Relationship of Location Between Tear Film Center and Corneal Vertex Following Small-Incision Lenticule Extraction

INTRODUCTION: We aimed to measure the relationship of location between the tear film center (TFC) and corneal vertex (CV) following small incision lenticule extraction (SMILE). METHODS: A total of 100 consecutive patients (100 eyes) who underwent the SMILE procedure were included. Screen captures of intraoperative videos and pupillary offset were analyzed. Location was compared using a vector plot for the two reference points. RESULTS: The arithmetic values for the distance from the pupil center (PC) were almost identical between the TFC and CV (P = 0.118). The intraclass correlation coefficient (ICC) for the measures of distance from the CV and TFC to the PC was 0.659. The mean vector and standard deviation ellipse showed similar directional tendencies for both reference points. No significant difference was observed in the arithmetic values of decentration from the TFC and from the CV (P = 0.056). The ICC for the measures of decentration from the TFC and from the CV was 0.768. The difference in the distance from the PC was significant for the tear film mark (TFM) decentration group (P = 0.002, ICC = .480), while the difference in decentration was significant for the TFM centration group (P = 0 .000, ICC = 0.230). CONCLUSIONS: The location of the CV in each eye could be simulated by the TFC. Furthermore, TFM decentered displacement could indicate optical zone decentered displacement.