Possible Risk Factors and Clinical Effects of Opaque Bubble Layer in Small Incision Lenticule Extraction (SMILE)

To report the development of an opaque bubble layer (OBL) during small incision lenticule extraction (SMILE) and analyze its potential risk factors and the clinical outcome.A retrospective review of medical records was performed. The patients were divided into two groups in terms of OBL area following a posterior lenticule cut: OBL less than 5% of cornea and OBL greater than 5% of cornea. Preoperative parameters and clinical outcomes were compared. The association between amount of OBL and the various parameters was determined using a correlation analysis.The study included 208 myopic eyes (106 patients). The incidence of OBL was 51.82% (108 eyes) and mean OBL area was 3.06% ± 4.62%. The OBL greater than 5% group (48 eyes, 23.08%) had a thicker cornea, a thinner lenticule, and a longer operation time than the OBL less than 5% group (160 eyes, 72.92%). Visual acuity, efficacy, and safety were similar between groups except for a slightly lower predictability value for the OBL greater than 5% group. The amount of OBL area presented a quantitative association with corneal thickness, lenticule thickness, and the relative vertical position of the posterior lenticular surface. Flap tear was observed in 8 eyes (3.84%), at which an extensive amount of OBL (9.76% ± 7.02%) developed.Eyes with a thicker cornea or a thinner lenticule are more likely to develop OBL during SMILE. The OBL does not affect the overall clinical outcome. In eyes with extensive OBL, there is a higher incidence of flap tear and a lower predictability value. [J Refract Surg. 2017;33(1):24-29.].