Acute macular neuroretinopathy has a poorly understood pathology and pathogenesis. Recent evidence has indicated a lesion in the outer retina which is now confirmed in this report using high resolution optical coherence tomography.

Case report

A 27-year-old woman presented with a 6-day history of acute painless blurring of vision in both eyes commencing 2 days after a flu-like illness. She described discrete paracentral scotomas in both eyes and was able to draw these precisely on an Amsler chart (Figure 1). Visual acuities were 6/9 bilaterally with normal pupils and clear ocular media. There was subtle, patchy red discolouration at the macula bilaterally, and a solitary haemorrhagic cotton wool spot in the right eye. Scanning laser ophthalmoscopic (SLO) infra-red imaging showed dark areas corresponding to the abnormalities on Amsler (Figure 2). High-resolution optical coherence tomography (OCT) showed disruption of the photoreceptor inner /outer segment junction in the same areas, with associated focal thinning of the outer nuclear layer (Figure 3). After 8 months, the patient still complained of paracentral scotomas, which were less dense and slightly more diffuse, corresponding to improved OCT appearance (Figure 3) and less discreet changes on the infra-red images (Figure 4). Visual acuities remained 6/9 bilaterally.

Figure 1
figure 1

Left eye Amsler grid showing scotomas at presentation.

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Figure 2
figure 2

Colour fundus photographs and infra-red images at presentation, 2 weeks after the onset of symptoms. Subtle red perifoveal lesions are easily visualised on infra-red imaging. A haemorrhagic cotton wool spot is seen on the right superotemporal arcade.

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Figure 3
figure 3

High-resolution OCT images (Cirrus HDOCT, Carl Zeiss Meditec, Jena, Germany). (a–c) Right macula. A 6-mm horizontal raster scan, as illustrated by the blue line on the red-free scout image (a), is shown at presentation (b) and after 8 months (c). An area of focal disruption of the photoreceptor inner/outer segment junction is seen (arrows) with thinning of the outer nuclear layer, corresponding to the lesion seen on red-free imaging. The normal reflectivity of the inner/outer segment junction in an unaffected area is indicated by the arrowheads. Partial reconstitution of this layer is seen after 8 months. (d–f) Left macula. The same abnormality is shown (arrows) with arrowheads again showing the normal photoreceptor inner/outer segment junction. After 8 months, only a small area of residual abnormality is seen.

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Figure 4
figure 4

: Infra-red reflectance images 8 months after the onset of the symptoms showing partial resolution of the abnormalities.

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Comment

Acute macular neuroretinopathy (AMNR) is a rare and poorly understood condition. The original description by Bos and Deutman1 has been followed by numerous reports implicating precipitants including, most commonly, an acute viral illness1, 2 but also the administration of vasoconstricting drugs3 and acute systemic hypotensive episodes.4 Although Bos and Deutman1 originally proposed a lesion in the inner retina, subsequent observations have suggested the outer retina to be the location of the pathology.2, 5, 6 One or two retinal flame-shaped haemorrhages are also often seen.2 A recent report showed disturbance of the inner/outer segment junction on ultra-high-resolution OCT in a proposed case of AMNR,7 but the features of the case were not typical (age over 50 years, unilateral non-classical lesion, and no predisposing event). The high-resolution OCT images in our patient clearly show focal abnormality in the photoreceptor layer, corresponding to the lesions on infra-red imaging, with preservation of inner retinal architecture. Whether a direct viral effect or immunologic phenomenon is responsible remains unclear, although abnormalities of choroidal perfusion may be responsible for cases associated with the use of adrenaline or noradrenaline (with or without antecedent acute systemic hypotension). This report is further evidenced that the pathology in this unusual condition is located in the outer retina/photoreceptors and not, as was originally thought, in the inner retina. The condition may perhaps be more accurately described as ‘acute macular outer retinopathy’.