Mid-Term Results of a Single Intrastromal Corneal Ring Segment for Mild to Moderate Progressive Keratoconus.

Purpose: To study the mid-term effects of implanting a single intracorneal ring segment (ICRS) for treatment of mild to moderate progressive keratoconus.

Methods: This retrospective study was conducted on patients with progressive keratoconus treated with ICRS. The mean follow-up time was 15.2 ± 8.8 (range, 7-26) months before and 27.8 ± 7.5 (range, 18-35) months after surgery. Patients received no other treatment during this time. Of the cases studied, 59.1% had inferior keratoconus.

Results: Thirty eyes of 30 patients with a mean age of 27.5 ± 4.6 years were included in the study. Corrected distance visual acuity decreased by 1 line during the preoperative follow-up and improved by 2 lines after surgery (P < 0.05). Maximum keratometry (Kmax) of the anterior (2.39 ± 0.75 D) and posterior (0.33 ± 0.32 D) corneas at 3 mm and anterior Kmax at 8 mm (2.39 ± 0.95 D) decreased after treatment (all P < 0.05). The posterior Q value shifted toward a more oblate curvature (0.50 ± 0.52, P = 0.023). Decreases in anterior elevation at the thinnest point (5.22 ± 7.21 μm) and posterior corneal central elevation (8.89 ± 11.26 μm) were significant (both P < 0.05). Corneal thickness at the center (11.11 ± 12.38 μm) and thinnest point (15.89 ± 12.75 μm) increased after treatment (all P < 0.001). Other significant changes included postoperative decreases in the keratoconus index (0.12 ± 0.06), index of height decentration (0.06 ± 0.05), index of surface variance (27.32 ± 13.08), index of vertical asymmetry (0.42 ± 0.21), index of height asymmetry (8.42 ± 20.57), and an increase in the center keratoconus index (0.01 ± 0.02) (P < 0.001).

Conclusions: This study demonstrates that ICRS implantation provides favorable mid-term outcomes in treatment of mild and moderate progressive keratoconus and can improve corneal indices compared with their preoperative states.