Changes in Anterior and Posterior Corneal Parameters in Patients with Keratoconus After Intrastromal Corneal-ring Segment Implantation

Purpose: To compare changes in the anterior and the posterior corneal parameters and the anterior chamber depth (ACD) measured by a rotating Scheimpflug camera and scanning-slit topography before and after intrastromal corneal ring segment (ICRS) implantation. Methods: Twenty-five eyes of 21 keratoconus patients who had Intacs (Addition Technology, Sunnyvale, CA) ICRS implantation were included. The anterior segment parameters of the participants were measured before and 3 months after Intacs ICRS implantation with a rotating Scheimpflug camera and scanning-slit topography. Outcome measures included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction and corneal topography. Results: The UDVA improved in 21 eyes (84%) and CDVA in 18 eyes (72%). The anterior average keratometry decreased from 51.80 D preoperatively to 49.59 D postoperatively (p<0.001) using the rotating Scheimpflug camera and Sim K decreased from 51.21 to 47.44 D using the scanning-slit topography. The posterior average keratometry decreased from -8.03 D preoperatively to -8.42 D postoperatively (p<0.001) using the rotating Scheimpflug camera. ACD decreased from 3.44 to 3.32mm (p<0.001) and from 3.28 to 3.19mm (p<0.001) using the rotating Scheimpflug camera and scanning-slit topography, respectively. Conclusions: The implantation of Intacs segments induced corneal flattening of the anterior surface and corneal steepening of the posterior surface. Both anterior corneal flattening and posterior corneal steepening contributed to the decrease in the keratometric power.