Functional and Anatomical Outcomes of Dexamethasone Intra-vitreal Implant in Patients with Resistant Macular Edema Secondary to Retinal Vein Occlusion After Intravitreal Anti-VEGF Injection

Retinal vein occlusion (RVO) is one of the most common causes of vision loss due to retinal vascular disease. Incidence of RVO has been raised in the last years due to increased coexisting systemic vascular risk factors as arterial hypertension, obesity, diabetes mellitus and COVID-19. Macular edema (ME) is a major sight-threatening complication of branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO). BRVO and CRVO have the same pathology, an elevation in the intravascular pressure in the occluded vein leading to vascular wall damage causing leakage of fluid and release of inflammatory cytokines as vascular endothelial growth factor (VEGF), respectively. In the past, the standard treatment for BRVO-related ME was grid laser photocoagulation and for CRVO-related ME was observation. But subsequent randomized controlled trials demonstrated significant functional and anatomical improvements among patients with ME secondary to BRVO or CRVO treated with intravitreal injections of vascular endothelial growth factor (VEGF) inhibitors or corticosteroids compared to those treated with laser only. Anti-VEGF therapy decrease intravenous pressure, enhance blood flow and improve venous diameter and tortuosity. Also, intravitreal corticosteroid injection has been shown to improve vision and central macular thickness (CMT). Dexamethasone intravitreal implant (Ozurdex®, Allergan Inc., Irvine, CA, USA) has potent antiangiogenic and anti-inflammatory effects. Also it decreases the vascular permeability playing an important role in treating ME secondary to RVO. However, majority of eyes have been treated previously then shifted to dexamethasone implant as a second line for treatment of refractory RVO related ME.