Herpes Zoster(Ophthal-micus)

TerminologyThere is one virus, VZV, and 2 diseases: 1) Primary Varicella Zoster or chicken pox 2) Herpes Zoster or shinglesFrom the Immune System’s perspective:

The innate immunity is something you are born with and is somewhat structural including the skin and general defenses. The acquired immunity develops as the body comes in contact with infectious agents and includes the humoral immunity (which includes antibodies) and the cell mediated immunity (which includes T cells). Cytotoxic T cells can directly kill virally infected cells when both T cell and infected cell are displaying on their surfaces the correct/complementary proteins. In a cell with a latent virus, no such proteins are displayed, so the virus escapes detection and survives. After primary infection a subset of T cells, memory T cells, hold the key to a programmed and robust immune response if and when reactivation of the virus occurs. Vaccines can use a weakened virus to establish a memory T cell line protective from the full strength wild type virus while bypassing the disease effects of the primary infection (or a reactivation). Currently the CDC recommends the chickenpox vaccine to all infants without contraindications. The shingles vaccine, which has more virus in it than the chicken pox vaccine, is likewise recommended to all adults over 60 years old without contraindications. Contraindications include gelatin and neomycin allergy and especially immunodeficiency. (Yes, some who need the protection of the vaccine most are unable get it, because the vaccine requires some level of host immune response.) Though the details are not understood, with varicella zoster infections, reactivation occurs once, if ever, in patients with normal functioning T cells.

The principle of one reactivation only is the basis for the recommendation to treat with antivirals for the acute reactivation of the virus only. After reactivation the virus is returned to latency indefinitely in the immunocompetent patient, and therefore treatment of recurrent herpes zoster ophthalmicus is approached like an autoimmune condition. No large scale studies have been performed to further clarify treatment of recurrent herpes zoster ophthalmicus.

From the Varicella Zoster Virus’ DNA perspective:

The VZV virus has DNA that it must replicate within a particular human cell in order to survive. Acyclovir is selective to virally infected human cells. Acyclovir feeds faulty DNA parts to the virus, thereby stopping VZV replication. In a randomized control trial of 71 patients with acute herpes zoster ophthalmicus, patients on acyclovir had shorter time to 50% scabbing of skin lesions and lower incidence of the following outcomes than patients on placebo: stromal keratitis, uveitis, and keratic precipitates. In a different randomized control trial of 1,141 pts with acute herpes zoster, patients on valacyclovir reached the following outcome more quickly than patients on acyclovir: time to cessation of pain. Also in the same study, plasma concentrations of acyclovir from valacyclovir were found to be about four times higher than plasma concentrations of acyclovir (from acyclovir). First line antiviral therapy for acute herpes zoster ophthalmicus is 1000g of oral valacyclovir three times a day for seven days (or 500mg of similarly acting oral famciclovir three times a day for seven days).

From the perspective of the disease:

VZV’s selectivity shapes the characteristic features of herpes zoster. VZV is selective to sensory neurons, and so it can cause (focal) pain as well as other sensations spontaneously. (The pain can be accompanied by other constitutional symptoms as well). VZV is latent in a single ganglia with a limited distribution, and so it can, but does not have to, cause a dermatome bound blistering scarring rash.

VZV is also selective to autonomic ganglia, like the ciliary ganglion, so it can cause a tonic pupil. VZV is selective for T cells, and after entry into the bloodstream can affect distant sites and in a few cause life-threatening complications. VZV’s selectivity is based on the envelope proteins on the outside of the virus merging with proteins on the surface of axon terminals or the membranes of other specific cell types. VZV’s DNA is then carried to the nucleus. VZV can then be either actively replicated (causing epidemic disease) or made latent (a prelude to nonepidemic disease). Sensory neurons have their nuclei in the dorsal root and cerebral ganglia, and so chicken pox and herpes zoster predominantly occur in the trunk and head. All sensory ganglia potentially harbor VZV after primary infection, but reactivation usually occurs in just one ganglia or a few adjacent ganglia. The trigeminal ganglia is a cerebral ganglion and its first branch, whose distribution includes the forehead and nose skin to the midline, upper eyelid and globe, is of the three branches, the branch most often affected by herpes zoster. When the tip, side, or root of the nose is involved (Hutchison’s Sign) there is potential ocular disease. Ocular involvement is not correlated with age, sex, or severity of the skin rash. Involvement of any part of the first branch of the trigeminal is called herpes zoster ophthalmicus.

