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Bilateral sequential non-arteritic optic neuropathy post-COVID-19

Corona virus disease 2019 (COVID-19) has been documented to have a spectrum of neuro-ophthalmic manifestations. However, bilateral non-arteritic anterior ischemic optic neuropathy (NAION) post-COVID-19 has not been reported in the literature. We studied the case of a 45-year-old male who presented to our outpatient department (OPD) with bilateral blurring of vision following an episode of COVID-19, 1 month back. Examination and investigations were conclusive of a bilateral NAION. The patient was given a trial of oral steroids. However, the vision loss could not be recovered. Thus, through this case report, we would like to highlight the importance of a close follow-up of patients following COVID-19 infection to detect any sequelae.


Case Report
A 45-year-old male presented with acute-onset blurring of vision in both the eyes. He noticed it in his right eye first; 2 weeks later, he developed similar complaints in the left eye. The diminution of vision was non-progressive and majorly involved the inferior visual field. He was diabetic and hypertensive, well controlled on treatment since past 4 years. Patient gave history of COVID-19 infection 1 month prior to the onset of visual symptoms. He had received oral treatment with hydroxychloroquine(400 mg twice daily for 1 day, then 400mg once daily for 4 days), azithromycin (500 mg once daily)for three days and, paracetamol (650 mg three times a day), Zinc 50 mg OD.
Patient received oral methylprednisolone (1 mg/kg) over 6 weeks (tapering doses every 1 week) after clearance from physician. On follow-up after a month, the visual field defects persisted and disk pallor had set in with gradual resolution of edema in both the eyes.

Discussion
The pathogenesis of COVID-19 remains poorly understood, although there is increasing evidence that inflammatory cytokine storm and viral evasion of cellular immune responses play a fundamental role in disease severity and progression. [6] COVID-19 may predispose patients to thromboembolic events, both in the arterial and venous circulations, due to excessive inflammation, endothelial dysfunction, platelet activation, and stasis. [7] The hypercoagulability induced by COVID-19 could contribute (in addition to other causes) to the development of pulmonary embolism, cerebrovascular accidents (CVAs), deep vein thrombosis, and myocardial infarction. [8][9][10] In the eye, this state of hypercoagulability can lead to formation of thrombi leading to ischemia and compromised vascular circulation, resulting in central retinal vein occlusion or ischemic optic neuropathies. [11] Ischemic optic neuropathy and other sight-threatening ophthalmic disorders (ocular surface disease, acute angle closure, orbital compartment syndrome and vascular occlusions) have also been documented to have been potentiated by proning, as prolonged proning causes periorbital edema with elevation of orbital venous pressures, exacerbated with high-volume fluid resuscitation. [12,13] However, in our case, proning was not done as the patient had mild symptoms; so, it cannot be considered a causative factor.
Neuroretinitis, optic neuritis, and panuveitis as posterior segment involvements due to viral infections are well known. The proposed mechanisms for such ocular manifestations in viral entities include direct viral involvement or a delayed immune response (type 3 hypersensitivity) to the viral antigen. [4] It is usually seen 1-4 weeks following the onset of fever in viral infections. [4] A post-infectious hyperinflammatory disease has been described as an additional outcome after SARS-CoV-2 (Severe Acute Respiratory Distress Syndrome Coronavirus 2) infection following the involvement of a dysregulated adaptive immune system. [14,15] There is scientific evidence that in COVID-19 vasculitis a life-threatening escalation from type 2 T-helper immune response (humoral immunity) to type 3 hypersensitivity (immune complex disease) takes place leading to deposition of immune complexes inside the vascular walls, inducing a severe inflammatory state and a cytokine release syndrome causing ischemic complications. [16] In our case, a middle-aged man presented with disk edema and altitudinal visual field defect after a time lag of a month between acute infection and retinal manifestation, which suggests an immune-mediated pathogenesis post-viral infection which led to bilateral NAION. To the best of our knowledge, this is the first reported case of bilateral NAION following COVID-19 infection. Thus, a close follow-up is needed for patients appearing to have recovered fully from COVID-19, especially those with preexisting comorbidities.

Conclusion
Thus, we report a case of bilateral NAION post-COVID-19 in a middle-aged male secondary to immune-mediated mechanisms compromising the perfusion of the optic nerve. It is imperative to note that the patients recovered from COVID-19 should be followed up closely for COVID-19-related sequelae.

Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.