Comparison between two intravitreal injection techniques with respect to fluid reflux, intraocular pressure, and therapeutic effect

Abstract

CONTEXT: Effect of fluid reflux on intraocular pressure (IOP) and therapeutic benefits. AIMS: The aim of this study is to compare two intravitreal injection techniques in terms of fluid reflux, short-term IOP changes, and therapeutic effect. SETTINGS AND DESIGN: A prospective, double-blinded, randomized interventional study. SUBJECTS AND METHODS: Sixty eyes were randomly allocated to two groups (direct intravitreal injection technique and oblique intravitreal injection technique). IOP was measured before and immediately after the injection of 0.1 ml comprising of bevacizumab (1.25 mg/0.05 ml) and dexamethasone (0.2 mg/0.05 ml) and then at 30 min after the injection. Occurrence and amount of vitreous reflux were recorded. Best-corrected visual acuity (BCVA) and central macular thickness (CMT) were assessed preinjection and 6 weeks postinjection. RESULTS: IOP (mmHg ± standard deviation) increased significantly immediately after injection to 24.30 ± 3.02 (direct intravitreal injection) and 31.50 ± 3.49 (oblique intravitreal injection). These pressure rise differed significantly between both groups (mean difference: 7.2, P < 0.0001). Thirty minutes after injection, there was no significant difference in IOP increase between the groups. Occurrence and amount of fluid reflux were significantly higher with direct intravitreal injection. There was no significant difference in BCVA and CMT outcome between both groups. CONCLUSIONS: Direct intravitreal injection technique has lower rise in IOP and higher incidence of fluid reflux than the oblique intravitreal technique. Fluid reflux does not cause a therapeutic compromise in terms of BCVA or CMT changes, so the reflux fluid must be the vitreous not the drug. Thus, direct injection technique seems to be the preferred technique.