Tissue Addition or Subtraction Techniques
With the exception of laser ablation techniques (discussed in the section Laser Biophysics), lamellar procedures that alter corneal shape through tissue addition or subtraction are primarily of historical interest only. Keratomileusis for myopia was originated by Barraquer as “carving” of the anterior surface of the cornea. It is defined as a method to modify the spherical or meridional surface of a healthy cornea by tissue subtraction. Epikeratoplasty (sometimes called epikeratophakia) adds a precision lathed lenticule of donor tissue to the corneal surface to induce hyperopic or myopic changes. Keratophakia requires the addition of a tissue lenticule or synthetic inlay intrastromally (see Chapter 4). There is, however, recurring interest in femtosecond laser techniques to excise intrastromal lenticules to alter corneal curvature without the need for excimer laser ablation. These procedures are termed refractive lenticule extraction (ReLEx), femtosecond lenticule extraction(FLEx), and small-incision lenticule extraction (SMILE). For more detailed discussion of these procedures, see Chapter 12.
Excerpted from BCSC 2020-2021 series: Section 13 - Refractive Surgery. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.