**5. OCTA in challenging macular disorders**

#### **5.1 Vaso-occlusive disorders**

Retinal vein occlusions (RVOs) are one of the visually disabling pathologies that lead to impaired capillary perfusion and retinal ischemia. OCTA has the ability to view the retinal vasculature in details as seen in FFA and SD-OCT, which allows accurate evaluation of the microvascular abnormalities including areas of capillary non-perfusion, shunt vessels, vascular dilatation, enlarged the FAZ size, foveal atrophy, intraretinal oedema, and multiple hyporeflective spaces in the inner retinal layers. Bonini Filho et al. reported that OCTA in retinal artery occlusion (RAOs) can accurately delineate retinal capillary plexuses at different levels with the extent of macular ischemia and monitoring vascular flow changes during the disease course [14, 16] (**Figures 8** and **9**).

#### **Figure 8.**

*A case of branch retinal vein occlusion BRVO, OCT-A showed enlarged FAZ with parafoveal flow voids areas in the superficial and deep capillary plexus, more evident in the deep plexus. The b-scan showed interrupted epiretinal membrane with foveal atrophy and multiple hyporeflective spaces in the inner retinal layers. Also, the inner outer photoreceptors segment shows focal disruption up to the ELM.*

#### **Figure 9.**

*A case of central retinal vein occlusion CRVO with the OCTA showed asymmetry between the affected and healthy retina. Both superficial and deep network showed rarefied appearance with small telangiectatic vessels at the level of the deep capillary plexus. The RPE and the choriocapillaris showed multiple dark areas representing areas void of flow caused by the shadow casted by the subretinal fluid.*
