The shape of the surface of the cornea is changed with the excimer laser. The laser beam vaporises away microscopic layers of tissue to reshape the cornea and correct focusing problems.
This is a more simplified version of Lasik. No cut (flap) is made. The laser treatment is done on the surface of the cornea. Only the epithelial layer is removed with a scrubber (like a modified toothbrush) or a blade. This does however leave a “raw” surface on the cornea which is a bit painful for the first few days. The vision can sometimes take a few weeks to return to normal. For a few years, this procedure is not done unless there is a specific reason to do so. In the hands of an experienced surgeon theLasik procedure was superior to PRK. But, in recent years PRK has made a come back. Instruments and lasers have improved. The healing time is much shorter an less painful. It is a safer procedure than Lasik and a wider range of refractive errors are treatable by PRK.