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Updated: Sep 2, 2025
Three Different Protocols of Corneal Collagen Crosslinking in Keratoconus: Conventional, Accelerated and Iontophoresis
Published on: November 12, 2015
Clinical, tomographic, and topometric outcomes of progressive thickness intracorneal ring segment implantations in
Efekan Coskunseven1, Belma Kayhan2
1Department of Refractive Surgery, Dunyagoz Etiler Hospital; Faculty of Health Sciences, Istanbul Rumeli University, Istanbul, Turkey.
Purpose:
To evaluate the visual, refractive, tomographic, and topometric outcomes of progressive thickness intracorneal ring segment (PT-ICRS) implantation in duck-type keratoconus.
Methods:
This retrospective study included eyes with oval (duck-type) keratoconus treated with PT-ICRS implantation. After the femtosecond laser tunnel creation, one PT-ICRS (Keraring AS 5 with 160° arc length) was implanted along the ectatic, inferior half of the cornea. Data of uncorrected and corrected distance visual acuity (UDVA and CDVA), refraction, asphericity (Q value), and keratometry (K) were compared pre- and postoperatively. Additionally, changes in the topometric indices of corneal irregularity were also evaluated after PT-ICRS implantation.
Results:
Thirty-one eyes of 30 patients were included in the study with a mean follow-up time of 9.06 months (ranging between 6 and 18 months). UDVA improved from 0.85 ± 0.36 to 0.27 ± 0.14 logMAR (P = 0.001), and CDVA improved from 0.37 ± 0.22 to 0.13 ± 0.11 logMAR (P = 0.001). The mean spherical error decreased from -3.66 ± 2.60 to -1.60 ± 1.42 D (P = 0.001), and the mean cylindrical error decreased from -4.91 ± 2.65 to - 1.41 ± 1.31 D (P = 0.001). All topographic parameters measured from the anterior cornea demonstrated statistically significant improvements after PT-ICRS implantation (P = 0.001). K mean, K maximum, corneal astigmatism, and Q value showed a significant decrease. Besides the index of height asymmetry, all topometric indices were significantly reduced after PT-ICRS implantation. There were no loss of lines and no complications.
Conclusion:
PT-ICRS implantation in duck-type keratoconus is an effective and safe treatment. This intervention improves the visual acuity, refractive error, topographical, and topometric parameters significantly by decreasing both eccentricity and steepness of the cone.
