Intrastromal corneal ring segment SK for moderate to severe keratoconus: a case series

To report clinical results and safety profiles of symmetrical intrastromal corneal ring segment (ICRS; Intacs SK, Addition Technology Inc) implantation in eyes with moderate to severe keratoconus.

Interventional case series of 24 eyes from 22 patients implanted with Intacs SK using the femtosecond laser. Evaluation included uncorrected (UDVA) and corrected distance visual acuity (CDVA), manifest refraction, and Placido-based Scheimpflug imaging. Postoperative follow-up was 1 day, 1 week, and 1, 3, and 6 months.

Mean patient age was 28±7 years (range: 16 to 41 years). All eyes had keratoconus. Twenty-one of 24 eyes had 2, 450-μm symmetrical segments inserted. Mean UDVA and CDVA were significantly better at 1, 3, and 6 months postoperatively (UDVA: 20/340 preoperatively vs 20/70 at 6 months [P<.001]; CDVA: 20/70 preoperatively vs 20/40 at 6 months [P<.001]; UDVA analysis of variance [ANOVA]: F=6.46, P=.0057; CDVA ANOVA: F=5.24, P=.0138). Pre- and 6-months postoperative clinical results were: mean spherical equivalent refractive error -9.60±4.86 diopters (D) and -3.05±2.05 D (P<.001), respectively; mean refractive cylinder, -3.20±1.50 D and -1.55±1.10 D, respectively (P<.001); and mean average total corneal power 52.03±4.49 D and 46.95±4.61 D, respectively (P<.001). No complications occurred, and no patients were lost to follow-up. Eyes with steeper preoperative corneal keratometry readings had the greatest flattening in corneal curvature and thus the greatest decrease in myopic refraction (r=-0.4, P<.001). No correlation was found between preoperative thinnest corneal pachymetry and postoperative curvature flattening.

Implantation of Intacs SK for moderate to severe keratoconus is safe and effective, leading to significant decrease in myopia and appreciable decrease in astigmatism with improvement in CDVA.