In, Oral Acyclovir in the Treatment of Acute Herpes Zoster Ophthalmicus Cobo et al 1986, a randomized control trial of 71 patients with acute herpes zoster ophthalmicus, the following was noted:

Acyclovir dose of 600mg five times a day for ten days was used. After ten days ocular complications were treated without specific protocols. Prelesion pain preceded the onset of diagnostic skin lesions of HZO in 62% of the entire study group. In none of the 71 patients did the lid margin irregularity or presence of trichiasis or distichiasis necessitate corrective surgery. Conjunctival inflammation was a common nonspecific sign which was present principally at the time of entry and appeared to correlate with lid margin vesicular involvement. Neurotrophic keratopathy as evidenced by corneal erosion or sterile stromal ulceration, occurred in 5 patients, one acyclovir-treated and four placebo-treated. Neurotrophic keratopathy was variable in its time of first appearance (5 to 154 days after entry into the trial) and had a duration of 10 to 278 days. In all cases it was associated with a profound decrease in measured corneal sensation.

Pavan-Langston 2008: Studies by Hung et al and Collum et al on the concentrations of acyclovir in the tear film and aqueous humor in patients on 400 mg (peroral 5 times daily) showed levels of 0.64 umol/l (range, 0.16 –1.45) and 3.26 umol/l (range, 1.10 –5.39), respectively, 4 hours after the last oral dose. The mean effective dose of herpes simplex virus 1 (HSV-1) reducing viral plaque count in tissue culture by 50% ranges from 0.1 to 1.6 umol/l, indicating that the tear film and aqueous levels achieved were well in excess of those needed to eliminate the virus. In comparison to those for HSV, the inhibitory doses for VZV are much higher, at 3 to 4 umol/l, resulting in the need for 4-fold higher drug dosing, as noted above, and less leeway in terms of resistance. To inhibit most strains of VZV, oral dosing of 800 mg 5 times a day is needed to yield peak and trough serum levels of 6.9 umol/l and 0.96 umol/lEqually important, there is also a significant reduction in the incidence and severity of acute dendritiform keratopathy ; incidence, but not severity, of corneal stromal immune

keratitis; and incidence of late-onset ocular inflammatory disease (e.g., episcleritis, scleritis, iritis). Dosing and time to treatment are key factors in treatment success. When adequate treatment of acyclovir was given (800 mg 5 times a day for at least 7 days starting within 3 days after rash eruption), complications occurred in only 4% (2/48) of patients; patients withno treatment or with inadequate treatment had a greater frequency of severe ocular complications: 21% (34/164) and 25% (5/20), respectively.

Anterior segment ocular inflammatory sequelae of HZO were the most common and protracted ocular complications encountered. It is in this group that a beneficial prophylactic effect of acyclovir was most dramatically demonstrated.

After randomization episcleritis was at entry in a higher proportion of the placebo-treated group (thereby confounding further analysis). Episcleritis lasted less than a month in 70% of cases and persisted beyond three months in 15%. Other sclera inflammatory disorders were infrequent. Dendriform keratopathy was likewise present in a high proportion of patients at entry (24%). Here a significant beneficial prophylactic effect with respect to incidence was obtained from acyclovir but the mean duration of the lesion was comparable: 4.9 days in acyclovir-treated patients versus 5.5 days in placebo-treated patients. Stromal keratitis, occurring in 41% of all study patients, was significantly reduced in the acyclovir treatment group. The severity of stromal keratitis and corneal scarring or vascularization consequent to stromal keratitis was not affected by antiviral therapy.

Duration of stromal keratitis, likewise was not affected by acyclovir treatment. While the majority of patients with stromal keratitis responded in 30 days, eight patients (2 acyclovir, 6 placebo) experienced this complication beyond 3 months.

Anterior uveitis: the incidence for the entire study group was 44%. Acyclovir not only provides a beneficial prophylactic effect with respect to anterior uveitis, but the maximum severity scores of this event indicate more severe disease in placebo-treated patients. As with stromal keratitis, duration of this complication of HZO is not significantly ameliorated by acyclovir. Keratic precipitates, a clinical indicator of anterior uveitis, are significantly reduced in incidence by acyclovir treatment.

