Pratik Bikkannavar
Speciality Trainee, Royal Free London NHS Foundation Trust
Introduction and Presentation:
Acute macular neuroretinopathy (AMN) is a condition that was first described in a four- patient case-series by Bos and Deutman in 1975 (1). It is commonly classed as one of the white-dot syndromes, a group of inflammatory chorioretinopathies characterised by multiple focal chorioretinal lesions seen on slit-lamp fundoscopy. AMN is an uncommon condition known to generally affect young healthy Caucasian females 20-40 years old and is associated with a spectrum from transient to longer-term visual disturbance. The commonest presentation of AMN is one or more wedge-shaped paracentral scotomas of acute to subacute onset, developing over days to weeks, with patients also known to variably report a decline in visual acuity, metamorphopsia, and floaters. One or both eyes may be affected (2).
Pathophysiology and Aetiology:
The name of AMN was originally conceived by Bos and Deutman on the basis of the early impression that the superficial layers of the inner retina were involved in the disease. Since then, further research including the use of advanced imaging techniques has suggested that the pathology in AMN begins in the outer nuclear and outer plexiform layers, and over time disrupts the junction between the outer nuclear layer and the retinal pigment epithelium (3). The associations of AMN documented over the years include a preceding non-specific coryzal illness, oral-contraceptive use, the use of sympathomimetic drugs, and more recently COVID-19 vaccination and infection (4). Whilst the detail of the pathogenesis is an ongoing topic of research, the current consensus is that retinal microvascular dysfunction and ischaemia likely underlie AMN (5).
Diagnosis:
The diagnosis of AMN is based upon a combination of the clinical history and symptoms, slit- lamp fundoscopic findings, and retinal imaging. Parafoveal petal-shaped retinal lesions reddish-brown in colour are the characteristic lesions reported on slit-lamp fundoscopy and retinal photography, although these may also be round or oval in shape. The lesions may be subtle and thus difficult to visualise in early-stage disease but are known to reliably correspond to any scotomas reported. These lesions become less prominent over time but typically do not disappear altogether. On ocular coherence tomography these lesions manifest as hyperreflective plaques localised to the outer nuclear and outer plexiform layers, with later-stage disease being associated with thinning of the outer nuclear layer and disappearance of the plaques. Generally, no significant changes are found on fluorescein and indocyanine-green angiography (2,5).
Management and Prognosis:
No effective treatment is currently known for AMN. Follow-up may be organised for the patient at a frequency deemed appropriate by the responsible clinician, in order to monitor the progress of the condition, taking into account the severity of the patient’s symptoms and any ocular comorbidities if present. The disease is typically self-limiting with the symptoms improving over time, although some patients may find symptoms persisting in the longer- term to some degree (2,5). Following resolution, the recurrence of AMN is also known to occur (6,7).
References:
- Bos PJM, Deutman AF. Acute Macular Neuroretinopathy. Am J Ophthalmol. 1975 Oct;80(4):573–84.
- Bhavsar K V, Lin S, Rahimy E, Joseph A, Freund KB, Sarraf D, et al. Acute macular neuroretinopathy: A comprehensive review of the literature. Surv Ophthalmol. 2016 Sep 1;61(5):538–65.
- Fawzi AA, Pappuru RR, Sarraf D, Le PP, McCannel CA, Sobrin L, et al. Acute macular neuroretinopathy: Long-term insights revealed by multimodal imaging. Retina. 2012 Sep;32(8):1500–13.
- Jalink MB, Bronkhorst IHG. A Sudden Rise of Patients with Acute Macular Neuroretinopathy during the COVID-19 Pandemic. Case Rep Ophthalmol. 2022 Feb 14;13(1):96–103.
- Sadda SR, Schachat AP, Sarraf D, Freund KB, Hinton DR, Wilkinson CP, et al. Ryan’s Retina: Seventh Edition. Seventh ed. [London]: Elsevier [London]; 2023.
- Hoang A, Khine KT, Houghton OM. Recurrence of Acute Macular Neuroretinopathy. Ophthalmic Surg Lasers Imaging Retina. 2018 Dec 1;49(12):962–8.
- Oliver JC, DePoe SA. Case Report: Recurrent Acute Macular Neuroretinopathy— Monitoring Recovery with Multimodal Imaging. Optometry and Vision Science. 2023 Mar;100(3):232–7.