Implantation of a complete intrastromal corneal ring at 2 different stromal depths in keratoconus

The aim of this study was to evaluate the clinical outcomes of intrastromal MyoRing (Dioptex, GmbH, Linz, Austria) implantation at 2 different depths of 250 and 300 μm.

This was a prospective interventional randomized controlled trial, a pilot study. Keratoconic patients with keratometry values between 48 and 52 diopters were randomly divided into 2 groups. A continuous intrastromal corneal ring of the same size was implanted at 2 different stromal depths of 250 μm (group 1) and 300 μm (group 2) using femtosecond laser technology for both groups. Visual and refractive outcomes, keratometry, corneal biomechanical characteristics, and higher order aberrations were compared at the 1-year postoperative follow-up.

In both groups, uncorrected distance visual acuity significantly improved after MyoRing implantation, whereas neither of these showed any improvement in the corrected distance visual acuity. In addition, the mean central keratometry and spherical and cylindrical refraction reduced significantly in both groups, and spherical aberration increased significantly in both groups. On one hand, coma was reduced almost significantly in both groups, and on the other hand, corneal hysteresis and corneal resistance factor did not change significantly after the operation. None of the patients in both groups had intraoperative or postoperative complications. There were no differences observed in any of the measured variables of the 2 study groups.

An implantation depth of 250 μm has comparable outcomes with the previously applied 300-μm implantation depth. It may be appropriate for selected cases of keratoconus with lower pachymetry.