The Comparison Of Five Kinds Of Intraocular Lens Measurement Formulas To Predict Postoperative Refraction Accuracy

Objective: By comparing the five kinds of intraocular lens(IOL) measurementformula (SRK-Ⅱ,SRK-T, Holladay, Hoffer-Q, Haigis) to predict the degree of accuracyof intraocular lens in different axial length, the reference before cataract surgery selectthe accurate measurement of IOL formulas and predict the appropriate refraction.Methods:80eyes from the59age-related cataract patients in our hospital wereused in this study. The A-type ultrasound was used to measure axial length,80eyeswith cataract were divide into four goups according to the axial lenghs:L≤22mm,22.0mm<L≤24.5mm,24.5mm<L≤27mm,L>27mm.We used the five kinds of IOLformulas to measure their prediction of postoperative refraction, reserve the right IOLrefractive power, impalnt certain IOL.The actual postoperative refraction was measuredwith the methods of computer and retinoscopy optometry when patients could gain bestcorrected visual acuity (BCVA) in one week, one month and three months after surgeryor later. We calculated the absolute values of refractive error(AE). The t-test in twogroups was used to determine the refractive state stabilization time in one week, onemonth and three months after surgery or later.Variance analysis in two groups was usedto predict the degree of accuracy of IOL in each axial length.The t-test was used toanalysis refractive change of each axial group in one week and one month after cataract surgery.Pearson correlation analysis was used to compare the relationship of AE and theaxial length.Result: Through the analysis of the statistical t-test we find that the difference wasstatistically significant between one week and one month, one week and three monthsafter surgery(P<0.05), but no statistical significance can be considered the differencesbetween one month and three months(P>0.05).Compared with the other four formuars,the AE of the SRK-Ⅱis different in each axial length group and the differentce wasstatistically significant (P <0.05). In short axial length group, the AE of the SRK-ⅡandSRK-T formula was no significant difference.Except the short axial length group,nosignificant difference between the AE of the SRK-Ⅱand SRK-T, Holladay, Hoffer-Q,and the Haigis formula in other groups(P>0.05).SRK-T and Haigis formulas showedbetter predictability in the much longer group.In the normal and long axial lengthgroups no significant difference between the AE of the SRK-T, Holladay, Hoffer-Q, andthe Haigis formula(P>0.05),Compared with one week after surgery, the refractive statusof one month is patial myopia in short axial length group while three months is patialhyperopia in much longer group. Except the SRK-Ⅱformula,the AE of the remainingfour formulas was positively correlation with axial length (R=0.347、0.289、0.315、0.420,P <0.05).Conclusion:1.The results of this study shows that the refractive status wasbasically stable in one month after cataract surgery.2.In the sample size of the study,SRK-Ⅱand SRK-T formula have higher accuracy in predicting short axial length group,SRK-Ⅱhas more prediction error in other groups. In the normal and long axial length groups, prediction accuracy has no difference in the rest of the four kinds offormulas,but SRK-T, Holladay, Hoffer-Q formula prediction error is smaller. In themuch longer axial length group, SRK-T and Haigis formula showed a betterpredictabilly.3.Compared with one week and one month after surgury,short axial groupshowed myopia drift while much longer axial group showed hyperopia drift. Apart fromSRK-Ⅱ formula,AE and axial length was positively correlated in the remaining fourformulas.