PURPOSE: To evaluate the available evidence on the effectiveness of intrastromal corneal rings (ICRs) in the treatment of adults with keratoconus. METHODS: A systematic review of electronic databases was completed through July 30, 2017. All primary research articles in which adults with keratoconus were treated with ICRs were included. Two independent reviewers assessed methodological quality and classified the studies into high, low, or undefined risk of bias. The measured variables assessed were visual acuity, refraction, keratometry, ring type, and complications. RESULTS: The initial search yielded 442 scientific articles, 62 articles were read extensively, and 18 articles were assessed for eligibility and included for statistical analysis and quality assessment. A total of 1,325 eyes were analyzed, and the results were evaluated preoperatively and at 12 months of follow-up. Uncorrected distance visual acuity (UDVA) improved 0.23 ± 0.28 logMAR and corrected distance visual acuity (CDVA) improved 0.06 ± 0.21 logMAR. Sphere improved 2.81 ± 1.54 diopters (D), cylinder improved 1.49 ± 0.83 D, and mean keratometry improved 3.41 ± 2.13 D within 12 months of follow-up. ICR implantation combined with corneal crosslinking improved UDVA, refraction, and keratometry to a greater degree than ICR implantation alone. CONCLUSIONS: The studies analyzed demonstrate refractive and visual improvement of patients treated with the ICR implantation technique. However, description of the methodological process necessary to evaluate the bias effectively is insufficient.