The additive effect of intravitreal dexamethasone combined with bevacizumab in refractory diabetic macular edema

To evaluate the short-term structural and visual outcomes and side effects associated with intravitreal dexamethasone (IVD) combined with bevacizumab (IVB) in treating patients with diabetic macular edema (DME) and an inadequate response to anti-vascular endothelial growth factor (anti-VEGF) agents.

In this prospective interventional case series, a total of 81 eyes of 81 patients with type 2 diabetes mellitus (T2DM) and refractory DME were included and assigned to one of two groups: I) those receiving three monthly intravitreal injections of combined bevacizumab and dexamethasone (IVB+IVD) and II) those receiving three monthly intravitreal injections of bevacizumab alone (IVB). The primary outcome was the inter-group difference in central macular thickness (CMT); secondary outcomes included best-corrected visual acuity (BCVA), baseline optical coherence tomography (OCT) biomarkers, and intraocular pressure (IOP) one month after the last injection.

Reduction in CMT and improvement in BCVA were significantly greater in the IVB+IVD group than the IVB group (109.88±156.25 vs. 43±113.67, respectively, P=0.03; and -0.13±0.23 vs. -0.01±0.17, respectively, P=0.008). Presence of neurosensory retinal detachment (NSD) (P<0.001) and complete inner segment/outer segment junction (IS-OS) disruption (P=0.049) on baseline OCT scans were associated with further CMT reductions in response to IVD. Conversely, identifiable epiretinal membrane (ERM) (P=0.002) and multiple hyperreflective foci (>20) (P=0.049) were associated with smaller reductions in CMT. Vitreomacular traction correlated with worse visual outcomes in the IVB+IVD group (P=0.003). The intergroup IOP difference was not clinically significant.

In patients with refractory DME, addition of IVD to the standard IVB regimen can improve visual and structural outcomes without increasing the risk of endophthalmitis, IOP rise, or intraocular inflammation. Patients with NSD are more likely to respond well to IVD. The presence of ERM may predict poor treatment response.