Keratoconus correction using a new model of intrastromal corneal ring segments

PURPOSE: To evaluate the optical value of a new model of intrastromal corneal ring segments (ICRS) (Keratacx Plus) in patients with keratoconus and to quantify subsequent changes in corneal topography and asphericity. SETTING: Private practice. DESIGN: Prospective case series. METHODS: This study comprised patients who had primary keratoconus or keratectasia after laser in situ keratomileusis (LASIK); none wore contact lenses. Rings were implanted through tunnels created manually or with a femtosecond laser. All eyes had clear visual axes and corneal thickness over 450 mu m at the incision site. Preoperative and postoperative pachymetry images were acquired. Results were analyzed using a matched-pair t test and the Kolmogorov-Smirnov test. RESULTS: Twenty-nine eyes (24 patients; mean age 30.1 years +/- 10.6 [SD]) were evaluated. The ICRS significantly increased uncorrected and corrected visual acuities from 0.05 to 0.16 and from 0.17 to 0.5, respectively (z = 4.7, P<.001). They reduced the median spherical error from -4.0 to -0.5 diopters (D) (P<.001) and median cylindrical error from -4.4 to -2.5 D (P<.001). All topographic parameters were reduced, including maximum keratometry (K) (49.4 D versus 45.1 D), minimum K (49.4 D versus 45.1 D), mean K (51.4 D versus 48.4 D), astigmatism (-2.0 D versus -0.5 D), and asphericity (eccentricity 0.49 versus 0.23) (all P <.001). CONCLUSIONS: The ICRS provided topographic and visual improvement in keratoconus and post-LASIK keratectasia. Variance in surgical outcomes with manual versus femtosecond tunneling and the effect of different ring sizes are yet to be studied. (c) 2016 ASCRS and ESCRS