Related Experiment Video
Updated: May 19, 2026
Three Different Protocols of Corneal Collagen Crosslinking in Keratoconus: Conventional, Accelerated and Iontophoresis
Published on: November 12, 2015
Intrastromal corneal ring segment implantation in paracentral keratoconus with coincident topographic and coma axis
José F Alfonso1, Carlos Lisa, Jesus Merayo-Lloves
1Instituto Oftalmológico Fernández-Vega, Avenida Doctores Fernández-Vega 114, 33012 Oviedo, Spain. j.alfonso@fernandez-vega.com
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:
Fernández-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.
