The virus behind your cold sore can quietly hijack your vision for life

Health · Published 3 October 2026 Swipe more like this →

In short: Most people carry the herpes simplex virus, but few realize it can migrate from facial nerves to the cornea. This infection, known as herpes simplex keratitis, causes pain, light sensitivity, and blurred vision. While often treatable, recurrent episodes risk permanent scarring and vision loss if left unmanaged by specialists.

Herpes simplex keratitis is primarily caused by HSV-1, the same virus responsible for common cold sores. After an initial infection, the virus does not leave the body; instead, it remains latent within the facial nerve ganglia. Reactivation can be triggered by factors such as stress, illness, injury, or exposure to bright light, at which point the virus travels down the nerve axon to the surface of the eye.

While primary infections often manifest as mild eyelid swelling or conjunctivitis, recurrent episodes are more dangerous. The virus can cause dendritic ulcers—branching, tree-like lesions on the cornea—that lead to pain and blurred vision. In some cases, the body’s own immune response to the viral presence causes severe inflammation in the corneal stroma, which can result in permanent opacification and blindness. This condition is the leading cause of corneal-derived blindness in developed nations, with roughly 1.5 million new cases globally each year.

Diagnosis is typically clinical, as ophthalmologists recognize the characteristic patterns of the infection. Treatment usually involves antiviral eye drops, gels, or oral medications like aciclovir to suppress viral replication. For severe or recurrent cases, doctors may prescribe steroid drops to manage inflammation, though these must be used carefully to avoid worsening the ulceration. Because roughly half of those affected will experience a recurrence within five years, patients with frequent episodes may require daily suppressive antiviral therapy to protect their long-term ocular health.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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