PURPOSE: To analyze whether implantation of intrastromal corneal ring segments (ICRS) influences the progression of keratoconus in young patients. SETTING: Vissum Corporation, Alicante, Spain. DESIGN: Retrospective case series. METHODS: Eyes with confirmed progressive keratoconus and ICRS (Intacs or Keraring) were evaluated. The visual, refractive, topographic, and aberrometric outcomes were assessed at 2 preoperative examinations to confirm the progressive nature of each case. The postoperative follow-up was 5 years. RESULTS: The study evaluated 18 eyes in 15 patients with a mean age of 25.75 years +/- 3.59 (SD). All the visual, refractive, and topographic measurements worsened between the 2 preoperative examinations, confirming the progressive nature of the cases. Six months postoperatively, there was improvement in the uncorrected and corrected distance visual acuities (P >.05) and all refractive measurements (P <.05) and the mean keratometry (K) was reduced by 4.48 diopters (D) (P <.01). Immediately after the procedure, the visual and refractive variables improved but then worsened. From 6 months postoperatively to 5 years, the mean K value regressed 3.36 D. CONCLUSION: Implantation of ICRS significantly improved the visual, refractive, and topographic parameters in the short term; however, the regression at 5 years suggests that implantation of ICRS does not significantly influence progressive keratoconus in young patients with confirmed progression of the disease. (C) 2015 ASCRS and ESCRS