Laser Vision Correction (LVC) corrects refractive errors such as myopia (short-sightedness), hyperopia (far-sightedness), astigmatism and presbyopia (middle-aged onset far-sightedness). These refractive errors occur when the light rays are brought to a blur focus on the retina.
All laser vision procedures such as TransPRK, LASIK and ReLEx SMILE take place at the cornea. The one exception is Implantable Collamer Lens (ICL) that is actually not a laser vision procedure but an artificial lens implantation procedure that takes place inside the eye, behind the pupil.
The basis of all laser vision procedure is to re-shape the cornea curvature either by the sculpting of cornea stroma tissue (as in TransPRK and LASIK) or the cutting and removal of a stroma tissue lenticule (as in ReLEX SMILE). The reshaped cornea curvature will cause the light rays entering the cornea to be bent to a new sharp focus on the retina.