Intracorneal ring segments in ectatic corneal disease – a review
The purpose of this review is to collect and summarize all the scientific literature regarding the use of intracorneal ring segments (ICRS) in corneal ectatic disease. These implants, initially designed to correct myopia in normal eyes, are implanted in the deep corneal stroma with the aim of achieving modifications to the corneal curvature and subsequently refractive adjustments. Colin et al. in 2000 were the first to report the efficacy of these implants in reducing the refractive error and corneal steepening in keratoconus eyes. Two main types of ICRS have been developed and used for the treatment of ectatic corneal disease, different in profile and diameter of implantation: Intacs and Ferrara rings. Successful outcomes have been reported by several authors with these implants in keratoconic eyes using different nomograms. Besides keratoconus, ICRS have been also used successfully for the management of pellucid marginal degeneration and post-laser in situ keratomileusis corneal ectasia. The implantation procedure may be performed today by two surgical techniques to create the corneal channels where implants are inserted: mechanical dissection using a manual semicircular dissector (mechanical-assisted) and photodisruption of lamellar tissue using the femtosecond laser technology (femtosecond-assisted). With both techniques, visual, refractive and topographic improvements have been observed, although higher incidence of intraoperative and postoperative complications have been reported with the mechanical procedure according to the evidence found in the peer-reviewed literature. ICRS technology is a promising therapeutic option in corneal ectatic disease, avoiding corneal graft and allowing a visual and refractive rehabilitation.