COVID-19 is a highly contagious disease whose progression can lead to acute respiratory complication or even death. It has also been correlated with conjunctivitis, which results in the “red eye” symptom in patients. Given that the eye allows for direct inspection of the inflammatory changes in conjunctival structures without biopsy, cytokine levels in tear may serve as biomarkers of innate immune system response against COVID-19 infection. In a study which included patients with symptomatic COVID-19, in whom ocular viral infection was confirmed through positive swabs on RT-PCR testing, the tear film concentrations of FN-γ, TNF-α, IL-5, IL-8 and GM-CSF were significantly greater among patients with positive conjunctival swab results as compared to the group negative for SARS-CoV-2 in the conjunctival sac. Additionally, the tear film level of IL-1β appeared to be positively associated with the disease stage (p = 0.035). This may indicate that patients with greater COVID-19 severity had higher levels of such pro-inflammatory cytokines. Accordingly, the IL-1β tear film concentration was found to be higher in patients with pneumonia complicating COVID-19 compared to patients without pneumonia (0.52 versus 0.28 pg/mL; p = 0.0041). As a result, the activation of ocular immune responses observed in the group of symptomatic COVID-19 patients with positive conjunctival swab results may indicate the presence of active infection with SARS-CoV-2 and further studies are needed to clarify the existing ambiguities by detecting the existence of SARS-CoV-2 in different ocular tissues.

References

1. Hennrikus et al. Medicine (Baltimore) 2021; 100: e26936.