PTK is an excimer laser surgical procedure that removes roughness or cloudiness from the cornea. The cornea is the smooth clear window of the eye in front of the colored iris that helps bend light rays so they focus directly on the retina, the light-sensing layer of cells at the back of the eye. If the corneal surface is rough or cloudy, the rays of light do not focus properly on the retina and images are blurry.

Until recently, the rough cornea was scraped smooth with a surgical blade, while the cloudy cornea required a partial or full corneal transplant. More recently, phototherapeutic keratectomy, or PTK, is an option.

The excimer laser allows some abnormal corneas to be treated with a cool beam of light that evaporates tissue. The principal advantage of laser surgery over conventional surgery is the laser is able to create a smoother corneal surface than a blade and smaller amounts of tissue can be removed.

Potential complications after PTK include poor wound healing, excessive corneal flattening resulting in farsightedness, and irregular astigmatism or poor vision that cannot be corrected completely with glasses.