Refractive and biomechanical results of intrastromal ring segments for keratoconus

Purpose To analyse the refractive and biomechanical changes in the cornea after implantation of intrastromal ring segments. Methods The study included 43 eyes of 36 patients (mean age 38 years); 7 eyes had received Intacs® and 36 KeraRings®. Visual acuity, spherical equivalent, K readings, corneal hysteresis (CH) and corneal resistance factor (CRF) were measured pre-op, at 6 and at 12 months post-op. CH and CRF were derived from the Ocular Response Analyser (ORA). Results UCVA improved from 1.10 logMAR to 0.65 at 6 months and 0.62 at 12 months post-op. BCVA improved from 0.32 logMAR to 0.25 at 6 months and 0.22 at 12 months post-op. Spherical equivalent improved from -5.28 to -1.30 at 6 months and -1.85 at 12 months post-op. Sim K improved from 5.81 to 3.64 at 6 months and 4.10 at 12 months post-op. Mean K improved from 48.9 to 46.3 at 6 months and 46.7 at 12 months post-op. All changes between pre-op and 6 months post-op were significant, but between 6 months and 12 months they were not. Pre-op CRF (mean 6.37) and CH (mean 7.34) did not change significantly up to 12 months post-op. Conclusion Intrastromal ring segments for keratoconus reduced the spherical equivalent refraction and improved the UCVA and BCVA at 6 months post-op and remained stable up to 12 months. ORA's biomechanical factors CH and CRF did not changed up to 12 months post intrastromal ring segment implantation.