ABSTRACT
BackgroundIt is important to measure the corneal curvature, anterior chamber depth (ACD) and axial length accurately for calculating IOL power. The interchange outcomes from different measuring methods and apparatus will cause unreliable IOL power. ObjectiveThe present study was to compare the differences of corneal curvature, anterior chamber depth (ACD) measured by IOLMaster and Orbscan Ⅱbefore and after laser in situ keratomileusis(LASIK) and further compare the axial length measured by IOLMaster and A-ultrasound. Methods One hundred and thirty eyes from 65 consecutive myopic patients before LASIK and 56 eyes of 28 cases with 1-month follow-up duration after LASIK in Henan Eye Institute were enrolled in this study. The K value, ACD between IOLMaster and Orbscan Ⅱ as well as results of axial length between IOLMaster and A-ultrasound were compared by using paired t test. The agreements of the measured values among IOLMaster, Orbscan Ⅱ and A-ultrasound were evaluated using Bland-Altman plot. ResultsBefore LASIK,the K value measured by IOLMaster,Orbscan Ⅱ were ( 43.32 ± 1.52 ) D and ( 42.99 ± 1.45 ) D respectively with the difference value of( 0. 33 ±0. 03 ) D, showing a significant difference(t=10. 380,P=0.000) and a positive relation between them(r=0.971,P=0.000). After LASIK,the K value measured by IOLMaster, Orbscan Ⅱwere(39. 02±2. 14) D and ( 38.91 ±2. 04) D with the difference value (0. 12±0. 33 ) D, presenting a significant differences between them (t =2.715, P =0.009). Bland-Altman plots indicated the disagreement in K value and uninterchangeable. Before LASIK, the ACD measured by IOLMaster,Orbscan Ⅱ and A-ultrasound were ( 3.72 ± 0. 22 ) mm, ( 3.69 ±0. 22 ) mm and ( 3.75± 0.27 )mm respectively and no significant differences were found between them (P ＞ 0. 05 ). Axial length measured by IOLMaster significantly prolonged in comparison with A-ultrasound(25.59± 1. 01 mm vs 25.22±0.99 mm ) , and the difference was( -0. 37 ±0. 30 ) mm, showing significant difference ( t =- 14. 098, P =0. 000 ) and positive correlation ( r =0. 954, P =0. 000 ). Axial length values measured by IOLMaster were ( 25.54 ± 1.05 ) mm in preoperation and ( 25.48 ± 1.01 ) mm in postoperation with the difference (0.052±0. 412)mm, showing statistically insignificant difference between them (t=0. 946,P=0. 348). ConclusionsKeratometries measured by IOLMaster,Orbscan Ⅱ are much more different. Therefore,these two methods are not recommended to use interchangely. ACD measured by IOLMaster,Orbscan Ⅱ and A ultrasound are proved to obtain the similar results and is clinically interchange. Axial length measured by IOLMaster is longer than that measured by A-ultrasound.