Impact of unintended initial dissection of the posterior plane during SMILE surgery on surgery time and visual outcomes

BACKGROUND: To study the impact of unintended initial dissection of the posterior plane (UIDPP) on operation time and surgical outcomes during small incision lenticule extraction (SMILE) surgery. METHODS: This was a retrospective study. Based on the SMILE procedure video, the operating eyes were assigned to the normal and UIDPP groups according to the presence or absence of UIDPP signals during surgery. The UIDPP group was further separated into early and late detection based on whether the complete dissection of the lenticule posterior plane or not. Patient's demographic data, preoperative evaluation data, operation time and postoperative outcomes were collected. RESULTS: Sixty-six patients (66 eyes) who underwent SMILE were included, with 24 eyes with UIDPP (13 in the early detection group and 11 in the late group). The optical zone was smaller (median 6.5 vs. 6.6, P = 0.007), and the operation time was longer (median, 189.5 vs. 91.0 s, P < 0.001) in the UIDPP group compared with normal group. There were significant differences in operation time between the late detection group and early detection group (median, 489.0 vs. 139.0 s, P < 0.05) and between the late detection group and normal group (median 489.0 vs. 91.0 s, P < 0.05), while the optical zone was different only between the late detection and normal groups (median, 6.5 vs. 6.6, P < 0.05). At the one-year follow-up, UDVA was better than or equal to 20/20 in 87.5% of eyes, and 75% of eyes were within ± 0.5 D of the intended refractive target. One eye lost one Snellen line. CONCLUSION: The occurrence of UIDPP will significantly prolong the operation time, but not affect the recovery of long-term visual acuity after surgery. Detecting UIDPP earlier could help shorten the operation time.