Basic knowledge of refractive surgery: correction of refractive errors using modern surgical procedures

Abstract

Introduction: Refractive ophthalmic surgery allows refractive errors to be corrected permanently in a safe, effective, and reliable way with few complications.

Methods: Selective literature review with special reference to the guidelines of the German Commission for Refractive Surgery.

Results: With a total of almost 18 million treatments performed to date, laser in-situ keratomileusis (LASIK) is the most commonly used refractive surgical procedure worldwide. Alternatives to LASIK include surface ablation procedures (PRK, LASEK, Epi-LASIK) and phakic intraocular lens implantation. If ocular accommodation is lost, removal of the crystalline lens and implantation of modern multifocal intraocular lenses (refractive lens exchange) provide an alternative means of correcting myopia, hyperopia and presbyopia.

Discussion: The treatment effect is maximized and complications kept to a minimum if strict inclusion criteria are applied and a high technical standard maintained during the procedure.

Keywords: LASIK; excimer; phakic intraocular lenses; refractive lens exchange; refractive surgery; surface ablation.

Figure 1

Image formation in myopia and hyperopia. In myopia, the image of a point at infinity is projected in front of the retina (I); in hyperopia, the image of a point at infinity is projected behind the retina (II).

Figure 2

A LASIK procedure with a femtosecond laser and an excimer laser: a) The laser beams are focused, under computer guidance, onto a point lying at a precisely calculated depth (femtosecond laser). b) A flap is created by the concentration of many thousands of individual laser pulses in a single plane. c) The flap is lifted, and the refractive error is corrected with the argon fluoride excimer laser. d) Finally, the flap is repositioned.

Figure 3

Limbal relaxation incision (LRI) at the edge of the cornea to correct astigmatism

Figure 4

Foldable phakic intraocular lenses in situ: a) angle-supported, b) iris-fixated, c) sitting in the posterior chamber.

Figure 5

Refractive lens exchange: a multifocal intraocular lens with apodized diffractive structure of the anterior lens surface, in situ, for both near and far vision

Figure 6

Indications for refractive surgical techniques depending on the axially symmetrical refractive error (dark shading = ideal indication, lighter shading = possible indication); RLE, refractive lens exchange, IOL, intraocular lens, PRK, photorefractive keratotomy; modified from (6).

Figure 7

Indications for refractive surgical techniques depending on the severity of astigmatism; LRI, limbal relaxation incision, AK, astigmatic keratotomy, IOL, intraocular lens, PRK, photorefractive keratotomy; modified from (6).