Femtosecond laser implantation of a 340-degree intrastromal corneal ring segment in keratoconus: Short-term outcomes

Purpose: To evaluate the short-term outcomes of femtosecond laser-assisted implantation of a 340-degree intracorneal ring (ICR) (Keraring) in patients with keratoconus. Setting: Four centers in Iran. Design: Prospective case series. Methods: All cases had implantation of the 340-degree ICR after tunnel creation with a femtosecond laser. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, sphere, cylinder, manifest refraction spherical equivalent (MRSE), mean keratometry (K), steep K, and flat K were evaluated preoperatively and 1, 3, and 6 months postoperatively. Results: Eighteen eyes of 17 patients were included. The mean follow-up was 4.33 months (range 1 to 6 months). The mean UDVA improved from 0.95 logarithm of the minimum angle of resolution (logMAR) +/- 0.33 (SD) to 0.53 +/- 0.35 logMAR (P = .001) and the mean CDVA from 0.39 +/- 0.22 logMAR to 0.26 +/- 0.21 logMAR (P = .09). The mean sphere decreased from -5.08 +/- 3.74 diopters (D) to -1.67 +/- 2.59 D, the mean cylinder from -5.83 +/- 2.02 D to -2.72 +/- 1.81 D, and the mean MRSE from -8.03 +/- 3.88 D to -3.01 +/- 2.82 D (P <.001). The mean K decreased from 51.43 +/- 3.59 D to 47.42 +/- 3.59 D (P<.001). All patients with a preoperative mean K greater than 55.0 D had worse CDVA. Conclusions: Implantation of a 340-degree ICR using femtosecond laser improved the visual, refractive, and topographic parameters in keratoconic patients. The findings indicate that patients with severe keratoconus (mean K>55.0 D) are not good candidates for this type of ICR. (C) 2017 ASCRS and ESCRS