Gas Bubble Escape Sign: A New Intraoperative Sign to Predict Immediate Visual Quality After Small Incision Lenticule Extraction.

Abstract

To describe a new intraoperative sign called the "gas bubble escape" (GBE) sign to predict the ease of dissection and immediate postoperative quality of vision after small incision lenticule extraction (SMILE). The term GBE sign refers to the escape of gas bubbles followed by an immediate clarity of the interface on delineation of the lenticule planes in SMILE. This sign may indicate an optimized laser energy, which may facilitate an easy dissection of lenticule, potentially resulting in good quality of vision immediately postoperatively. This prospective study included 100 eyes of 50 patients undergoing bilateral myopic SMILE, wherein a randomly selected 32 (29 patients) of 68 eyes showing the GBE sign intraoperatively were compared with 32 eyes (20 patients) that did not show this sign. A single surgeon performed all surgeries using the same technique and energy parameters (150 nJ energy, 4.5 µm spot spacing). At postoperative 1 day and 1 month, uncorrected distance visual acuity (UDVA), Objective Scatter Index (OSI) score, and modulation transfer function (MTF) cut-off were compared between the two groups using a double-pass system. On day 1, the mean OSI score was significantly lower (0.78 ± 0.32) in the GBE group compared to the no GBE group (1.11 ± 0.90) (P = .03). The mean UDVA was also significantly better in the GBE group (P = .001). MTF cut-off was comparable between both groups. However, at 1 month all of the above parameters were comparable between the two study groups (P > .05). The gas bubble escape sign may be a useful indicator of energy optimization, potentially resulting in good visual outcomes in the immediate postoperative period following SMILE. [J Refract Surg. 2019;35(7):467-472.].