COVID-19–associated acute macular neuroretinopathy
C. Optical coherence tomography
Optical coherence tomography (OCT) and IR images can be useful imaging modalities to detect acute macular neuroretinopathy (AMN). Findings include a circular dark lesion on IR images. On transverse OCT images, outer nuclear layer hyperreflectivity combined with interdigitation zone hyporeflectivity (Figure 2) correspond to the dark geographic lesions seen with IR imaging (Figure 1). Lesions correspond subjectively to the central or paracentral, partial-depth scotoma. While the fundus examination results may remain normal for up to 2 months after the onset of symptoms, changes are usually detected early using multimodal imaging. The fluorescein angiography results are in approximately 70% of AMN cases, may demonstrate subtle hypofluorescence in 20% of lesions, or may demonstrate hypofluorescence only in the late phase in the remaining 10% of lesions. Similarly, electroretinogram results are normal in most cases (90%), and 10% will have reduced a-wave amplitudes.1 Multifocal electroretinogram has also been proposed and shows focal wave-form abnormalities.2