Intrastromal corneal ring segment implantation in paracentral keratoconus with perpendicular topographic astigmatism and comatic axis.

Purpose: To evaluate the outcomes of implanting intrastromal corneal ring segment (ICRS) using two different strategies in a specific paracentral keratoconus phenotype.
Methods: Eighty-nine eyes with paracentral keratoconus with perpendicular topographic astigmatism and comatic axes were evaluated before and after implanting a 150° arc-length ICRS. Patients were divided into two groups according to the axis where the ICRS was implanted: Group I: comatic axis and Group II: flat topographic axis. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refractive errors, and root mean square (RMS) for coma-like aberration were recorded. The postoperative follow-up was 1 year.
Results: Mean UDVA (logMAR) changed from 0.49 ± 0.37 preoperatively to 0.30 ± 0.32 6 months afterwards ( p  < 0.001) in the group I and from 0.53 ± 0.34 to 0.37 ± 0.35 ( p  < 0.001), in the group II. Mean CDVA in group I changed from 0.11 ± 0.18 preoperatively to 0.06 ± 0.14 6 months after surgery ( p  < 0.001). In group II the improvement did not reach statistical significance (from 0.09 ± 0.10 to 0.07 ± 0.09; p  = 0.06). No eyes lost lines of CDVA in group I. Eight eyes (15.7%) lost lines of CDVA in group II. The spherical equivalent decreased after surgery in both groups ( p  < 0.001). The RMS for corneal coma-like aberration only decreased in the group I ( p  < 0.001).
Conclusion: Both strategies provided safe and effective visual and refractive outcomes in the specific keratoconus phenotype analyzed. The orthopedic strategy provided better visual outcomes than the refractive one.