Herpes zoster ophthalmicus
Overview
Varicella-zoster virus (VZV) causes 2 distinct syndromes. The primary infection (chickenpox) is a contagious and usually benign febrile illness. Following this infection, virus particles remain in the dorsal root or other sensory ganglion where they may lay dormant for years to decades. As a result of aging, immunosuppressive illness, new stress, or medical treatments, the virus-specific cell-mediated immune responses may decline. Such conditions allow a reactivation of latent VZV and result in a localized cutaneous rash erupting in a single dermatome called herpes zoster (HZ), or shingles. Patients with HZ involving the first division of the trigeminal nerve have a disease process termed herpes zoster ophthalmicus (HZO). HZO was described long ago by Hippocrates, but its relation to VZV was not elucidated until the advent of modern medical tools such as the immunohistochemical assays.
Symptoms
* Ocular manifestations of HZ can vary in time of onset, and patients may have only ophthalmic symptoms without the typical skin rash. One prognostic indicator is the Hutchinson sign, the appearance of typical HZ lesions at the tip, side, or root of the nose. This is the area of skin innervated by the anterior ethmoidal branch of the nasociliary nerve. Because the nasociliary nerve also innervates the cornea such skin lesions may herald ocular involvement. The prognostic value of the Hutchinson sign has been validated in one study.5 * Visual acuity can be considered to be a vital sign of the ophthalmologic examination, and the eye examination should begin here. o Systematically examine the most superficial/external structures first and look for eyelid, conjunctival, and scleral swelling. o Check for extraocular motor integrity and visual field deficits. o Perform a funduscopic examination (dilated if possible), and try to elicit photophobia to ascertain the possible presence of iritis. Decreased corneal sensitivity can be seen when testing with a cotton fiber. o Corneal epithelial lesions may be visible after fluorescein application. o A slit lamp examination should be used to look for cells/flares in the anterior chamber and the presence of stromal infiltrates. o After topical anesthesia of the eye, measure the intraocular pressures (normal pressure is below 12-15 cm H2 O).
Causes
When liberated from the trigeminal ganglion, the reactivated VZV (human herpesvirus type 3) travels down the first division (ophthalmic) of the trigeminal nerve to the nasociliary nerve. This branch then divides to innervate the surface of the globe and the skin on the nose down to its tip. This process typically takes 3-4 days for the virus particles to reach the nerve endings. As the virus travels, it leads to perineural and intraneural inflammation, which may damage the eye itself and/or other surrounding structures.