Preussner P-R, Hoffmann P, Petermeier K
Universitätsaugenklinik Mainz, Langenbeckstrasse 1, Mainz.
Klin Monbl Augenheilkd. 2009 Feb;226(2):83-9. doi: 10.1055/s-2008-1027966. Epub 2009 Feb 10.
The aim of this study was to compare the different calculation methods in large patient collectives, including eyes with extreme axial lengths.
The prediction errors of the Haigis, SRK/T, Hoffer-Q and Holladay formulae and of the OKULIX ray-tracing are compared in 2888 normal eyes implanted with 8 IOL models. The 5 methods are adjusted to zero mean prediction error for each subcolletive implanted with a particular IOL model, in the formulae by variation of the "formula constants" and in the ray-tracing by adjusting the mean anterior chamber depth. 249 short eyes (mean axial length 21.3 mm) are than compared with the same adjusting parameters. Two collectives from two hospitals with very long eyes (59 eyes with mean axial length of 30.4 mm and 50 eyes with mean axial length of 31.4 mm) and two extremely short eyes (16.7 mm and 16.72 mm) of the same patient are additionally included into the investigation.
In normal eyes, standard deviations of the mean prediction errors ( approximately 0.59 D), mean absolute errors approximately 0.43 D) and median of the absolute error approximately 0.33 D) do not differ between the five methods. The differences increase with the distance from "normal" eyes and are up to 6 D in the extremely short ones.
As long as only axial lengths and corneal radii are used as input parameters, the choice of the calculation method appears not to be relevant in the case of normal eyes, because other errors are dominant. Other than the formulae, the ray-tracing method can be applied to non-normal eyes (extremely short or long ones) without bias induced by the calculation method. In particular, additionally measured data such as topography or spatially resolved corneal thickness can be used, e. g., in eyes after refractive surgery.
本研究的目的是比较在大量患者群体中，包括眼轴长度极长的眼睛在内的不同计算方法。
比较了Haigis、SRK/T、Hoffer-Q和Holladay公式以及OKULIX光线追踪法在植入8种人工晶状体模型的2888只正常眼中的预测误差。对于每种植入特定人工晶状体模型的子群体，通过改变“公式常数”来调整公式中的5种方法，使其平均预测误差为零；在光线追踪法中，通过调整平均前房深度来实现。然后将249只短眼（平均眼轴长度21.3毫米）与相同的调整参数进行比较。另外，来自两家医院的两个眼轴长度极长的群体（59只平均眼轴长度为30.4毫米的眼睛和50只平均眼轴长度为31.4毫米的眼睛）以及同一患者的两只极短眼（16.7毫米和16.72毫米）也被纳入研究。
在正常眼中，五种方法之间的平均预测误差标准差（约0.59 D）、平均绝对误差（约0.43 D）和绝对误差中位数（约0.33 D）没有差异。差异随着与“正常”眼距离的增加而增大，在极短眼中可达6 D。
只要仅将眼轴长度和角膜半径用作输入参数，在正常眼的情况下，计算方法的选择似乎并不重要，因为其他误差占主导地位。除了公式外，光线追踪法可应用于非正常眼（极短或极长眼），而不会因计算方法产生偏差。特别是，额外测量的数据，如地形图或空间分辨的角膜厚度，可用于例如屈光手术后的眼睛。
