Comparison of Intraoperative Ultrasound Pachymetry and Postoperative Optical Coherence Tomography of

Purpose:To compare the measurement of flap thickness using intraoperative ultrasound pachymetry and postoperative visante anterior segment optical coherence tomography (VisanteOCT) in eyes receiving laser in situ keratomileusis (LASIK).Methods:Seventeen patients (34 eyes) received LASIK using a Technolas-217Z100 laser and AMADEUS Ⅱ mechanical microkeratome (140 μm head). Flap thickness was assessed with an ultrasound pachymeter intraoperatively and a Visante - OCT postoperatively at 1week and 1month.Results:The intraoperative mean flap thickness by ultrasound pachymetry was (124±13.9) μm (range:96.5 to 160 μm),and mean flap thickness by Visante-OCT was (145±7.13) μm (range:130 to 158 μm) and (143±5.32) μm (range:132 to 155 μm) postoperatively at 1week and 1month respectively (F=63.52,P＜0.01).Intraoperative subtraction pachymetry underestimated flap thickness compared with postoperative Visante-OCT (P＜0.01).There was no significant difference between postoperative Visante-OCT measurements at 1week and 1month after LASIK (P=0.16).The 95％ limit of agreement (LoA)of flap thickness between ultrasound VisanteOCT and pachymetry was -5.40 to 42.10 μm.Conclusion:OCT overestimates flap thickness compared with intraoperative ultrasound pachymetry when using the AMADEUS Ⅱ mechanical microkeratome.(Eye Science 2012;27:60-63)