Iris atrophy was observed in 7% of all study patients. It was not observed before three months follow-up and presented at a mean time of 206 days after entry into the trial. Four of five patients in whom it occurred also experienced anterior uveitis. No patient developed secondary cataract,

vitritis, retinitis, optic neuritis, extraocular muscle palsies, or contralateral hemiparesis during the period of observation. No significant differences in intraocular pressure were observed between acyclovir and placebo treated patients. Four patients followed beyond three months had HZO-related reduction in visual acuity to 20/100 or worse (5.6%). The one acyclovir treated patient in this group developed corneal scarring as a consequence of stromal keratitis and anterior uveitis. Three other patients, placebo-treated, developed visual loss due to posterior scleritis (two patients) and neurotrophic corneal ulceration (one patient). Pain persisted beyond three months in 41% of acyclovir treated and 35% of placebo treated patients with post herpetic neuralgia.

HZ KERATITIS Frequency (%)

Usual onset

TREATMENT (REVIEW OF CASE STUDIES)

Acute HZO (1 week): oral antiviral (Famvir or Valtrex) + topical steroid + topical antibiotic

Late HZO (> 1 week):topical steroid + topical antibiotic

Among respondents who chose to treat with topical corticosteroids, the most common choice of corticosteroid and dose was 1% prednisolone acetate 4 times a day (55 of 97, 57%),

punctate epithelial keratitis 50 2 days keratoconjunctivitis was established. A 7-day course of oral acyclovir (800 mg/day) along with topical prednisolone acetate 1% and moxifloxacin

early pseudodendrites – stain with rose Bengal not fluorescein, tapered ends, raised not ulcerated

50 4-6day Generally self-limited and treated with lubrication with artificial tears or ointment. May respond to topical antiviral agents (e.g. vidaribine ointment or ganciclovir gel,) especially if the pt is immunocompromised.

anterior stromal infiltrates 40 10days Topical steroid

keratouveitis/endotheliitis 34 7 days Topical steroid and nonprostaglandin antiglaucoma drop

serpiginous ulceration 7 1 mo Antibiotic, late topical steroid

sclerokeratitis 1 1 mo Topical steroid and Oral NSAID for scleritis

Corneal mucous plaques 13 2-3mos Full dose oral antivirals or topical vidaribine or TFT may or may not succeed.

Disciform keratitis 10 3-4mos Topical steroid

neurotrophic keratopathy (and persistent epithelial defects can lead to perforation)

25 2 mos Lubrication, antibiotic, surgical

exposure keratopathy 11 2-3mos Lubrication, antibiotic, surgical

Interstitial keratitis/lipid keratopathy

15 1-2 yrs 1-month course of prednisolone acetate,1%, starting at 4 times per day

Permanent corneal edema 5 1-2yrs Topical steroid, surgical

Herpes Zoster Complications include:

1. Ramsay Hunt Syndrome– 7th CN, facial muscle weakness, loss of taste in anterior 2/3rds of tongue and vesicles in the external auditory canal or pinna.

2. Acute Retinal Necrosis – potentially blinding condition which can occur due to VZV, HSV, or CMV in otherwise normal patients. May begin with anterior uveitis, and progress to include retinal arteritis, perivascular sheathing, necrotizing retinitis (peripheral retinal whitening which progresses over several days, active retinitis lasting 4 to 6 weeks during which an exudative RD may occur), vitritis, rhegmatogenous RD (75%), NVD/NVE.

3. Progressive Outer Retinal Necrosis – reported in HIV patients—multifocal, patchy choroidal and deep posterior retinal opacification that may initially be parafoveal. There is an absence of vitreous or anterior chamber reaction or signs of active vasculitis. Progresses rapidly from the posterior pole to involve the entire retina.

Other important points:

The development of Zoster in healthy young adults should raise suspicion of HIV

Whether it occurs early or late in the pregnancy, Herpes Zoster appears to have no deleterious effects on either the mother or the infant.

References

PHN is the leading cause of suicide in patients older than 70 years of age with chronic pain

Albert and Jacobiec, Pavan-Langston, Krachmer’s Cornea, Sundmacher’s Color Atlas of Herpetic Eye Disease, Rapuano’s Wills Eye Cornea, Habif’s Clinical Dermatology, Zajac and Harrington at UAB