Refractive surgery

Refractive surgery is performed to reduce dependence on glasses or contact lenses. Refractive surgical techniques reshape the cornea using incisions, heat, various forms of laser, or implantation of intraocular lenses to decrease myopia (nearsightedness), astigmatism, or hyperopia (farsightedness). The excimer laser is currently the technology of choice for keratorefractive surgeons. The laser can reshape the cornea by ablating the anterior corneal surface in procedures such as photorefractive keratectomy (PRK), and more commonly in laser-assisted in situ keratomileusis (LASIK). In LASIK, the surgeon performs corneal stromal ablation using the excimer laser directed to the corneal tissue under a thin lamellar flap. This flap is created by either a microkeratome or a laser. In order to select the best candidates for refractive surgery, a thorough preoperative history, assessment, and complete eye exam is required. Parameters such as corneal topography, central corneal thickness, degree of refractive error, ocular surface health and patient expectations are all carefully considered in order to determine whether the individual is a good refractive surgical candidate, as well as for selecting the most appropriate procedure. Absolute contraindications to laser vision correction include diagnoses of keratoconus or ectatic corneal dystrophies. Relative systemic contraindications include poorly controlled rheumatoid arthritis and diabetes, pregnancy, and AIDS.