Asymmetric intracorneal ring segments in the treatment of snowman phenotype keratoconus

Abstract

Objective: To evaluate refractive, aberrometric, topographic, and topometric outcomes of asymmetric intracorneal ring segment (ICRS) implantation in snowman phenotype (asymmetric bow-tie) keratoconus.

Methods: This retrospective, interventional study included eyes with snowman phenotype keratoconus. Two asymmetric ICRSs (Keraring AS) were implanted after femtosecond laser-assisted tunnel formation. Visual, refractive, aberrometric, topographic, and topometric changes after asymmetric ICRS implantation were evaluated with a mean follow-up of 11 months (6-24 months).

Main results: Seventy-one eyes were analyzed in the study. Keraring AS implantation corrected refractive errors significantly. The mean spherical error decreased from -5.06±4.23 D to -1.62±3.45 D (P=0.001), and the mean cylindrical error decreased from -5.43±2.48 D to -2.44±1.49 D (P=0.001). Uncorrected distance visual acuity improved from 0.98±0.80 to 0.46±0.46 Log MAR (P=0.001), and corrected distance visual acuity improved from 0.58±0.56 to 0.17±0.39 Log MAR (P=0.001). Keratometry (K) maximum, K1, K2, K mean, astigmatism, and corneal asphericity (Q-value) showed a significant decrease (P=0.001). Vertical coma aberration decreased significantly from -3.31±2.12μm to -2.56±1.94μm (P=0.001). All topometric indices of corneal irregularities were significantly reduced postoperatively (P=0.001).

Conclusions: Keraring AS implantation in snowman phenotype keratoconus demonstrated good efficacy and safety. Clinical, topographic, topometric, and aberrometric parameters improved significantly after Keraring AS implantation.

Keywords: Anneau intracornéen; Astigmatism; Astigmatisme; Asymmetric bow-tie; Chirurgie réfractive; ICRS; Intracorneal ring; Keratoconus; Kératocône; Nœud papillon asymétrique; Phénotype bonhomme de neige; Refractive surgery; SAIC; Snowman phenotype.