μm). The bubble expands and separates the surrounding corneal layers.

The photo-disruption results in a mixture of carbon dioxide and water

The photo-disruption results in a mixture of carbon dioxide (CO2) and water. The epithelial pumping action makes sure the latter aspirates. What remains, is the separated corneal tissue.

In sum, thousands of laser impulses separates the corneal lamellae

In sum, thousands of laser impulses separates the corneal lamellae in the entire flap area. Thus, the femtosecond laser has made an incision without ever touching the cornea, and is because of this also called a laser keratome. Subsequently, the flap can easily be flipped over by a blunt spatula.

Microkeratome vs. Femtosecond Laser

Look for yourself: The following two videos demonstrate the preparation of the corneal flaps. One shows the non-contact laser keratome (Femtosecond laser), and the other shows the handheld mechanical knife (Hansatome Microkeratome).