ABSTRACT
Background The assessment of total corneal power is essential to both the prediction of intraocular lens power before cataract surgery and the diagnosis of corneal ectasia.Objective This study was to access the repeatability of corneal power measurements in post-laser assisted in-situ keratomileusis (LASIK) eyes with GalileiⅡ dual Scheimpflug analyzer.Methods In this cross-sectional study,68 eyes of 36 subjects who received LASIK surgery more than 3 months in Eye Hospital of Wenzhou Medical University were recruited from July to September in 2011.The mean preoperative spherical equivalent diopter was (-4.95±2.08) D in the subjects with the diopter range from-1.75 D to-10.00 D.The parameters of corneal power were measured by Galilei Ⅱ dual Scheimpflug analyzer,including SimK,Ka,Kp,KG and Kray.Three-time consecutive measurements were completed in every examined eye to obtain the data of SimK,Ka,Kp,KG and Kray,respectively.The coefficient of variation (CV),standard deviation (SD),Cronbach α coefficient and intra-class correlation coefficient (ICC) were calculated to evaluate the repeatability.Concordance between the different measurements was assessed using Bland-Altman agreement analysis.This study followed the Helsinki Declaration,all subjects signed informed consent.Results The CVs of three-time measured SimK,Ka,Kp,KG and Kray were 0.24％,0.28％,-0.37％,0.31％ and 0.32％,respectively,and the Cronbach α values were ＞0.9 and the ICCs were ＞0.982.The Bland-Altman analysis between different measurements showed that the maximum 95％ limits of agreement (LoA) were 0.37 D for SimK,0.46 D for Ka,0.09 D for Kp,0.45 D for KG and 0.49 D for Kray,respectively.Conclusions The Galilei Ⅱ dual Scheimpflug analyzer performed high repeatability and concordance on corneal power measurements in post-LASIK eyes.The differences between measuring results are clinically acceptable.
ABSTRACT
PURPOSE: To evaluate the relation between clinical history method and Orbscan II for corneal power measurement after laser in situ keratomileusis (LASIK). METHODS: A total of 77 consecutive eyes of 43 patients who were treated with LASIK for myopia were followed up for at least 6 months. Corneal power by clinical history methods (CK) was compared with 3.0 mm zones of simulated keratometry (Sim-K), with 0.5, 1.0, 1.5, 2.0 and 3.0 mm zones of axial power maps (AP) and with 2.0, 3.0, 3.5, 4.0 and 5.0 mm zones of total optical power maps (TOP). RESULTS: Sim-K and all AP-map zones using Orbscan II were significantly higher (P<.001) than the CK value, while all TOP-map zones were significantly lower (P<.001) than the CK value. Among them, 3.0 and 4.0 mm TOP-map zones showed the highest correlation with the corneal power by CK (r2=0.889, P<.001; r2=0.889, P<.001). The correlation was higher with 3.0 mm TOP-map zone (r2=0.800, P<.001) than with 4.0 mm TOP-map zone (r2=0.793, P<.001) in high myopia patients. CONCLUSIONS: Although 3.0 and 4.0 mm TOP-map zones of Orbscan II were correlated highly with the CK value, these correlations were relatively low in high myopia patients and 3.0 mm TOP-map zone was better correlated than 4.0 mm TOP-map zone in these patients.