A Chinese study found an increase in cases of acute macular neuroretinopathy (AMN) was associated with Covid-19.  

Immediately following the cessation of China’s zero-Covid public health policy (including contact tracing, mass testing, border quarantine and lockdowns) at the end of 2022, “a significant outbreak of Covid-19 occurred in mainland China, coinciding with an unforeseen surge in clinically diagnosed cases of AMN”, wrote researchers from Beijing Tongren Hospital and Qilu Hospital of Shandong University.  

AMN is rare and characterised by dark reddish, wedge-shaped macular lesions, visible using near-infrared retinal imaging, they said. “Optical coherence tomography (OCT) illustrates structural alterations in the outer retinal layers in AMN. Additionally, retinal deep capillary plexus impairment, as shown by OCT angiography, suggests ischaemia in this disease, although the exact aetiology remains to be determined,” they wrote. 

Of the 33 individuals (62 eyes) recruited, all patients were aware of their visual changes in SAR-CoV-2 Omicron’s very acute phase of illness (within five days, median two days), said researchers. “A high frequency of bilateral ocular changes and a less pronounced female predominance were observed among our patients. The retinal alterations in those patients included typical outer retinal changes consistent with AMN, as well as choriocapillaris perfusion deficits and extensively distributed inner retinal changes.” Smaller retinal inner nuclear layer hyperreflective speckles (41.94 %) were identified as a distinguishing feature from typical paracentral acute middle maculopathy, they added. 

The widespread inner retinal perfusion deficits they observed may serve as potential biomarkers for systemic microcirculation dysregulation in Covid-19, they concluded.