Acute Macular Neuroretinopathy

SALIENT FEATURES

Acute macular neuroretinopathy (AMN) is a rare condition classically defined by a wedge-shaped or petaloid lesion directed toward the fovea (Figure 13.1).¹,²
Patients most commonly complain of a paracentral scotoma with mild vision loss.¹,²
This condition is typically found in Caucasian females in the third decade of life.²
The pathogenesis has not been completely elucidated; however, recent studies suggest a microvascular etiology.³,⁴ An inflammatory cause is less likely.
AMN has been shown to be associated with mainly nonspecific illnesses, use of oral contraceptives and vasoconstrictors, and potentially vasoactive events.²
Color fundus photography may illustrate a reddish wedge-shaped parafoveal lesion but can otherwise be normal, and diagnosis usually relies on spectral-domain optical coherence tomography (OCT) and near-infrared reflectance (NIR).²

OCT IMAGING

OCT imaging is critical to make the diagnosis of AMN. NIR is also valuable and displays a tear drop or wedge-shaped hyporeflective lesion in the parafoveal region (Figure 13.2A).²

Acutely, OCT most commonly displays hyperreflectivity of the outer nuclear layer (ONL) with radial extension into the Henle fiber (HFL) and outer plexiform layers (OPLs), suggesting photoreceptor cell body and axon disruption (Figure 13.2B).²,⁵

FIGURE 13.1 Multicolor (A), near-infrared reflectance (NIR) (B) and en-face optical coherence tomography (OCT) (C) images of the characteristic petaloid pattern of acute macular neuroretinopathy (AMN). Note that the petaloid lesion identified with NIR and en-face OCT colocalizes with ellipsoid zone attenuation with the corresponding cross-sectional OCT B-scan.

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