混合性散光四种手术设计模式的相互转换和手术参数比较

目的 初步探讨LASIK手术矫正混合性散光四种设计模式的转换公式和手术参数对比情况,以便加深对混合性散光设计模式的理解和掌握.方法 随机选取行LASIK手术的混合性散光病例10例(13只眼),寻找四种设计模式之间的转换公式,并对四种设计模式的理论切削厚度、剩余基质床厚度和激光脉冲数分别进行配对t检验.结果 转换公式:如果负柱镜法用(a)DS/(b)DCx(c)表示,则正柱镜法可表示为(a+b)DS/(-b)DC×(90+c)或(c-90),两光区交叉柱镜法可表示为(a+b)DC×(c),(a)DC×(90+c)或(c-90),三光区交叉柱镜法可表示为(b/2)DC×(c),(-b/2)DC×(90+c)或(c-90),(a+b/2)DS.就手术参数而言,两光区交叉柱镜法在理论切削厚度、激光脉冲数和剩余基质床厚度方面都具有绝对优势,三光区交叉柱镜法和负柱镜法居中,二者差异无统计学意义,而正柱镜法则最消耗角膜组织和激光切削时间最长.结论 混合性散光的四种设计模式可以运用简单的公式进行转换,各种设计模式消耗的角膜组织都不多,如何让切削面更平坦光滑和提高术后视觉质量显得更为重要.

The transformation formulae and operation parameters of four design patterns to correct mixed astigmatism

Objective To discuss the transformation formulae and operation parameters of laser in situ kemtomileusis (LASIK)with four design patterns to correct mixed astigmatism in order to understand and master the design patterns of mixed astigmatism better.Methods This study included 13 eyes of 10 patients with mixed astigmatism treated by LASIK.We studied the transformation formulae and compared the ablation depth,residual stromal thickness,laser pulses of four design patterns.Results If the negative cylinder expressed by (a)DS/(b)DC×(c), then the positive cylinder could express by (a+b)DS/(-b )DC×(90+c)or (c-90),the two-zone-cross-cylinder by (a+b)DC×(c)/ (a)DC×(90+c)or (c-90),the three-zone-cross-cylinder by (b/2)DC×(c)/ (-b/2)DC×(90+c)or (c-90)/ (a+b/2)DS.For the operation parameters,the two-zone-cross- cylinder had absolute advantage at the ablation depth,residual stromal thickness and laser pulses.The three-zone-cross-cylinder and negative cylinder were placed in the middle, and there had no statistical difference between them.The most corneal tissue was ablated in positive cylinder pattem.Cunclusion The four design patterns of mixed astigmatism could transform by simple formulae.A little corneal tissue was ablated to correct mixed astigmatism with each design pattern,and it was more important how to smoothen the interface and improve the vision quality.