Actual Indications for Intracorneal Ring Segment Implantation in Keratoconus

Intracorneal ring segments (ICRS) are small synthetic implements designed to achieve refractive adjustment by flattening the cornea. Three common types of commercially available ICRS are Intacs, Keraring and Ferrara rings. Low myopia was the initial indication for implantation of ICRS, and indications later included ectatic corneal diseases (such as keratoconus and pellucid marginal degeneration) and ectasia after laser-assisted in situ keratomileusis. Two surgical procedures are used for implantation of ICRS: a mechanical technique, performed using two manual semicircular dissectors, and a femtosecond laser technique, performed with the assistance of femtosecond laser photodisruption for tunnel creation. The design parameters of ICRS, such as shape, thickness and diameter, have different effects on corneal curvature. Several nomograms have been developed in order to improve the outcome of refractive correction, depending on centration of the cone, corneal steepness and refraction. Implantation of ICRS is minimally invasive, although intraoperative and postoperative complications have been reported, depending on the surgical procedure. Combination with other treatment modalities, such as corneal collagen crosslinking and/or photorefractive keratectomy, has also been reported. © 2015 S. Karger AG, Basel Introduction Keratoconus is a progressive, noninflammatory ectatic disorder of the cornea that results in significant protrusion and thinning that are typically diagnosed during the second decade of life. The main symptoms are increasing irregular astigmatism and a decrease in best-corrected visual acuity. Corneal topography may reveal the disease early and is very useful in detecting progression. Inferior corneal steepening is the most common topographic finding. Management of keratoconus includes the use of glasses and contact lenses for visual rehabilitation at early stages, corneal collagen crosslinking (CXL) in the case of progression to achieve stabilization and penetrating or deep lamellar keratoplasty in advanced cases. Intracorneal ring segments (ICRS) are implanted deep into the corneal stroma and were originally used to treat low to moderate myopia [1, 2] . Currently, they are used to manage ectatic corneal disorders such as keratoconus [3, 4] , pellucid marginal degeneration [5] and ectasia after laser-assisted in situ keratomileusis (LASIK) [6] . Güell JL (ed): Cornea. ESASO Course Series. Basel, Karger, 2015, vol 6, pp 66–73 DOI: 10.1159/000381493 Actual Indications for Intracorneal Ring Segment Implantation in Keratoconus