Comparison of Femtosecond Laser versus Mechanical Intrastromal Corneal Ring Segment Implantation in Keratoconus: A Randomized Clinical Trial Study

Purpose: To compare visual, refractive, and corneal aberrometric outcomes and complications of mechanical and and femtosecond laser-assisted tunnel creation for intrastromal corneal ring segments (ICRS) in keratoconic eyes. Methods: In this prospective study, 56 keratoconic patients were randomly assigned to have ICRS tunnel creation by a mechanical device or a femtosecond laser. Keraring ICRS with a 0.5 mm diameter and different degree arc length were implanted in all cases. All patients had contact lens intolerance and clear central corneas with moderate to severe keratoconus. A complete ophthalmic examination, including uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), manifest refraction, keratometric readings (orbscan II), ultrasound pachymetry, slitlamp examination were performed before and after surgery. All 3, 6, and 12-month follow-ups were completed and the data in the mechanical group and the femtosecond group were compared statistically. Results: One year postoperatively, significant improvement was observed regarding the mean UCDVA and CDVA (both p<.001). Keratometry readings, SE, and manifest sphere improved in both groups at 3, 6, and 12 months (p<.001). The mean reduction in maximum keratometry was 6.38 diopters (D) in mechanical group and 7.04 D in femtosecond laser group. The mean reduction in SE was 4.17 D and 5.47 D, respectively. There was significant improvement in cylinder in femtosecond laser group at 12 months and in mechanical group at 3,6, and 12 months. The reduction in cylinder was significantly greater in femtosecond laser group at 6 months (p=.027). There was no statistically significant difference between the two groups in visual or refractive results (p> .05). Bacterial keratitis, superficial segment placement, and segment extrusion in 1 eye, and white sterile deposition in 5 eyes occurred in the mechanical group. Conclusion: Similar visual and refractive outcomes were achieved by implanting a ICRS using mechanical and femtosecond laser assisted procedures, despite more intraoperative complications in mechanical group.