Intrastromal corneal ring segment implantation for the treatment of keratoconus

To evaluate the safety and efficacy of intrastromal corneal ring segment implantation using both mechanical and femtosecond-assisted tunnel creation for the treatment of patients with keratoconus.

A retrospective noncomparative interventional study including 96 eyes of 75 patients with keratoconus. All patients had contact lens intolerance and clear central corneas. Corneal tunnels were made using a femtosecond laser in 26 eyes (femtosecond group) and mechanically in 70 eyes (mechanical group). The Keraring (Mediphacos, Belo Horizonte, Brazil) was implanted in each eye, and a complete ophthalmic examination was performed, including visual acuity, refraction, and keratometric readings.

The mean preoperative uncorrected visual acuity for all eyes was 1.40 ± 0.39 logarithm of the minimal angle of resolution (logMAR) (mean ± SD) and improved to 0.60 ± 0.34 logMAR at the sixth month (n = 96, P < 0.001) and 0.50 ± 0.32 (n = 54, P < 0.001) at the 18th month. The mean preoperative best spectacle-corrected visual acuity (BSCVA) for all eyes (n = 96) was 0.68 ± 0.36 logMAR. The mean BSCVA was 0.29 ± 0.21 (n = 96, P < 0.001) at the sixth month and improved to 0.26 ± 0.20 (n = 54, P < 0.001) at the 18th month. There was a significant reduction in spherical equivalent refractive error from -5.88 ± 3.65 diopters (D) (n = 96) to -2.26 ± 1.98 D (n = 54, P < 0.001) at the 18th month. The mean preoperative maximum keratometry (Kmax) was 53.58 ± 5.90 D and decreased to 49.02 ± 4.70 (n = 96, P < 0.001) at 6 months and 48.57 ± 4.36 D (n = 54, P < 0.001) at the 18th month. Sixth month results of the mechanical versus femtosecond groups were as follows: improvement in uncorrected visual acuity (2.08 vs. 1.50 lines), improvement in BSCVA (2.93 vs. 2.19), reduction in spherical equivalent (3.78 vs. 3.75 D), and reduction in maximum keratometry (4.66 vs. 4.62 D). There was no statistically significant difference between both groups for any parameter.

Keraring implantation is effective for the treatment of keratoconus, providing safety and good visual outcomes after both mechanical and femtosecond-assisted tunnel creation.