LASIK
The abbreviation LASIK, freely interpreted, corresponds to "modification of the shape of the interior of the cornea through treatment with a laser beam". Contrary to PRK, LASEK, and EPI-LASIK, this method avoids the ablation of tissue of the outer layer of the cornea, because the ablation is performed inside the cornea.
To get inside the cornea, a thin lamella, the so-called corneal flap, is first cut out with a microkeratome (high precision device with a blade), and flapped back. The deeper layers of cornea thus exposed can now be shaped by the Excimer laser beam according to the refraction defect to be corrected. Even the minutest eye movements are recorded immediately with special 3D-eye-tracking system, and the laser therefore always hits exactly right spot on the cornea. Finally, the flap is put back into place and reattaches by itself within a very short time
The actual laser treatment lasts only a few minutes and is virtually painless. Before the operation, eye drops are used to render the eyes insensitive to pain.
Treatment steps in the LASIK method
For the preparation of the corneal flap we have two types of computer-controlled microkeratomes at our disposal. The operating surgeon decides which one to chose, according to the anatomic condition of the eye. The operating time is the same with the two microkeratomes.
1. Preparation of the flap with the microkeratome
A suction ring is attached to the eye: at the beginning of the treatment, a suction ring is placed on the eye. It maintains the eye in place and serves as a guide for the microkeratome. This procedure entails a slight pressure on the eye. The eye is made insensitive with eye drops, while the eyelids are maintained open by an eyelid holder to avoid involuntary eyelid movements.
Preparation of the corneal flap: an automatically controlled microkeratome cuts out a corneal lamella, of about 0.14 mm thickness.
(Alternatively, this corneal flap can also be prepared using a femtosecond laser. The method is then called Femto-LASIK.)
2. Exposing the treatment plane
The corneal flap is folded back for the treatment with the Excimer laser, like the cover of a book.
3. Ablation of corneal tissue with the Excimer laser to correct the visual defect
Excimer laser
Treatment by Excimer laser: the corneal tissue laid bare is shaped with the Excimer laser to correct the visual defect.
The corneal ablation is performed according to the mode selected (customized LASIK, special laser programs).
The active eye-tracking system ensures that the laser pulses hit exactly the predetermined targets in the cornea, even in case of involuntary eye movements of the patient.
Control of the treatment during the operation: an online pachymeter (device to measure thickness) monitors the preparation of the corneal flap to a precision of a thousandth of a millimeter, without direct contact and under control of special software, as well as the ablation of corneal tissue by the Excimer laser. The attending physician therefore has a supplementary means to verify that the treatment progresses according to plan.
4. Conclusion of the treatment
Once the treatment with the Excimer laser is completed, the corneal flap is put back into place. It reattaches spontaneously to the underlying corneal layers, a suture is not necessary.
The corneal flap acts as a natural organic wound dressing and exerts a positive effect on the healing process: as a rule the patient does not feel any pain.
The external corneal layer (the epithelium) which was partially sectioned, regenerates by itself completely within a few days and closes the wound.
Properties and advantages of the LASIK method
The advantage of the LASIK method is that no real wound is made on the corneal surface, and there is therefore no wound-healing pain after the operation. You can leave the eye laser center after 1 to 2 hours, without any eye bandage. Your visual acuity will already be good enough for you to be able to travel by public transport – but we still recommend that you have somebody at hand to accompany you on your way home. Also, you should not drive on the first day.
The LASIK method permits to obtain precise and lasting corrections of myopia until ca. - 8 diopters and hyperopia up to ca. 4 diopters, and simultaneously of an astigmatism, if also present, of up to 5 diopters, depending on thickness and curvature of the cornea.
• Very high precision and stability of the result obtained
• Correction of the visual defect inside the cornea
• No pain during the operation
• Very short recovery time, a few hours to days
• A further correction can be performed later
