Long-Term follow-up of a 300° arc-length intrastromal corneal ring segment implantation in central keratoconus

Purpose To evaluate the outcomes of 300° arc-length intrastromal corneal ring segment (ICRS) implantation in central keratoconus throughout a 3-year follow-up period. Methods This study included patients with central keratoconus who exhibited a significant increase in corneal steepness and/or prolateness and underwent 300° arc-length ICRS implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, keratometry, corneal asphericity at 8.0 mm and the root mean square (RMS) for coma-like aberrations for a pupil size of 4.5 mm were recorded preoperatively and at 3, 12, and 36 months postoperatively. Results 131 eyes were included. All eyes were examined at 3 and 12 months postoperatively, and 94 eyes at 36 months. At three months postoperatively, UDVA (logMAR) changed from 0.85 ± 0.34 preoperatively to 0.48 ± 0.27 postoperatively ( p < 0.0001). CDVA rose from 0.23 ± 0.14 to 0.15 ± 0.09 ( p < 0.0001). The mean K-steep from 52.50 ± 3.42 D to 46.82 ± 2.74 D (<0.0001). The RMS for coma-like aberrations decreased from 1.45 ± 0.75 μm to 0.94 ± 0.52 μm postoperatively ( p < 0.0001), and corneal asphericity from −1.31 ± 0.43 to −0.39 ± 0.53 ( p < 0.0001). At 36 months, 6.4% of the eyes lost lines of CDVA compared to preoperatively, while 78.7% of the eyes gained lines of CDVA. The mean flattening in K-steep was 5.16 ± 2.17 D. 83.7% of the eyes had a postoperative K-mean ≤48.0D. The RMS for coma-like aberrations and corneal asphericity remained unchanged over the postoperative period. Conclusion A 300° arc-length ICRS implantation improved the visual acuity and induced a substantial corneal flattening over 3 years in keratoconus with a significantly high corneal steepness and/or prolateness