Femtosecond-assisted intrastromal corneal single-segment ring implantation in patients with keratoconus: a 12-month follow-up.

Objective: To determine visual rehabilitation in patients with keratoconus who received femtosecond-assisted intrastromal corneal single-segment ring implantation.

Methods: This prospective study was conducted on 62 eyes of 45 patients with keratoconus who received single-segment Intacs. The FS200 femtosecond laser was used for tunnel creation. Patients were examined for astigmatism, uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and manifest refraction spherical equivalent (MRSE) before the operation and 1, 6, and 12 months after operation. Scheimpflug imaging including minimum keratometry reading (min-K), maximum keratometry reading (max-K), average of minimum and maximum keratometry readings (mean-K), central corneal thickness (CCT), asphericity (Q-value), index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), center keratoconus index (CKI), index of height asymmetry (IHA), index of height decentration (IHD), and minimum sagittal curvature (Rmin) was performed before and 12 months after the operation.

Results: The mean preoperative UCVA was 20/130, which increased to 20/62 1 year after the operation (P < 0.001). The mean BCVA in the last follow-up was 20/32, which improved when compared with preoperative BCVA (20/40) (P = 0.008). One year after the operation, MRSE and cylinder decreased to 1.33 ± 1.90 diopter (D) and 0.46 ± 1.50 D, respectively (P < 0.001 for both). Min-K, max-k, and mean-k reduced to 1.67 ± 0.1.40 D, 2.08 ± 1.84 D, and 1.85 ± 1.30 D (P < 0.001 for all). Q-value decreased to 0.81 ± 1.14 (P < 0.001). In contrast, CKI had a significant increase of 0.02 (P = 0.002). Other evaluated indexes did not show any significant differences.

Conclusions: Implantation of the single-segment ring in patients with keratoconus improved vision because of regularizing the cornea and centralization of the corneal cone.