The PRK process uses an excimer laser to sculpt an area 5 to 9 millimeters in diameter on the surface of the eye. This process removes only 5-10% of the thickness of the cornea for mild to moderate myopia and up to 30% for extreme myopia - about the thickness of 1 to 3 human hairs. The major benefit of this procedure is that the integrity and the strength of the corneal dome is retained. The excimer laser is set at a wavelength of 193nm, which can remove a microscopic corneal cell layer without damaging any adjoining cells. This allows the practitioner to make extremely accurate and specific modifications to the cornea with little trauma to the eye.
This ability to sculpt, rather than cut, opens up the arena for treating additional vision conditions. At this stage, there are excimer laser machines that with a combination of masks and computer controls, can reliably treat myopia, hyperopia and now astigmatism.