Comparison of anterior segment measuring parameters in myopia after laser in situ keratomileusis between Sirius and Pentacam / 中华实验眼科杂志

ABSTRACT

Background Sirius system,a new Scheimpflug camera combined with Placido topography,improved the capability of imaging the anterior eye segment significantly.However,the study of assessing the repeatability and agreement between Sirius and Pentacam is still lack up to now.Objective This study was to evaluate the repeatability and agreement of the anterior ocular segment measuring parameters by Sirius and Pentacam in myopia received laser in situ keratomileusis (LASIK).Methods Thirty-five myopic eyes of 35 patients received LASIK were included in School of Optometry and Ophthalmology Eye Hospital from 2010 May through 2010 July.Corneal power flat keratometry (Kf),step keratometry (Ks),mean keratometry (Km),thinnest corneal thickness(TCT),the location of TCT,anterior chamber depth (ACD) and anterior chamber volume (ACV) were measured by Sirius and Pentacam in all the eyes,respectively.The repeatability of the measuring results were evaluated using intraclass correlation coefficients (ICC) and Cronbach's coefficient alpha (CoA),and the agreement of measuring parameters between Sirius and Pentacam was analyzed using Bland-Altman plot.Results Both Sirius and Pentacam demonstrated high intraobserver repeatability,with all ICC and CoA more than 0.90.No significant differences were found in Kf values and Ks values between the two methods (t =-1.533,-1.750,P＞0.05).Km value was (39.14 ± 1.95) D by Sirius measurement,which was sígnificantly higher than (39.05 ± 1.91) D by Pentacam measurement (t =3.572,P =0.001).The TCT was (457.6 ± 40.9) μm by Sirius method,showing a significant reduce in comparison with (465.4±37.5) μm of Pentacam method (t =-6.689,P＜0.001).A positive correlation was seen in the TCT between the two methods (r=0.988,P＜0.001).The Bland-Alrman plots showed the 95％ CI-21 μm to 6 pm in the TCT value between the two devices.Pairwise comparison of the location of TCT measurements showed significant differences between the two devices (t =-4.132,-5.696,P＜0.001),with a good correlation (r=0.751,0.775) and the 95％ CI (-0.36-0.17 mm,-0.35-0.12 mm).A very good agreement was seen in ACD between the two devices (-0.02-0.12 mm),but the agreement result was not very well in the ACV between the two devices with the 95％ CI (-27.70-6.20 mm3).Conclusions Sirius and Pentacam measurements for anterior ocular segment parameters have a very good repeatability in post-LASIK eyes.In addition,good agreement results are exhibited in corneal power,TCT and ACD between Sirius and Pentacam with an acceptable maximal different value between them.Sirius and Pentacam can be used interchangeably in clinical examination.However,the two devices can not interchangeably for ACV measurement and TCT location.