Acute Macular Neuroretinopathy: Long-term Insights Revealed by Multimodal Imaging

Purpose: To report the structural and functional changes in acute macular neuroretinopathy (AMN) and their long-term evolution. Multimodal retinal imaging was acquired, including Fourier domain optical coherence tomography (OCT), infrared (IR) reflectance, and near IR autofluorescence (NIA).

Methods: In this retrospective observational case series, detailed clinical history and multimodal imaging are reported in eight patients with AMN. Manual segmentation of the Fourier domain OCT volume scans was done in one patient with the largest AMN lesion to yield retinal sublayer topographic maps.

Results: Two patients were seen within the first 1 to 2 days of symptoms, and both showed outer nuclear and outer plexiform layer hyperreflectivity. Both patients developed enlargement of the lesion over the first week on IR reflectance imaging with a corresponding lateral extension of the outer retinal disruption on Fourier domain OCT. Thinning of the outer nuclear layer persisted in all patients with lesions >100 μm width, and in one patient this thinning worsened over the course of follow-up, as noted on the sublayer maps. This structural abnormality correlated with long-term functional deficits, persisting up to 14 months after the initial episode. Infrared reflectance highlights the lesion best, and abnormalities on near IR autofluorescence may be present.

Conclusion: Acute macular neuroretinopathy acutely affects the outer nuclear and plexiform layers manifesting as OCT hyperreflectivity. The hallmark long-term changes are outer nuclear thinning on Fourier domain OCT and a fading dark lesion on IR reflectance imaging. These changes correspond to focal disruption of the outer segment/retinal pigment epithelium junction on OCT, and not the inner segment/outer segment junction, as previously reported. Optical coherence tomography and near IR autofluorescence abnormalities suggest previously unrecognized melanin and retinal pigment epithelium derangements in this condition.