Clinical outcomes of two symmetrical Kera-rings implanted in grade three keratoconus: a retrospective nonrandomized study.

Purpose: To evaluate the clinical outcomes of implanting two symmetrical Kerarings via a femtosecond laser in grade three keratoconus.

Patients and methods: This was a retrospective nonrandomized controlled clinical study. The study included one eye from each of twenty-three patients, all with Grade 3 keratoconus as classified by the Amsler-Krumeich classification. The ICRS surgery was performed with the patient under topical anaesthesia (benoxinate hydrochloride 4 mg/mL 0.4%). A tunnel channel was created by a femtosecond laser using a 60-kHz infrared neodymium glass femtosecond laser at a wavelength of 1053 nm (Abbott Laboratories Inc., Abbott Park, Illinois, USA). Two symmetrical Kerarings (Mediphacos Inc., Belo Horizonte, Brazil) were implanted in all the cases with 160° arcs and 250,300 µm thicknesses according to the corneal thickness at the implantation site. After surgery, the patients underwent a full ocular evaluation on Days 1, 7, and 14 and after one month. For a period of 1 year, corneal topography readings were taken quarterly, and the numbers of Pentacam measurements were averaged.

Results: Twenty-three eyes of twenty-three patients were included in this study. The mean value (± SD) of age was 22.8 (± 6.84) years. Six (26.09%) eyes were from males, and 17 (73.91%) were from females. The cone location was central for all patients. Spherical error, cylindrical error, spherical equivalent (SE), uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA) significantly improved after 3, 6, 9, and 12 months compared with the preoperative values (P value < 0.001). There was no significant difference in the axial and pachymetry readings before and after surgery. Kmax flattened insignificantly at 3 and 6 months of follow-up, whereas significant flattening was achieved at 9 and 12 months (P values = 0.046 and 0.042, respectively). The K mean, K1, K2, anterior elevation, topographic cylinder, and Q value posterior to the corneal surface were significantly lower at the 3-, 6-, 9- and 12-month follow-up visits than preoperatively (P value < 0.05). Posterior elevation and the Q value of the anterior corneal surface were significantly greater after surgery (3, 6, 9, and 12 months) than before surgery (P value < 0.05). With respect to the Belin ABCD grading system, A and D significantly improved throughout the follow-up visits (3, 6, 9, and 12 months) (P value < 0.001), whereas B and C did not significantly differ between the 3-, 6-, 9- and 12-month follow-up visits and the preoperative values.

Conclusion: Grade 3 KC, with the central cone managed with two symmetrical kera-rings, showed favourable results with respect to clinical and topographic outcomes, with improvements in the ABCD staging system of KC.