Tomographic Findings After Implantation of Ferrara Intrastromal Corneal Ring Segments in Keratoconus

To analyze and compare changes to the anterior and posterior corneal surfaces after Ferrara intracorneal ring segment (ICRS) (AJL, Boecillo, Spain) implantation and to correlate those changes with visual outcomes.

This retrospective case series study comprised consecutive patients with keratoconus implanted with the Ferrara ICRS. Computed tomography scans of the two corneal surfaces were obtained preoperatively and postoperatively with a rotating Scheimpflug imaging system. The Wilcoxon test was used to compare groups, and the Pearson's correlation coefficient was used to measure the strength of the correlation between variables.

The study evaluated 241 eyes in 182 patients with keratoconus. Both corneal surfaces showed statistically significant decreases in average steep keratometry (K2) values, corneal astigmatism, elevation at the apex and at the thinnest point, maximum elevation in the central 4-mm area, and elevation inside the 3- and 4-mm zones and at the 3-mm ring. Regarding anterior surface parameters, a significant decrease was observed in flat keratometry (K1), whereas asphericity increased. On the posterior corneal surface, no significant changes in K1 and asphericity were observed. Poor correlation was found between visual outcomes and changes in tomographic parameters. The best correlation was obtained for anterior corneal astigmatism.

ICRS implantation led to statistically significant changes in both anterior and posterior corneal surfaces. However, correlation between visual outcomes and tomographic parameters was poor. [J Refract Surg. 2017;33(2):110-115.].