Asymmetric intracorneal ring segments in the treatment of snowman phenotype keratoconus

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

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).

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).

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