Bloodshot eyes, technically known as ocular redness or conjunctival injection, occur when tiny blood vessels on the eye’s surface become swollen and visible. This condition is a reported symptom of COVID-19. Ocular redness often manifests as viral conjunctivitis (pink eye) or results from the body’s widespread inflammatory response to the SARS-CoV-2 virus. While eye redness is a recognized symptom, it appears in a relatively small percentage of COVID-19 cases.
Mechanisms of Viral Eye Irritation
The SARS-CoV-2 virus is capable of directly infecting the eye because the ocular surface contains the necessary cellular machinery for viral entry. The angiotensin-converting enzyme 2 (ACE2) receptor, which the virus uses to gain access to cells, is expressed in the epithelial cells of the conjunctiva and the cornea. The presence of these receptors creates a pathway for the virus to establish a localized infection in the eye tissue.
Once the virus infects these cells, it triggers an inflammatory response in the conjunctiva, the clear membrane covering the white part of the eye and the inner surface of the eyelids. This inflammation causes the small blood vessels in the area to dilate, resulting in the visible redness characteristic of conjunctivitis. This ocular manifestation is believed to be a possible route for the virus to enter the body, and the virus has been detected in the tear fluid of some patients.
Beyond direct infection, eye redness can also be an indirect result of the systemic infection caused by COVID-19. The body’s immune reaction releases signaling proteins known as cytokines, which contribute to widespread inflammation throughout the body. This systemic inflammation can cause the blood vessels in the eyes to widen, even without a direct viral presence in the conjunctiva. This effect is a broader consequence of the body reacting to the virus, rather than a localized ocular infection.
Common Non-COVID Causes of Eye Redness
While COVID-19 can cause ocular redness, most instances of bloodshot eyes are due to other common and unrelated factors. One frequent cause is allergic conjunctivitis, which results from the eyes reacting to environmental triggers like pollen, dust, or pet dander. This allergic reaction typically causes both eyes to become red, watery, and itchy as the body releases histamine.
Dry eye syndrome is another widespread cause where the eyes do not produce enough quality tears to maintain proper lubrication. Factors such as prolonged screen time, environmental conditions, or certain medications can exacerbate dry eye, leading to surface irritation and chronic redness.
Eye redness may also signal a different type of infection, such as bacterial conjunctivitis. Bacterial infections usually involve a thicker, pus-like discharge that can cause the eyelids to stick together. Additionally, a subconjunctival hemorrhage appears as a bright red patch on the white of the eye when a tiny blood vessel breaks. This often results from physical strain, such as coughing or heavy lifting, and is usually harmless, clearing up on its own.
When to Consult a Healthcare Provider
A person should consult a healthcare provider if their eye redness is accompanied by specific warning signs that suggest a more complicated or urgent issue. These red flags warrant a professional evaluation:
- Severe or sudden eye pain.
- Abrupt changes in vision.
- Intense sensitivity to light (photophobia).
- The appearance of a thick, yellow, or greenish discharge.
If eye redness occurs alongside systemic symptoms associated with COVID-19, such as fever, persistent cough, or loss of taste or smell, a medical consultation is appropriate. These combined symptoms suggest the need for immediate COVID-19 testing and adherence to local isolation protocols.
Seek professional guidance if eye symptoms persist or worsen after several days, even if they were initially mild. An optometrist or ophthalmologist can perform a comprehensive examination to check for conditions like uveitis or corneal complications, which require specific intervention. Prompt evaluation ensures that any potential vision-threatening issues are addressed quickly.