The EuroEyes Clinics were the first eye clinics in Germany
to apply the IntraLase FS femto- second laser to refractive
surgery (Fig. 1). Whereas traditional LASIK uses a microkera-tome
(micro-blade) to cut the corneal flap, IntraLase produces
the flap by using a laser. By replacing the mechanical microkeratome
with a femto-second laser, IntraLase makes it possible to
perform a complete LASIK treatment without using hand-held
mechanical devices.
In 2001, the IntraLase FS femtosecond laser used by EuroEyes
was the only laser of its kind to be FDA approved by the American
Food and Drug Administration. There have been over 200 000
successful IntraLase procedures performed in the United States.
What is a Femtosecond
Laser?
A 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 impulses of light
(10-15 seconds) that last only a quadrillionth of a second
to create a spot as tiny as 1/100mm. To illustrate the extremely
short pulse time: Light travels 7.5 times around the earth
in one second, however, only one half of the thickness of
a hair in a femtosecond!
What does the patient feel?
Treatment is under topical anesthetic (drops)
Preparation of the flap is completely free of pain
Patient can't see the laser beam
Procedure lasts 40-50 seconds per eye
How IntraLase works:
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 that 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.
IntraLase prepares the corneal flap with a laser rather than a mechanical keratome. Contrary to traditional lasers, the energy of the laser beam from a femtosecond laser doesn't affect the tissue on the surface of the cornea, but rather 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 such that tissue is gently separated. 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
depth location 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.3c).
Application of the Femtosecond Laser:
LASIK surgeries: For patients with thinner corneas or
a higher nearsightedness or farsightedness
Diseases such as opacities in the cornea or warping of
the cornea
Reliable and gentle preparations of corneal flaps for
LASIK treatments
What are the advantages of IntraLase
with respect to traditional LASIK?
Ability to Avoid Cut-related Side Effects
Fig. 4a: Traditional LASIK: Corneal
flap with the microkeratome has a thin center
Fig. 4b: IntraLase: Flap is parallel
such that central thickness is exactly the same as peripheral
Corneal flaps that were traditionally made 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 one must wait to complete the treatment at a later date. In comparison, parallel flaps are prepared with IntraLase such that the center is exactly the same thickness as the periphery (Fig. 4b). Therefore, there are no side effects when preparing the flap with IntraLase.
Precision of the Flap Thickness
The femtosecond laser is able to produce a much more reliable and precise corneal flap than a microkeratome. A femtosecond laser can create a flap within 10µm of the desired thickness whereas the traditional keratome is only accurate within 20-40µm. IntraLase offers more security to its patients even though side effects are very rare when using a microkeratome (1:1000).
High Nearsightedness, Thin Cornea
IntraLase offers the opportunity to treat patients with a very thin cornea or a very high nearsightedness who previously weren't candidates with a microkeratome. The precision of IntraLase allows a thinner flap to be created such that more underlying tissue remains available to treat higher amounts of nearsightedness.
