Commentary: Optical coherence angiography in intermediate uveitis: What is the scope?

Abstract

Intermediate uveitis is a subset of uveitis where the vitreous is the primary site of inflammation. It is associated with an infection or systemic disease.[1] The disease affects individuals in all age groups but predominantly affects the third to the fourth decade.[2] In India, the incidence of intermediate uveitis is 1.4/100,000 and its prevalence is 0.25%.[3] Ocular inflammation can cause vascular occlusion, ischemia, capillary leak, and alteration of cellular mediators. Due to the sequalae of uveitis, sight-threatening ocular complications such as macula edema are seen. Early identification, treatment, and monitoring play a crucial role in visual recovery. Regardless of the anatomical location of uveitis, the most common complication of uveitis is macula edema. This is due to the release of inflammatory cytokines that disrupt the inner and outer blood-retina barrier. These changes occur even in anterior uveitis, presumably due to diffusion of inflammatory mediators in the vitreous. Imaging in uveitis is a game changer in the practice patterns of uveitis. Pro-imaging strategies have helped the clinician improvise the quality of eye care and play an important tool in management of ocular inflammation. With the advent of optical coherence tomography angiography (OCTA), an insight into the retinal microvascular changes provides additional information in the pathophysiological changes in uveitis.[4] Based on the definition of intermediate uveitis, the primary site of inflammation is in the vitreous and peripheral retina.[1] Acquiring images of the pars plana, ciliary body, and the peripheral retina is beyond the reach of OCTA. Though there are numerous studies on the microvasculature changes on OCTA in various retinal diseases, little is known about the changes in intermediate uveitis. However, a recent study analyzed the quantitative analyses of macular vascular structures in intermediate uveitis. They demonstrated significantly reduced vascular density in both superficial and deep retinal layers in intermediate uveitis patients [Table 1].[5]Table 1: Studies on OCTA in intermediate uveitisIn a case–control study on intermediate uveitis, reduced vascular density and complexity in superficial as well as deep retinal layers and altered choriocapillaris perfusion were detected. These alterations in OCTA indicates an impairment of the macular microvasculature even in the absence of macular edema.[6] Tian et al.[7] also reported that intermediate uveitis and vasculitis presented with reduced central vessel density. On OCTA, capillary non-perfusion and reduced perfusion was observed more in the choroid, choriocapillaris, and deep capillary plexus than in the superficial capillary plexus. Intermediate uveitis with vasculitis presented more with non-perfusion and hypoperfusion in the deep capillary plexus and superficial capillary plexus than intermediate uveitis without vasculitis. Ischemia on fluorescein angiogram was associated with non-perfusion on wide-field OCTA in superficial and deep capillary plexus. Tian et al.[8] reported another prospective: a cross-sectional study to evaluate vascular changes in patients with intermediate uveitis with or without vasculitis (wide-field montage and central 3 × 3 mm slabs). Though the wide-field images gave important information about peripheral vascular changes, their lower resolution limited the detectability of flow alterations compared to the high resolution of the central scans. Microvascular changes in eyes with intermediate uveitis were found at the level of the superficial capillary plexus, deep capillary plexus, the choriocapillaris, and the choroid. Also, a change of central vascular density found in the central scans did not correlate to alterations found on wide-field OCTA. They also concluded that rather than the presence of an epiretinal membrane and a macula edema, intermediate uveitis had an alteration on the foveal avascular zone size. Capillary changes may be also found beyond the posterior pole on wide-field OCTA. The differences in capillary density and morphology that was detected in uveitis patients shows that the effects of intraocular inflammation can be quantitatively measured even within a 3 × 3 mm2 parafoveal window.[8] Along with investigating the gross changes in the peripheral retina with wide-field imaging studies, OCTA assessment of changes in the parafoveal capillary density and branching complexity provides a unique assessment of disease severity that is not otherwise available. Surprisingly, not only the retinal vasculature is altered but also the choriocapillaris and the choroid is affected in intermediate uveitis. This definitely indicates that long-term studies on this domain are needed. Data on active eyes with intermediate uveitis are sparse. Hence, we would need to evaluate the disease activity which can be visualized using OCTA.