Keratoconus correction using a new model of intrastromal corneal ring segments

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.

Private practice.

Prospective case series.

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 μm 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.

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).

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.