Keratoconus Management by Insertion of an Allograft Corneal Ring Segment (KeraNatural)

Keratoconus is a bilateral corneal ectatic disorder characterized by local biomechanical weakness, corneal thinning, protrusion [1], asymmetrical irregular corneal astigmatism, marked anterior and posterior elevation coinciding with the thinnest point at pachymetry, and compensatory thinning of the corneal epithelium at the cone area [2], resulting in deterioration of vision [3]. In advanced cases with no clinically significant opacities or hydrops, the implantation of intracorneal ring segments for the treatment of keratoconus was first proposed by Colin et al. [4] as an alternative for selected cases and complimentary to penetrating and lamellar keratoplasty for patients with contact lens intolerance. Unfortunately, polymethyl methacrylate (PMMA) implants, although quite effective, bare a high complication rate, up to 30% [5], [6]. The implantation of corneal allogenic intrastromal ring segments (CAIRS) was introduced by Jacob et al. [7] as a safe and effective alternative to the artificial rigid ring segments of different shapes and sizes, inducing similar flattening effects on the protruding keratoconic cornea without the possibility of serious complications like extrusion, perforation, and corneal melting often encountered by the implantation of rigid artificial implants. The aim of this report was to present the technique and results of the first implantation of a precut sterile allograft corneal ring segment (KeraNatural, VisionGift, Portland, OR, USA) in Switzerland for the management of keratoconus.