Abstract

Aim: This study evaluates the topographic and aberrometric changes induced by ICRS in patients with moderate and severe keratoconus and analyzes pre-operative factors affecting the refractive and visual outcomes.
Methods: This retrospective, observational, nonrandomized, and single-center case series, included 21 keratoconic eyes of 21 patients implanted with Keraring ICRS (Mediphacos, Belo Horizonte, Brazil), using the manual tunnelization technique and vacuum device. All subjects were examined after 6 months following surgery, including the measurement of uncorrected visual acuity (UCVA), best-Corrected Distance Visual Acuity (CDVA), refractive data, pachymetry, corneal topography, and aberrometry.
Results: The mean age of 21 patients was 31.14±10.65 years, eleven (52%) were male. Kerarings were successfully implanted in all eyes. After 6-month from implantation, significant increase was found in mean UCVA (P<0.01) and CDVA (P<0.01). There was a statistically significant reduction in refractive cylinder (P<0.01), corneal cylinder (P=0.020), Kmax (P<0.01) and BFS (P=0.02). Statistically significant differences were found in several aberrometric parameters for 6-mm pupil, RMS HOA (P=0.045), oblique astigmatism (P=0.009), vertical coma (P=0.02), and oblique trefoil (P=0.018).
Conclusion: Analysis of the visual outcomes after Keraring ICRS implantation showed a significant postoperative corneal flattening with a subsequent increase in UCVA and CDVA. Visual, refractive, topographic and aberrometric parameters remarkably change in the 6-month period after Kerarings implantation. Kerarings in this sample have shown to provide a mild visual rehabilitation between 2 and 3 lines, particularly in more advanced cases. Furthermore, flattening of the anterior segment induced by the surgery might be beneficial for contact lens fitting.

Keywords:Keratoconus; Intrastromal corneal ring segments; Keraring; Vacuum system; K astigmatism; Spherical aberration; Coma; Corneal thickness