AIM: To evaluate the effect of background diseases and number of previous intravitreal aflibercept injections (IVAIs) on immediate intraocular pressure (IOP) increase and vitreous reflux (VR) rate and to evaluate the correlation of both age and axial length with immediate IOP increase and VR rate. METHODS: This study included 105 patients with cystoid macular edema secondary to retinal vein occlusion, 35 patients with diabetic macular edema, 69 patients with neovascular age-related macular degeneration (nAMD), and 12 patients with myopic choroidal neovascularization, which underwent first-time IVAI. The correlation of immediate IOP increase and VR rates with the four background diseases was investigated. Moreover, the correlation of age with immediate IOP increase and VR rate as well as correlation of axial length with immediate IOP increase and VR rate were evaluated. Further, 54 patients with nAMD were treated with IVAI>10 times (multiple IVAIs). Moreover, the correlation of immediate IOP increase and VR rates with first-time and multiple IVAIs in nAMD was determined. RESULTS: The immediate IOP increase (P=0.16) and VR rates (P=0.50) were almost similar among the four background diseases. The immediate postinjection IOP and age, VR rate and age, immediate postinjection IOP and axial length, or VR rate and axial length were not correlated in the four background diseases. The immediate IOP increase (P=0.66) and VR rates (P=0.28) did not significantly differ between first-time and multiple IVAIs in nAMD. CONCLUSION: Background diseases and number of previous IVAIs have no effect on immediate IOP increase and VR rate. Further, age and axial length have no correlation on immediate IOP increase and VR rate.