This chapter provides an overview of the optical considerations specific to keratorefractive surgery. Refractive surgical procedures performed with the intent to reduce refractive errors can be categorized as corneal (keratorefractive) or intraocular.
Keratorefractive surgical procedures can be divided into surgical-removal, surgical-neutral, and surgical-addition procedures. Surgical-removal procedures include photorefractive keratectomy (PRK), laser subepithelial keratomileusis (LASEK), epithelial laser in situ keratomileusis (epi-LASIK), laser in situ keratomileusis (LASIK), and small-incision lenticule extraction (SMILE). Surgical-neutral procedures include radial keratotomy (RK), astigmatic keratotomy (AK), laser thermal keratoplasty (LTK), and radiofrequency conductive keratoplasty (CK). Surgical-addition procedures include implantation of intracorneal ring segments and corneal inlays. Intraocular refractive procedures include implantation of a phakic intraocular lens (IOL), piggyback lens, and cataract and clear lens extraction with implantation of a monofocal, toric, multifocal, or accommodative intraocular lens.
Although these refractive surgical techniques alter the optical properties of the eye, keratorefractive surgery is generally more likely than lenticular refractive surgery to induce optical aberrations. This chapter discusses only keratorefractive procedures and their optical considerations. For a discussion of optical considerations in lenticular refractive surgery, see BCSC Section 11, Lens and Cataract.
Various optical considerations are relevant to refractive surgery, both in screening patients for candidacy and in evaluating patients with vision complaints after surgery. The following sections address optical considerations related to the change in corneal shape after keratorefractive surgery, issues concerning the angle kappa and pupil size, and the various causes of irregular astigmatism.
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.