不同晶状体屈光力计算公式在儿童屈光发育档案中的应用比较

Compare the accuracy of different methods to estimate human lens power in the refractive development of children

目的 比较在缺乏晶状体厚度时,不同晶状体屈光力计算公式的一致性,寻找简化晶状体屈光力流行病学调查的计算公式.方法 横断面研究.晶状体屈光力通过3种不同的公式计算得出.计算公式包括需要晶状体厚度值的Bennett公式,以及不需要晶状体厚度值的修正Stenstr（o）m公式及Bennett-Rabbetts公式.共189名（378眼）7～14岁正视青少年纳入研究,将测量所得的生物学数据代人上述各公式中,以Bennett公式计算所得的晶状体屈光力（PL,Bennett）作为基础值,比较另2种公式计算值（PL.Sten、PL,BR）的准确性.对相关数据进行配对符号检验、Wilcoxon秩和检验及Pearson相关分析.结果 分别应用Gullstrand-Emsley与Bennett-Rabbetts模型眼计算,发现PL,Sten[（0.46±0.35）D]较PL,BL.Bennett [（0.29±0.35）D]低,差异有显著统计学意义（Z=-159.5、-120.0,P＜0.01）.PL,BR[（0.27±0.35）D]较PL,Bennett [（0.09±0.34）D]低（Z=-112.5、-42.0,P＜0.01）.通过修正c常数使PL,BR与PL,Bennett之间差异无统计学意义（Z=5.0,P＞0.05）,两者之间的最大差异仅为1.35 D,同时85.4％的PL,BR与PL,Bennett的误差小于0.50 D.将不同年龄组PL,Bennett与PL,BR（修正c常数后）的差值进行多组Wilcoxon秩和检验（X2=314.53,P＜0.01）,2种公式计算值之间的差异在7～12岁之间逐渐减小,12岁之后差异增大.2种方法所计算得出的晶状体屈光力之间的差值与年龄呈显著负相关（r=-0.36,P＜0.01）.结论 通过c常数的修正,Bennett-Rabbetts 公式与Bennett公式所得晶状体计算值在正视青少年中表现出较好的一致性.

Objective To compare the accuracy of different methods for calculating human lens power when lens thickness is not available and find suitable methods for large-scale studies of refractive development.Methods In this cross-sectional survey,lens power was calculated by three different methods.The three methods used the biometry and refraction data of 378 emmetropic eyes of 189 subjects （age range,7-14 years）.These three methods consist of the Bennett method,which uses lens thickness,and a modification of the Stenstr（o）m method and the Bennett-Rabbetts method,both of which do not require knowledge of lens thickness.Lens powers calculated with the modifiedStenstr（o）m and Bennett-Rabbetts methods were compared for accuracy to those calculated with the Bennett method.Data were analyzed by a paired sign test,Wilcoxon rank sum test and Pearson correlation analysis.Results Using the Gullstrand-Emsley and Bennett-Rabbetts eye models,the modified-Stenstr（o）m method gave lens powers that were approximately 0.46＆#177;0.35 D and 0.29＆#177;0.35 D lower than the Bennett lens powers and were significantly different from it （signrank=-159.5,-120,P〈0.01）.The Bennett-Rabbetts method gave lens powers that were approximately 0.27＆#177;0.35 D and 0.09＆#177;0.34 D lower and were significantly different from the Bennett lens powers （signrank=-112.5,-42,P〈0.01）.By customizing the c constants,the differences in the two methods were remarkably reduced to nonsignificance （signrank=5,P〉0.05）.The largest difference was just 1.35 D.Agreement with the Bennett method was within ＆#177;0.50 D for 85.4% of the eyes.The lens power differences determined with the Bennett and Bennett-Rabbetts methods decreased with age for children 7-12 years old and increased with age for children above 12 years old （x2=314.53,P〈0.01）.The power difference between the two methods had a negative correlation with age （r=-0.36,P〈0.01）.Conclusion With appropriately customized constants,the Bennett-Rabbetts method provides a good approximation of the Bennett lens power in emmetropic eyes.However,the agreement between the two methods for myopia and hyperopia needs further study.