Noninvasive method to reduce vitreous reflux following intravitreal injection

Aim To investigate the role of pre-injection antiglaucoma medications as a noninvasive method to prevent reflux following intravitreal injection (IVI). Patients and methods This single-center prospective randomized study included patients who were planned to receive an IVI of anti-vascular endothelial growth factor ranibizumab 0.05 ml for macular edema for diabetic macular edema, branch retinal vein occlusion, or choroidal neovascular membrane. Patients were randomized into five groups: no intervention (group 1), pre-injection topical brimonidine (group 2), pre-injection oral acetazolamide (Diamox) (group 3), pre-injection topical brimonidine and oral Diamox (group 4), and pre-injection paracentesis (group 5). The primary outcomes were the occurrence and degree of reflux following IVI. In addition, the evaluation of conjunctival bleb estimated the degree of reflux. Patient self-rated pain and early complications were secondary outcome measures. Results A total of 150 eyes of 150 patients were included. Vitreous reflux occurred in 13 (43%), 14 (46.7%), 19 (63.3%), six (20.0%), and four (13.3%) eyes in groups 1–5, respectively (P<0.001). Additionally, higher degrees of reflux were observed in group 1 compared with other groups. Discussion In our study, we raised the question of whether the intraocular pressure (IOP) before injection affects vitreous reflux. Therefore, we compared the effect of different antiglaucomatous medications on lowering the pre-injection IOP, and so decrease the vitreous reflux. We found that in both the paracentesis group and group of combined topical brimonidine and oral Diamox group, vitreous reflux rate is reduced significantly (P<0.001) because in these two groups, the IOP just before the injection was the lowest. Unfortunately, we could not measure the IOP after paracentesis and before the injection to avoid any risk of endophthalmitis, but we consider the paracentesis as a gold standard group for lowering IOP, although it is an invasive procedure. Interestingly, the self-rated pain rate was the same in all groups. Conclusion Pre-injection topical brimonidine combined with oral Diamox may be an effective and noninvasive method to prevent/reduce vitreous reflux following IVI.