Peripapillary retinal nerve fibre layer oedema in acute methanol-induced optic neuropathy

Abstract

Background: Methanol poisoning, often from adulterated alcohol, is life-threatening and can cause acute profound visual loss because of methanol-induced optic neuropathy (Me-ION). Identification of distinctive clinical and ocular coherence tomography (OCT) features of Me-ION may help to establish the diagnosis, particularly when patients are unaware that they have ingested methanol.
Methods: This retrospective case series included four patients with acute Me-ION who presented in 2020 during the coronavirus disease 2019 (COVID-19) related alcohol ban in South Africa. Ophthalmic evaluation included assessment of visual acuity and pupillary light reflexes, slit-lamp examination with dilated fundoscopy and retinal nerve fibre layer (RNFL) thickness measurement by OCT.
Results: All patients were examined in the acute phase of Me-ION, with a mean interval of 5.5 days between methanol exposure and ocular examination. Fundoscopy showed peripapillary RNFL whitening and oedema, extending superiorly and inferiorly from the optic disc, but sparing the nasal and temporal areas. In three cases, this correlated with a distinctive pattern of superior and inferior quadrant RNFL thickening on OCT with relative sparing of nasal and temporal quadrants.
Conclusion: This study is the first to associate this specific fundoscopic pattern with distinctive superior and inferior quadrant RNFL oedema on OCT in acute Me-ION.
Contribution: Recognition of this pattern can aid in early diagnosis and timely initiation of life-saving treatment, particularly in cases where patients may be unaware of their methanol exposure.