PURPOSE To compare the outcomes obtained with models of asymmetric and non-asymmetric intracorneal ring segments (ICRS) in keratoconic eyes with asymmetric topo-graphic patterns. METHODS In this prospective observational study, ICRS were implanted alternately in patients with the same tomographic patterns of keratoconus assigned to four groups. Patients with the "duck" phenotype received one asymmetric or non-asymmetric ICRS and patients with the "snowman" pheno-type received two asymmetric or non-asymmetric ICRS. Visual, refractive, astigmatism, keratometric, and corneal aberrometry changes were evaluated over a 6-month follow-up period. RESULTS Sixty-eight eyes were analyzed. No significant difference was observed between the use of one asymmetric and one non-asymmetric ICRS in duck phenotypes. In snowman keratoconus, the inferior-superior index decreased significantly (P = .03) with asymmetric but not with non-asymmetric ICRS implantation. Total corneal higher order aberrations and coma rates were lower, but not significantly so, after the implantation of two asymmetric ICRS in snowman phenotypes (2.85 ± 0.89 to 2.60 ± 0.91 µm, P = .20 and 2.64 ± 0.93 to 2.39 ± 0.98 µm, P = .21), and significantly higher after the implantation of two non-asymmetric ICRS (2.56 ± 1.28 to 3.08 ± 1.62 µm, P = .02 and 2.34 ± 1.27 to 2.84 ± 1.62 µm, P = .02). CONCLUSIONS Asymmetric ICRS did not improve the outcomes of ICRS implantation in duck keratoconus. However, the implantation of two asymmetric ICRS was more effective than that of two non-asymmetric ICRS for decreasing vertical asymmetry and preventing increases in corneal aberration in the snowman phenotype of keratoconus. [J Refract Surg. 2021;37(8):552-561.].

中文翻译：

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非对称与非对称基质内角膜环段治疗圆锥角膜的比较研究。

目的 比较使用不对称和非对称角膜内环段 (ICRS) 模型在具有不对称地形图案的圆锥角膜眼中获得的结果。方法 在这项前瞻性观察研究中，ICRS 交替植入具有相同圆锥角膜断层扫描模式的患者，分为四组。“鸭”表型患者接受了一种不对称或非对称 ICRS，而“雪人”表型患者接受了两种不对称或非对称 ICRS。在 6 个月的随访期内评估了视觉、屈光、散光、角膜曲率和角膜像差测量的变化。结果 分析了 68 只眼睛。在鸭表型中使用一种不对称和一种非对称 ICRS 之间没有观察到显着差异。在雪人圆锥角膜中，不对称ICRS 植入的上下指数显着降低（P = .03），但非对称ICRS 植入则没有。在雪人表型（2.85 ± 0.89 至 2.60 ± 0.91 µm，P = .20 和 2.64 ± 0.93 至 2.39 ±, 0.98 µm）中植入两个不对称 ICRS 后，总角膜高阶像差和彗差率较低，但不显着P = .21)，并且在植入两个非对称 ICRS 后显着更高（2.56 ± 1.28 至 3.08 ± 1.62 µm，P = .02 和 2.34 ± 1.27 至 2.84 ± 1.62 µm，P = .02）。结论 不对称 ICRS 没有改善鸭圆锥角膜植入 ICRS 的结果。然而，在降低垂直不对称性和防止圆锥角膜雪人表型角膜像差增加方面，植入两个不对称 ICRS 比植入两个非对称 ICRS 更有效。[J 屈光手术。2021;37(8):552-561.]。