Red eyes, commonly known as pink eye or conjunctivitis, are a widespread affliction often associated with seasonal allergies, bacterial infections, or common viral illnesses. This eye inflammation occurs when the delicate membrane covering the eye becomes irritated, causing redness of the white part of the eye and the inner eyelid. As the COVID-19 pandemic introduced unexpected symptoms, a question arose regarding the connection between this common eye condition and the novel coronavirus. Understanding this link requires examining the frequency and biological mechanisms by which the SARS-CoV-2 virus can affect the ocular surface.
Red Eyes and COVID-19 Prevalence
Red eyes, or conjunctivitis, have been identified as a possible symptom of COVID-19, though it is generally uncommon compared to respiratory symptoms like cough or fever. Early studies suggested the prevalence of ocular manifestations was low, affecting between 1% and 3% of patients. More comprehensive analyses later indicated that the overall pooled prevalence of eye symptoms, with conjunctivitis being the most common, was approximately 11% among confirmed cases. The frequency of this symptom appeared to shift with the emergence of different viral variants, such as the Omicron subvariant Arcturus (XBB.1.16), which was noted to increase the risk of conjunctivitis, particularly in pediatric patients. While red eyes can occasionally be the initial or sole sign of infection, they are much more frequently accompanied by classic systemic symptoms like fever, fatigue, and respiratory issues.
The Biological Mechanism of Viral Conjunctivitis
The SARS-CoV-2 virus is capable of infecting the ocular surface because conjunctival cells express the necessary receptors for viral entry. The primary entry point is the Angiotensin-Converting Enzyme 2 (ACE2) receptor, which is prominently found on the superficial epithelial cells of the conjunctiva and cornea. The virus’s spike protein binds to the ACE2 receptor, a process facilitated by the enzyme TMPRSS2, allowing it to invade the cell. Viral replication within these cells triggers an inflammatory response in the conjunctiva, manifesting as redness, swelling, and increased tearing. Since the eye is a mucosal surface, it is susceptible to infection through airborne droplets or hand-to-eye contact, and viral genetic material has been detected in the tear film of some infected individuals.
Distinguishing COVID-Related Red Eyes from Other Causes
Distinguishing COVID-related conjunctivitis from other common causes involves analyzing the accompanying symptoms and the nature of the eye discharge. Viral conjunctivitis, including that caused by SARS-CoV-2, typically presents with watery discharge and a gritty sensation, often beginning in one eye and spreading to the other within a few days. Allergic conjunctivitis is characterized by intense itchiness and a clear, watery discharge, frequently affecting both eyes simultaneously, and does not cause systemic symptoms like fever. Bacterial conjunctivitis, by contrast, is usually marked by a thick, sticky, colored discharge that can cause the eyelids to crust over upon waking. The presence of fever, cough, fatigue, or loss of taste or smell alongside red eyes strongly suggests a systemic viral infection like COVID-19.
When to Seek Testing and Medical Advice
If red eyes occur along with typical systemic COVID-19 symptoms such as fever, persistent cough, or significant fatigue, you should seek COVID-19 testing. For simple red eyes without severe accompanying symptoms, self-care measures can help manage the discomfort, such as applying cool compresses and using over-the-counter lubricating artificial tears. Contact lens wearers should switch to glasses until symptoms resolve to prevent potential complications. You should seek immediate medical attention if you experience “red flag” symptoms, including severe eye pain, sudden changes in vision, or extreme sensitivity to light. An eye care professional can properly diagnose the underlying cause of the conjunctivitis and rule out any vision-threatening issues.