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

Abstract

To evaluate the short-term outcomes of femtosecond laser-assisted implantation of a 340-degree intracorneal ring (ICR) (Keraring) in patients with keratoconus. Four centers in Iran. Prospective case series. All cases had implantation of the 340-degree ICRafter 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 Kwere evaluated preoperatively and 1, 3, and 6months postoperatively. Eighteen eyes of 17 patients were included. The mean follow-up was 4.33months (range 1 to 6months). 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. 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.