Name

Etude en OCTA de l'atteinte des plexus capillaires rétiniens et choroïdiens dans la neuropathie optique ischémique antérieure aiguë non artéritique

To analyze the retinal and choroidal microvasculature in patients with nonarteritic anterior ischemic optic neuropathy (NAION) using optical coherence tomography angiography (OCT-A).

In this case–control retrospective observational study, patients with atrophic NAION (at least 3 months after onset of symptoms) and normal subjects underwent a complete ophthalmic examination including spectral-domain OCT, visual field (VF) and OCT-A. Whole en-face image vessel density (wiVD) was used to assess retinal blood flow of the radial peripapillary capillaries (RPC), circumpapillary RPC vessel density (cpVD), superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaris (CC). Statistical correlations between wiVD measurements and visual acuity, VF parameters, retinal nerve fiber layer (RNFL) and combined retinal ganglion cell and inner plexiform layers thickness were analyzed.

Twenty-four patients (26 eyes) with NAION and 24 age-matched normal controls (NC) (24 eyes) were included. OCT-A showed significant reduction of the RPC wiVD (P<0.0001) and the cpVD (P<0.0001) in NAION eyes compared with NC and correlated with RNFL thickness (P=0.002, P=0.004), visual acuity (P=0.042) and the mean deviation (MD) of the VF (P=0.001). Macular OCT angiograms showed capillary rarefaction in the SCP (P< 0.0001) and DCP (P<0.0001) in the NAION group, both correlated with visual acuity (P=0.02, P=0.024). However, wiVD of the CC was not significantly different between the two groups in the peripapillary (P=0.218) and macular (P=0.786) areas.

This OCT-A study showed three main results concerning NAION: (1) rarefaction of RPC was strongly correlated with BCVA, thickness of the pRNFL and visual field parameters, (2) macular vessel density was lower in SCP and DCP and correlated with BCVA and (3) there was no difference concerning vessel density in the pCC and mCC.

Retinal capillaries depend on the central retinal artery and therefore should not be affected by the abnormal posterior ciliary artery flow in NAION. The mechanism by which they are altered is multifactorial. Papilledema (due to swelling of the ischemic axons) compresses the capillaries located in the most superficial layers of the retina, which aggravates tissue ischemia in a vicious cycle. This rarefaction has never been observed in fluorescein angiography, certainly due to the limitations of this technique in terms of resolution and its ability to differentiate the vascular plexus.

In two recent case reports of AAION in giant cell arteritis, Rougier et al. and Balducci et al. demonstrated that choroidal ischemia seen on fluorescein angiography was also well defined with OCT-A segmented on the choroidal vessel. Larger comparative studies are necessary to determine if OCT-A can be a useful tool to distinguish between NAION and AAION.

OCT-A provided detailed visualization of the peripapillary and macular retinal capillary rarefaction, correlated with VF and visual acuity loss. OCT-A could be a useful tool for quantifying and monitoring ischemia in NAION.