The most important instrument in laser therapy for the eyes is the so-called excimer laser. These devices have been used in corneal surgery since 1986 and were developed to their current precision by university hospitals in the USA, England and Germany.
The excimer laser is used in various types of surgery, but the principle is always the same: The laser beam hits the surface of the cornea, wearing off wafer-thin layers through vaporisation. The laser is applied to the centre or the edge of the cornea, depending on the type of vision defect. This means that in the case of 
Short-sightedness it is flattened in the centre, and in the case of Astigmatism it is straightened. In the case of Long-sightedness the cornea is ablated in a circle shape around the centre in order to heighten the centre of the curvature.
To restore the necessary refractive power of the eye, the curvature of the cornea is altered in a way that is similar to grinding glass into lenses.
With an eye tracking system, the newest generation of lasers allows treatment at predefined points. The laser follows the movements of the eye and is, therefore, able to precisely hit the area to be ablated. When the eye movements are too extreme, the laser automatically interrupts the treatment. This system ensures a targeted ablation of the cornea and that no injury occurs. In addition, the newest laser systems also detect rolling eyes and compensate for them.
The excimer laser is used in various methods of vision correction. These include laser in situ keratomileusis (LASIK), laser epithelial keratomileusis (LASEK) and photorefractive keratectomy (PRK).
