 |
 |
This is the most applied method among the methods specific to the eye. It is mostly used in patients with hyperopia and astigmatism. However, the field it is most useful in is for eyes having undergone previously failed treatment. In such conditions, it corrects the failed or mistreated part of the eye while preserving the successfully treated regions. |
 |
The most important part of this method is the special eye map called topography. This map is recorded with specially-developed devices and can be copied using a special method. |
 |
This map is recorded to a computer disk and transmitted to the computer of the laser that is going to apply the treatment. The disk can only be read by the computer of the laser. |
 |
The laser prepares a detailed treatment plan according to the map it reads. There is also the role of the wavefront method in this plan. The treatment plan will be made by the laser assessing both the wavefront and map results. |
 |
The system determines the shape which the cornea layer is expected to have after treatment, and the treatment is applied.
|
|
The application of the treatment is not different from standard laser applications for the patient. The difference is the preparation of treatment and the feature of the shape that the laser creates on the cornea.
|
|
 |
|
The direct image taken from the cornea and the analyses of this image are found in the general view of the cornea topography map.
|
|
The 3-D view of the cornea is also obtained from this map analysis. The ideal condition of the cornea expected after the laser treatment is reckoned according to these maps.
|
|
If the cornea becomes too steep in this blue circle, the patient will see his surroundings very blurry while seeing the centre very well.
|
|
If the cornea is too flat like in this red circle, the patient will see the surroundings well while seeing the centre or the point he is looking at very blurry.
|
|
If the cornea has a completely round shape, which is thought to be ideal, there will be many focus points as shown in this diagram and the patient will not have excellent vision. |
|
The desired and targeted form of the cornea is this red circle form. If this shape of the cornea can be obtained after the laser treatment, the vision will be perfect. This perfect vision will continue night and day. The surgeon applying the treatment can define the ideal form he determines for the cornea to the computer and conducts the treatment to reach this form in a method called Q-mode or F-CAT.
|
|
 |
WHAT IS THE WAVEFRONT TECHNOLOGY? |
|
After developments in the adaptive optics field were achieved in recent years, the elimination of the distortions disturbing the vision has become possible. Wavefront technology, used for obtaining sharper telescopic views, has begun to be used in ophthalmology to further improve the optical system of the eye.
Wavefront technology measures the aberrations and distortions (accumulation of all the rays in one point bending) and creates a mathematical definition to determine the amounts numerically. Transferring this data to a point-scanning laser such as the Allegretto laser allows you to shape the cornea personally for each patient and to adjust the existing distortions.
|
HOW ARE THE ABERRATIONS MATHEMATICALLY DEFINED?
|
|
The Zernike polynomials are the mathematical definitions of the aberrations (defects) in the sight. Polynomials have different levels and orders. Low-level polynomials comprises myopia, hypermetropia and astigmatism. Low-level aberrations can be easily treated with glasses or standard LASIK treatment. High-level polynomials have been recently defined. Coma, trefoil and spherical aberrations are the most common high-level aberrations. The graphic shows some high-level aberrations (Fig. 3). The wavefront LASIK adjusts the high-level aberrations which cannot be treated with standard LASIK treatment. |
WHO ARE THE CANDIDATES FOR WAVEFRONT LASIK? |
 |
This technology can be used for two groups of patients. The first group is the patient group applying for the standard LASIK treatment. There is evidence of the fact that the Wavefront LASIK provides a higher quality of sight and less night vision side effects. The second group consists of patients who had previously experienced LASIK, PRK, LASEK or other retractive surgeries but continue to have problems. These problems may include night dazzles, halos, sight quality problems or insufficient treatment of sight defects. The cornea width and the overall health condition of the eye are important in determining whether to perform a second operation.
Fig 4. The picture on the left is the wavefront map of an eye with spherical aberration and the one on the right is blurred sight resulting from such disorder.
|
