COVID-19 is primarily known as a respiratory illness, but the SARS-CoV-2 virus can affect numerous organ systems, including the eyes. Ocular involvement can manifest in a wide spectrum of ways, ranging from mild surface irritation to severe, internal complications that pose a direct threat to vision.
Understanding these effects requires looking at both the direct action of the virus on eye tissues and the body’s generalized inflammatory response. The eyes can be an early indicator of infection and, in some cases, a site of lasting concern.
Immediate Ocular Symptoms
The earliest and most common signs of ocular involvement appear on the surface of the eye during the acute phase of infection. The most frequent manifestation is viral conjunctivitis, or pink eye, which affects a subset of patients. This condition presents as redness of the eye and inner eyelid, often accompanied by watery or mucoid discharge.
Many individuals also experience excessive tearing (epiphora) and a gritty feeling, or the sensation of a foreign body. A heightened sensitivity to light (photophobia) is another noticeable early symptom. Patients may also report a dull ache or soreness, sometimes described as pain upon moving the eyes. These acute surface symptoms are generally mild, transient, and typically resolve on their own within two weeks.
Biological Pathways of Viral Entry
The eye is susceptible to SARS-CoV-2 infection due to specific molecular structures on the ocular surface cells. The virus gains entry by binding its spike protein to the Angiotensin-Converting Enzyme 2 (ACE2) receptor. ACE2 receptors are expressed in the epithelial cells of the conjunctiva and the cornea.
For successful invasion, a second protein, the transmembrane protease serine type 2 (TMPRSS2), is required to prime the spike protein. This protease is co-expressed with ACE2 on ocular surface tissues, creating the complete biological gateway for viral entry.
This biological pathway suggests the eye is not only a possible entry point for the virus but also a potential reservoir for viral shedding. SARS-CoV-2 genetic material has been detected in the tear film of infected patients, sometimes even before respiratory symptoms begin. This finding underscores the importance of the eye as a mucosal surface that can contribute to person-to-person transmission.
Acute Vision-Threatening Complications
COVID-19 can incite systemic changes that lead to serious, vision-threatening complications within the eye’s internal structures. The virus often triggers hypercoagulability, an increased tendency for blood clots to form throughout the body. When these clots travel to the delicate blood vessels of the retina, they can cause severe blockages.
Retinal artery occlusion, often called an eye stroke, occurs when a clot blocks an artery supplying the retina, leading to sudden, painless vision loss. Retinal vein occlusion results from a blockage in a vein, preventing blood from draining and causing retinal swelling and hemorrhaging. These vascular events can permanently damage the light-sensing cells of the retina.
Another form of damage linked to systemic inflammation is the appearance of “cotton wool” spots on the retina. These white, fluffy patches represent localized areas of nerve fiber layer damage and tissue death due to micro-infarctions in the small retinal capillaries. While these spots may not always impact central vision, they are a clear sign of vascular compromise related to the viral infection.
The intense, generalized inflammation can also affect the optic nerve, which transmits visual information to the brain. This can result in optic neuritis, causing pain with eye movement, reduced color vision, and temporary or persistent vision loss. Less commonly, neuro-ophthalmic manifestations such as cranial nerve palsies can occur, leading to double vision (diplopia).
Persistent Visual Changes After Recovery
A distinct set of visual complaints can persist long after the respiratory illness has resolved, often categorized as “Long COVID” symptoms. Chronic dry eye syndrome is frequently reported, manifesting as persistent dryness, burning, or grittiness. This may be due to the virus disturbing the tear film balance or causing low-grade inflammation of the ocular surface.
Many individuals experience prolonged photophobia, where normal indoor lighting causes significant discomfort and eye strain for months. Persistent blurred vision is another common complaint that is not always correctable with prescription lenses. This blurring can relate to visual fatigue or problems with the eye’s ability to focus over time.
Eye pain lasting for weeks or months post-infection is also reported, suggesting a lingering inflammatory or neuropathic process. These chronic visual changes are considered part of the post-viral syndrome impacting the nervous system and immune response. Continued monitoring and specialized visual rehabilitation are necessary for individuals recovering from these systemic effects.