Photorefractive Keratectomy (PRK) is a type of refractive surgery to correct myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. The thin outer layer of your cornea called epithelium is removed before reshaping the underlying corneal tissue with an excimer laser. The epithelium heals itself and grows back over the corneal surface within a few days after the surgery.
In LASIK, a thin flap in your cornea is created using either a microkeratome blade or a femtosecond laser. The surgeon folds back the flap, then removes some corneal tissue underneath using an excimer laser. The flap is then placed back to cover the area where the corneal tissue was removed.
Since light focuses in front of retina in a myopic eye, distant objects appear blurry but close objects appear normal to such persons. This is because light is focused in front of your retina and, being too far forward in the eye, objects in the distance look blurred.
Both nearsightedness and farsightedness are refractive conditions, which measn that they both are problems related to how the light is focused as it enters the eye. Nearsighted (myopia) means that you can see closer or “nearer” and further out gets blurry. Farsighted is simply the opposite of it.
LASIK, or "laser-assisted in situ keratomileusis," is the most commonly performed laser eye surgery to treat myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. It is a type of refractive eye surgery. Most people who have LASIK eye surgery achieve 20/25 vision or better, which is good for most activities.