Author: Moncef Khairallah, MD ;   Nesrine Abroug, MD

Department of Ophthalmology, Fattouma Bourguiba University Hospital

Faculty of Medicine, University of Monastir, Monastir, TUNISIA

Retinal vasculitis is a potentially blinding inflammatory condition involving retinal vessels. Fluorescein angiography (FA) is an essential imaging modality for the evaluation and monitoring of uveitis and retinal vasculitis by showing focal or diffuse fluorescein dye leakage from compromised retinal vessels. It is also useful in detecting secondary retinal complications including peripheral retinal ischemia, neovascularization, cystoid macular edema, and macular ischemia. However, FA is invasive, relatively expensive, time-consuming and has a substantially limited depth-resolution due to light scattering phenomenon.

Optical coherence tomography angiography (OCTA) is a new non invasive imaging  tool that allows a detailed, 3D mapping of retinal and choroidal microvasculature. It becomes an essential component of the multimodal imaging approach for the diagnosis and management in patients with chorioretinal disease, including uveitis and retinal vasculitis. In eyes with retinal vasculitis, the evaluation of superficial and deep retinal vascular networks separately thanks to SS  OCTA allows detecting differential involvement of the two layers by an array of qualitative and quantitative microvascular changes. These include areas of retinal capillary hypoperfusion, perifoveal capillary changes including dilated, rarefied and shunting vessels, perifoveal capillary arcade disruption, enlargement of foveal avascular zone, disorganization of capillary network, and decreased capillary vessel density. The deep capillary plexus is usually more severely involved than the superficial plexus.  Areas of capillary hypoperfusion detected by SS OCTA can be correlated with a wide variety of structural changes on SS OCT including segmental thinning of the inner and/or outer retinal layers, reflectivity change, loss of visualization of normal retinal laminations, a fovea-like aspect attributed to a focal loss of tissue filled by the outer nuclear layer, and localized interruption of the ellipsoid zone with focal thinning. In addition, eyes with cystoid macular edema on SS OCT typically exhibit on SS OCTA well-defined black roundish areas completely devoid of flow mainly involving the deep capillary plexus. Resolution of macular edema on SS OCT may or may not be associated with a partial or complete recovery of the normal pattern of retinal capillary plexuses on SS OCTA.