Objective: To study the types, related factors and clinical significance of opaque bubble layer (OBL) produced by Visumax femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Methods:A total of 154 patients (300 eyes) who underwent FS-LASIK in the Affiliated Eye Hospital of Nanjing Medical University from July 1, 2016 to August 20, 2016 were analyzed retrospectively. Eighty-seven males and 67 females were included, with an equivalent spherical refractive error of -5.88±1.51 D. A Zeiss Visumax was used for the surgery. The OBL created during surgery were classified into three categories,including OBL outside flap, rapid OBL within flap, and slow OBL within flap. Three hundred eyes were divided into three groups based on the average K value of the corneal curvature: Group A (<42 D), Group B (42-46 D) and Group C (>46 D); On the basis of the thickness of the corneal flap: Group D (100 μm),Group E (110 μm) and Group F (120 μm); and corneal thickness: Group G (<500 μm), Group H (500-540 μm)and Group I (> 540 μm). The composition ratio of the 3 types of OBL was calculated on the basis of corneal curvature, corneal flap thickness and corneal thickness, and a multiple logistic regression model was used for statistical analysis. Results: All 300 eyes developed OBL. With the OBL outside flap as a reference,the thinner the corneal flap was, the easier the rapid OBL within flap developed (r=-0.719, P=0.034) and the easier the slow OBL within flap developed (r=-0.875, P=0.044). With the slow OBL within flap as a reference, the higher the corneal curvature was, the easier the rapid OBL within flap developed (r=0.923,P=0.046); a thicker corneal flap had a greater tendency to develop an OBL outside flap (r=0.897, P=0.044).Conclusions: There is a specific correlation between the generation of OBL and corneal curvature, corneal flap thickness, and corneal thickness. The visual quality and long-term effect influenced by the three types of OBL produced by Visumax FS-LASIK need further study.