A 33-year-old woman with irregular astigmatism 6 years after radial keratotomy (RK) for keratoconus was treated with implantation of a single intrastromal corneal ring segment (Keraring) using the femtosecond laser. The segment (0.150 mm thick with a 160-degree arc) was inserted in the steepest area (inferior) with no intraoperative or postoperative complications. Six months postoperatively, the uncorrected visual acuity had improved from 20/40 to 20/25 and the best spectacle-corrected visual acuity, from 20/32 to 20/20. The mean manifest astigmatic correction decreased from -2.50 diopters (D) to -0.75 D, and corneal topography showed improved inferior steepening and less irregular astigmatism. Although the results are encouraging, the long-term effect of this approach in post-RK patients is not known.