In PRK (Photorefractive Keratectomy), no layer of the cornea is removed and no incisions are made. Instead, a small portion of the corneal surface (about 50 microns) is reshaped with a laser. After the procedure, the epithelium heals within a few days. The advantage of this technique is that it causes less damage to the corneal strength, reducing the risk of corneal thinning and irregularities compared to LASIK.