Repeatability and accuracy of corneal parameters in post-LASIK eyes measured by Fourier-domain optical coherence topography

Abstract

Objective To evaluate the repeatability and accuracy of corneal parameters in post-laser in situ keratomileusis (LASIK) eyes obtained by RTVue Fourier-domain optical coherence topography (FD-OCT).Methods In this prospective study,58 right eyes of 58 persons who agreed to undergo LASIK were included.Subjective refractions were performed before LASIK and 3 months after LASIK.IOL Master was used to evaluate corneal power before LASIK.Three months after LASIK,RTVue FD-OCT was used to evaluate the anterior corneal curvature in a 3 mm central zone (Ranterior),posterior corneal curvature in a 3 mm zone (Rposterior),the ratio of posterior and anterior curvature (Rposterior/Ranterior),central corneal thickness (CCT),total corneal power (Knet),simulated corneal power (SimK),anterior corneal power (Kanterior),and posterior corneal power (Kposterior).Km was obtained with IOL Master 3 months after the surgery.Kchm was calculated from the patient's clinical history.Repeatability of corneal parameters was assessed using the coefficient of variation (CV),Cronbach's alpha,and intra-class correlation coefficient (ICC).Bonferroni corrected multiple comparisons analyzed the differences between SimK,Knet,Km and Kchm.A Pearson correlation analyzed the correlations between SimK,Knet,Km and Kchm.Bland-Altman plots analyzed the agreements between SimK and Kchm,Knet and Kchm,Km and Kchm,SimK and Knet,and SimK and Km.Results The Ranterior,Rposterior,Rposterior/Ranterior,Kanterior,Kposterior,SimK,Knet and CCT were (8.560±0.292)mm,(6.525±0.159)mm,0.763±0.024,(43.98±1.48)D,(-6.13±0.15)D,(39.47±1.33)D,(37.93±1.42)D and (451.81±33.91)μm,respectively.The CVs of all parameters were lower than 1％.Cronbach's alpha and ICC were both higher than 0.9.SimK was (0.434±0.433)D higher than Kchm Knet was (1.112±0.471)D lower than Kchm,Km was (0.334±0.379)D higher than Kchm,and SimK was (1.546±0.162)D higher than Kchm.All the differences were statistically significant (P＜0.01).SimK was (0.100±0.287)D higher than Km but the difference was not statistically significant.There were close correlations among SimK,Knet,Km and Kchm (r≥0.944,P＜0.01).The Bland-Altman analysis showed that the 95％ limit of agreements between SimK and Kchm,Knet and Kchm,Km and Kchm,SimK and Knet,and SimK and Km were-0.41～1.28 D,-2.04～-1.11 D,-0.41～1.08 D,1.23～1.86 D,-0.46～0.66 D,respectively.Conclusion The RTVue Fourier-domain OCT had high repeatability on corneal curvature and CCT measurements in post-LASIK eyes.The SimK obtained by RTVue Fourier-domain OCT and IOL Master were 0.3 to 0.4 D higher than those obtained by clinical history.Knet may be a more accurate method to assess corneal power in post-LASIK eyes,but further clinical studies are needed for the prediction of post-LASIK intraocular lens power. Key words: Tomography,optical coherence; Keratomileusis,laser in situ; Corneal curvature; Corneal thickness; Repeatability; Agreement