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

PURPOSE: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.].