Anterior Segment Changes After Femtosecond Laser-Assisted Implantation of a 355-Degree Intrastromal Corneal Ring Segment in Advanced Keratoconus

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Purpose:To study anterior segment changes after implantation of a Keraring with a 355-degree arc length in central advanced keratoconus.Methods:Thirty eyes of 22 patients with advanced central keratoconus (grade 3) and absent corneal scarring underwent femtosecond laser-assisted (VisuMax) implantation of a Keraring 355-degree arc length intrastromal corneal ring segment (ICRS) with a segment thickness of 300 μm. Comprehensive ocular evaluations were performed preoperatively and postoperatively to assess uncorrected distance visual acuity, corrected distance visual acuity, K1, K2, Kmax, corneal volume, anterior chamber depth, corneal elevations, and actual segment position 6 months after the procedure.Results:Corrected distance visual acuity in decimal notation improved significantly from 0.22 ± 0.17 to 0.49 ± 0.22 (P < 0.01). Statistically significant changes were found in the measured parameters with marked reconstruction of the cornea and anterior chamber. However, the actual depth percent of the ring segment was 61.7% ± 5.9%, which was shallower than the intended depth of 80% of corneal thickness.Conclusions:These findings may help explain the marked improvement in visual parameters obtained from the Keraring 355 degrees in advanced central keratoconus. In addition, these types of rings may be a safe, effective, and minimally invasive way to avoid corneal grafting in advanced keratoconus with a clear cornea.

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