Shingles is caused by the reactivation of the varicella-zoster virus, the same pathogen that causes chickenpox. The virus remains dormant in nerve tissues after the initial infection, and its reawakening leads to the painful, blistering rash known as shingles. Shingles can severely affect the eye, a condition that constitutes a medical emergency. The potential for vision loss makes prompt diagnosis and treatment necessary to prevent long-term damage.
Understanding Herpes Zoster Ophthalmicus (HZO)
The specific form of shingles that impacts the eye area is called Herpes Zoster Ophthalmicus (HZO). This condition arises when the dormant virus reactivates within the trigeminal ganglion, a cluster of nerve cells responsible for sensation in the face. The virus spreads along the ophthalmic division (V1 branch) of the trigeminal nerve. This nerve pathway supplies sensory innervation to the forehead, upper eyelid, and structures within the eye, making the eye vulnerable to infection.
The V1 branch includes the nasociliary nerve, which innervates the tip of the nose and internal eye structures. HZO accounts for approximately 10–20% of all shingles cases. Once the virus travels along this nerve, it can reach the skin of the face and the tissues of the eye, causing inflammation and damage. The resulting disease is unilateral, affecting only one side of the face and one eye.
Identifying the Critical Symptoms
The earliest warning sign is a painful, blistering rash appearing on the forehead, upper eyelid, or scalp on one side of the face. A particularly important indicator is the presence of lesions on the tip, side, or root of the nose, known as Hutchinson’s sign. This sign indicates involvement of the nasociliary nerve, which shares a pathway with internal eye structures, significantly raising the risk of ocular complications.
If the eye is involved, patients experience severe ocular symptoms. These include intense, burning eye pain, noticeable redness, and a feeling of foreign body irritation. Vision can become blurred, and sensitivity to light (photophobia) is a common complaint. Eyelid swelling often occurs, signaling active inflammation in the surrounding tissues.
Managing the Acute Infection
Managing HZO requires rapid intervention, primarily using systemic antiviral medications. Treatment must begin within 72 hours of the onset of the skin rash to effectively limit viral replication and prevent further nerve damage. The most commonly prescribed oral antiviral drugs include acyclovir, valacyclovir, or famciclovir, typically taken for a 7- to 10-day course. Valacyclovir and famciclovir offer a simpler dosing schedule and better bioavailability compared to acyclovir.
Managing the resulting inflammation is also a necessary part of the acute treatment phase. A specialist, often an ophthalmologist, may prescribe topical steroid drops to control inflammation inside the eye, such as in cases of anterior uveitis. For severe cases or immunocompromised individuals, intravenous acyclovir may be required for 7 to 10 days, sometimes followed by a transition to oral medication. Frequent monitoring by an eye care professional is mandatory to track intraocular pressure and assess the extent of corneal involvement.
Long-Term Ocular Complications and Prevention
Even with timely treatment, HZO can lead to severe and potentially permanent ocular complications. One debilitating outcome is postherpetic neuralgia, a chronic nerve pain that can persist for months or years after the rash resolves. Within the eye, inflammation can cause scarring of the cornea, the clear front surface of the eye, leading to permanent vision impairment. The inflammatory process can also affect the eye’s fluid drainage system, causing a rise in intraocular pressure that can result in secondary glaucoma and damage to the optic nerve.
Vision loss can occur from inflammation affecting the retina or the optic nerve. The most effective public health measure to avoid these complications is vaccination. The recombinant zoster vaccine, Shingrix, is highly recommended for adults aged 50 years and older, offering over 90% efficacy in preventing shingles. This vaccine provides a strong defense against viral reactivation, significantly reducing the risk of developing HZO and associated severe eye damage.