OBJECTIVE To evaluate the effect of the Honan intraocular pressure reducer (HIPR) on vitreous reflux during intravitreal (IVT) injection. METHODS Prospective, comparative, controlled, investigator-blinded, randomized clinical study. Sixty eyes of 60 patients who underwent IVT injection were allocated into 2 groups with or without using the HIPR. Vitreous reflux was estimated by measuring largest diameter of the conjunctival bleb formed after IVT injection. Preoperative intraocular pressure (IOP) before and after application of the HIPR and IOP immediately postoperatively and 3 and 10 minutes postoperatively were evaluated. RESULTS The mean amount of vitreous reflux was significantly less with the HIPR than without the HIPR (1.46±1.04 mm vs 2.61±1.37 mm; p<0.001). The preoperative IOP was significantly lower with the HIPR than without the HIPR (11.62±4.04 mmHg vs 16.26±3.86 mmHg; p=0.026). The 3-minute postoperative IOP was 31.34±3.16 mmHg with the HIPR and 32.61±5.62 mmHg without the HIPR (no statistical significance; p=0.345). CONCLUSIONS The HIPR prevents vitreous reflux after IVT through a reduction in the preoperative IOP. However, the HIPR appears not to affect the postoperative course of transient IOP elevation.