One of the most common complications of noninfectious posterior uveitis is CME.28
In 2004, Markomichelakis et al. have identified two main patterns of ME, with no statistical significance in relation to the location, or etiology of uveitis: 1) diffuse type (DME), and 2) cystoid type (CME).29
The incidence of CME has been estimated in various studies about 33% of uveitis patients.30 In recent reports, the use of OCT has revealed the CME type in 25–69% of patients with uveitic ME examined.9,29
In essence, the presence of CME was observed especially in higher age of patients at the onset of uveitis, insidious onset of uveitis, persistent duration of an attack of uveitis, a chronic course of uveitis, bilateral involvement. In accord with previous studies,31,32 the occurrence of CME in noninfectious posterior uveitis seems to be associated with systemic disease, or idiopathic uveitis (p = .001), lower BCVA (p = .001), and a refractory course despite the treatment, while no significant association of CME with gender (p = .065) emerged.
It was proven how a single injection of dexamethasone is effective in reducing CMT, which doing a significant gain in visual acuity (AV).33–43
As described by Pleyer et al.,44from our data analysis there was a significant reduction in CMT at M1 (p = 0.001), associated with an improvement in BCVA (p = .002).
No significant difference was observed between the resolution of CME in non-infectious posterior uveitis with known cause (either not associated with systemic disease, and those associated with systemic disease) compared to non-infectious posterior uveitis of idiopathic origin (p = .087).
On the other hand, the CME has reappeared over time in a significant percentage of cases, in 37.5% after 4-month, and 16.1% after 6-month. For instance, Nobre-Cardoso et al.45documented the reappearance of CME in 31.3% of cases treated after 3-month, and Khurana et al.15 described a recurrence of CME after the 6-month in 65% of cases.
If CME persists, getting damaged photoreceptors, with possible serious complications such as macular ischemia, epiretinal membranes (ERM), macular hole.46 In turn, the presence of ERM has a negative correlation with lower visual acuity and CME relapsing.32
Our study is consistent with the OCT data found in the literature for defining the uveitis macular ME features,47 such as the CMT,31 different patterns of edema,29 the associated vitreoretinal interface.48
CMT was very thick (> 300µm) at inclusion and significantly reduced after the 1-month DEX-implant (p = .001). Only the cystoid form of uveitic ME was included in the study, which the most difficult entity to resolve.32 The presence of ERM associated with CME in a certain percentage of patients (35.7%). Of these, uveitis-CME recurrence despite the DEX-implant occurred in 32.1% of cases of ERM associated.
Regarding the persistence, or the recurrence of uveitis-CME, it was hypothesized the microstructural disruption of the inner and outer blood-retinal-barrier as the result of the release of inflammatory cytokines.49–51 It has already been revealed that the possibility of anatomical and functional modifications of the retinal capillary network can be negatively correlated with the CME recurrence, but it has been demonstrated in diabetic patients.26
To our knowledge, no other studies in the literature estimated the microvascular changes of the retinal capillaries in CME posterior noninfectious uveitis after the DEX-implant have been found. Most of the studies, as seen, were based on follow-up through OCT, widely used in clinical practice.
Although OCT has dramatically transformed the understanding and management of uveitis-CME, it does not allow to evaluate the retinal microvascular characteristics, which could be the cause of the recurrence of CME in uveitis patients.52
OCTA previously has proven being an interesting imaging tool in diagnosis, and management of retinal vasculitis,53–55 and choriocapillaritis,56–57as it allowed to visualize in detail the retinal microvascular changes, which can be so easily assessed and quantified, to accurately identify the area of the FAZ,58 or the parafoveal capillary telangiectasia and shunting vessels,59 or the rarefaction of the perifoveal capillary network.60
The current study suggests use of OCTA among the imaging techniques for identifying microvascular changes during the course treatment with DEX-implant in noninfectious posterior uveitis, whereas the other instruments fail to detect the retinal capillary plexuses.
Although the complete intraretinal and subretinal fluid resorption observed though OCT images after DEX-implant, some microvascular anatomical and functional changes were revealed by OCTA findings.
Our investigation showed a reduction in SVP measurements already within 2-month (84%), reaching 96.4% for up 1-year, however displaying an irregular profile in 69.6% of cases, persisting for up 1-year.
The relapsing uveitis-CME eyes with irregular superficial FAZ profile were in 51%, while the SVP measurements reestablished in 100% of cases.
Conversely, the DVP parameters restored occurred in a lower number of eyes within the 2-month (39.3%), remaining abnormal in 46.4% of cases for up 1-year.
Despite DVP restored in 53.6% of cases for up 1 year, a capillary rarefaction ring around the FAZ appeared in 80.4% of cases.
The relapsing uveitis-CME eyes with abnormal DVP parameters were in 41% of cases, of which 92.1% showed a rarefaction ring had abnormal DVP.
Enlarged deep FAZ was found in patients with posterior uveitis, both in the presence and absence of ME.61 Significant changes in DVP parameters were previously detected in uveitis-CME, matching with the site of intraretinal cystoid spaces in the inner retina (inner nuclear and plexiform layers).62 The enlarged deep FAZ coupled with the rarefaction of the perifoveal capillary network was described in other ocular diseases as microstructural damage to the retinal barrier.63,64
Persistent damage of the retinal capillary layers, both of the superficial, and particularly of the deep plexuses, may further explain the reason of the relapsing uveitis-CME.
In using the OCTA of the patient with uveitis, we also encountered some difficulties to be taken into account, such as the possibility of the presence of synechiae, vitreous turbidity, dense cataracts, which may hinder good quality in image acquisition; to these limitations it is necessary to add age heterogeneity and patient collaboration, which were also crucial for a good quality of acquisition.