If you are nearsighted, the vision, you may need glasses, prk instructions, to see clearly. There is a small risk that the failure mechanisms, such as blurred or dim vision, are persistent. If you wear contact lenses should stop wearing them for a certain period before the first visit or study. PRK photorefractive keratectomy is a process of refraction on the surface of the epithelium surface layer of the cornea in the excimer laser, rotating brushes or by using 20% alcohol.