To compare the results of single versus double intracorneal ring segment (ICRS) (KeraRing) implantation in keratoconus with respect to different cone locations. Twenty-two eyes of 18 patients with totally asymmetric cones (20–80% or 0–100% distribution along steep axis) were implanted with single ICRS (Group 1), 38 eyes of 32 patients with central or partially asymmetric cones (50–50% or 40–60% distribution along steep axis) were implanted with double ICRS (Group 2), at a depth of 80% of the site of implantation, in channels created with femtosecond laser device. All patients had uncorrected and corrected distance visual acuities (UDVA and CDVA, respectively) of ≤ 0.3 Snellen lines. In both groups, patients had median UDVA and CDVA gain of 3 Snellen lines (P > 0.05). Postoperative improvement in indices of vertical asymmetry and height decentration in Group 1; simulated keratometry, corneal astigmatism and anterior corneal asphericity values in Group 2 were greater (P < 0.05). A total of 10 eyes (45.5%) in Group 1 were recommended double ring implantation by the manufacturer’s nomogram, but underwent single ICRS implantation and achieved visual, refractive, tomographic outcomes comparable to that in Group 2, although corneal cylindrical correction was less and final topographic astigmatism was greater. Double ICRS implantation seems to be superior in terms of keratometry, corneal astigmatism and anterior corneal asphericity improvement. Single ICRS implantation in totally asymmetric cones seems to provide satisfactory visual, refractive and tomographic results, similar to double ICRS implantation in central and partially asymmetric cones, by inducing central shift of the cone.

中文翻译：

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不对称和中心锥中角膜内环段的数量

比较不同圆锥位置在圆锥形圆锥角膜中单对角膜内环段和双角膜内环段（ICRS）（KeraRing）植入的结果。在18例完全不对称视锥（沿陡轴分布为20–80％或0–100％）的18例患者中，有22眼植入了单个ICRS（第1组），在32例中枢或部分不对称视锥（50-在飞秒激光装置产生的通道中，在植入部位80％的深度处，将50％或40–60％的沿陡轴的分布）植入了双重ICRS（第2组）。所有患者的未矫正视力和矫正远视力（分别为UDVA和CDVA）≤0.3 Snellen线。两组患者的UDVA和CDVA均值增加了3个Snellen品系（P> 0.05）。第一组的术后垂直不对称和身高偏低指标的改善；模拟角膜测量法，第2组的角膜散光和角膜前非球面度值更大（P <0.05）。根据制造商的诺模图，建议在第1组中总共10眼（45.5％）进行双环植入，但进行单次ICRS植入并获得与第2组相当的视觉，屈光和断层扫描结果，尽管角膜圆柱状矫正术较少且最终地形散光较大。在角膜曲率测定，角膜散光和角膜前非球面性改善方面，双重ICRS植入似乎更好。将ICRS完全植入不对称圆锥体中似乎可以提供令人满意的视觉，屈光和断层扫描结果，