Intrastromal corneal ring segment implantation in paracentral keratoconus with coincident topographic and coma axis

PURPOSE: To evaluate the efficacy, predictability, and safety of implantation of Ferrara-type intrastromal corneal ring segments (ICRS) for refractive correction of paracentral keratoconus. SETTING: Fernandez-Vega Ophthalmological Institute, Oviedo, Spain. DESIGN: Cohort study. METHODS: Snellen uncorrected (UDVA) and corrected (CDVA) distance visual acuities and residual refractive errors were recorded before and 6 months after ICRS implantation for keratoconus. The tunnels for ICRS implantation were created with a femtosecond laser. The power vector and the Alpins method were used to analyze postoperative refractive outcomes. RESULTS: The study evaluated 56 eyes of 49 patients. The mean UDVA was 0.17 +/- 0.14 (SD) preoperatively and 0.41 +/- 0.28 postoperatively and the mean CDVA, 0.70 +/- 0.18 and 0.80 +/- 0.17, respectively (both P<.0001). The efficacy index was 0.60. Five eyes lost 1 line of CDVA, 17 eyes had unchanged CDVA, 15 eyes gained 1 line, 9 eyes gained 2 lines, 7 eyes gained 3 lines, and 3 eyes gained 4 lines. The safety index was 1.14. The spherical equivalent and astigmatism were significantly lower postoperatively than preoperatively (P<.01). Of the eyes, 78.6% were within +/- 1.00 D of the target-induced astigmatism. No intraoperative or postoperative complications occurred. CONCLUSION: Intrastromal corneal ring segment implantation in eyes with paracentral keratoconus provided good visual and refractive outcomes, indicating that it is a predictable and safe procedure for refractive correction in these cases.