Coronavirus Disease 2019, Eye Pain, Headache, and Beyond.

BACKGROUND: Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), which causes Coronavirus Disease 2019 (COVID-19), emerged in December 2019 and became a devastating pandemic. Although its respiratory effects can be deadly and debilitating, it can lead to other systemic disorders, such as those causing eye pain and headache. This literature review aims to describe presentations of eye pain and headache in relation to COVID-19, with an emphasis on how these disorders help us to understand the pathophysiology of COVID-19. EVIDENCE ACQUISITION: Literature was mined from the PubMed database using the key terms: "eye pain," "conjunctivitis," "episcleritis," "optic neuritis," "migraine," and "headache" in conjunction with "COVID-19" and "SARS-CoV-2." With the exception of general background pathology, articles that predated 2006 were excluded. Case reports, literature reviews, and meta-analyses were all included. Where SARS-CoV-2 research was deficient, pathology of other known viruses was considered. Reports of ocular manifestations of vision loss in the absence of eye pain were excluded. The primary search was conducted in June 2021. RESULTS: The literature search led to a focused review of COVID-19 associated with conjunctivitis, episcleritis, scleritis, optic neuritis, and myelin oligodendrocyte glycoprotein-associated optic neuritis. Four distinct COVID-19-related headache phenotypes were identified and discussed. CONCLUSIONS: Eye pain in the setting of COVID-19 presents as conjunctivitis, episcleritis, scleritis, or optic neuritis. These presentations add to a more complete picture of SARS-CoV-2 viral transmission and mechanism of host infection. Furthermore, eye pain during COVID-19 may provide evidence of hypersensitivity-type reactions, neurovirulence, and incitement of either novel or subclinical autoimmune processes. In addition, investigation of headaches associated with COVID-19 demonstrated 4 distinct phenotypes that follow third edition of the International Classification of Headache Disorders categories: headaches associated with personal protective equipment, migraine, tension-type headaches, and COVID-19-specific headache. Early identification of headache class could assist in predicting the clinical course of disease. Finally, investigation into the COVID-19-associated headache phenotype of those with a history of migraine may have broader implications, adding to a more general understanding of migraine pathology.