VIRAL DISEASES

HERPES SIMPLEX

The most common manifestation of herpes simplex is fever blisters on the lips. The most common and serious eye lesion is keratitis (see Chapter 6). Vesicular skin lesions can also appear on the skin of the lids and the lid margins. Herpes simplex may cause iridocyclitis and may rarely cause severe encephalitis.

There are two morphologic strains of the virus: type 1 and type 2. Ocular infections are usually produced by type 1, whereas genital infections are caused by type 2. Retinitis due to herpes simplex virus type 1 or 2 occurs in adults suffering from herpes encephalitis or in immunosuppressed patients. Severe occlusive retinal vasculitis develops, followed by retinal necrosis and detachment. Type 1 antigens have been found in all layers of the retina, pigment epithelium, and choroid. Intravenous acyclovir prevents spread of the disease, and prophylactic retinal buckling may be useful.

Varicella-zoster virus is usually implicated in acute retinal necrosis syndrome, which produces a similar clinical picture but affects healthy individuals. However, herpes simplex types 1 and 2 and cytomeg-alovirus, albeit rarely, are now also associated with this condition. A 3-month course of oral acyclovir reduces the chances of involvement of the second eye.

VARICELLA-ZOSTER (Chickenpox & Herpes Zoster)

First infection with varicella-zoster virus causes chickenpox (varicella). Swollen lids, conjunctivitis, vesicular conjunctival lesions, and (rarely) uveitis and optic neuritis may occur.

Herpes zoster is the response to the same virus in a partially immune person, ie, someone who has previously had chickenpox. It is usually confined to a single dermatome on one side and presents with malaise, headache, and fever followed by burning, itching, and pain in the affected area. The commonest ophthalmic manifestation is herpes zoster ophthalmicus, and the ocular complications are caused by ischemia, viral spread, or a granulomatous reaction. The acute stage is characterized by a virulent rash, conjunctivitis, keratitis, episcleritis, and uveitis when the nasociliary nerve is involved.

Treatment in the acute stages with high doses of oral acyclovir; 800 mg five times a day for 10 days, started within 72 hours after eruption of the rash, reduces ocular complications including postherpetic neuralgia. Anterior uveitis requires topical steroids and cycloplegics.

The acute retinal necrosis syndrome has been described following chickenpox and herpes zoster (see above). In immunocompromised individuals, both herpes zoster, which may become disseminated, and varicella are likely to be severe and may be fatal.

CYTOMEGALIC INCLUSION DISEASE

Infection with cytomegalovirus, also a member of the herpesvirus group, may range from a subclinical infection to classic manifestations of cytomegalic inclusion disease. The virus most frequently affects newborn infants and compromised hosts, and the disease can be acquired or congenital. The ocular findings in the newborn include focal necrotizing retinitis and choroiditis with perivascular infiltrates and retinal hemorrhages. Other reported ocular findings include microphthalmia, cataract, optic atrophy, and optic disk malformation.

Histopathologic examination of the retinal and choroidal lesion shows large inclusion-bearing cells characteristic of cytomegalovirus infections. There is disruption of the normal architecture of the retina and choroid, with evidence of necrosis and mononuclear and perivascular infiltration. Calcifications in the retina may be observed.

The differential diagnosis in the congenital disease should include toxoplasmosis, rubella, herpes simplex infection, and syphilis.

Ganciclovir is the drug of choice for cytomegalic inclusion retinitis. It halts the progression of the disease without eradicating the virus. (See section on AIDS, below.)

POLIOMYELITIS

Bulbar poliomyelitis severe enough to cause lesions of the third, fourth, or sixth cranial nerve is usually fatal. In survivors, any type of internal or external ophthalmoplegia may result. Supranuclear abnormalities ("gaze" palsies, paralysis of convergence or divergence) are rare residual defects. Optic neuritis is uncommon. Treatment is purely symptomatic, though occasionally a residual extraocular muscle imbalance can be greatly improved by strabismus surgery.

GERMAN MEASLES (Rubella)

Maternal rubella during the first trimester of pregnancy causes serious congenital anomalies. The most common eye complication is cataract, which is bilateral in 75% of cases. Other congenital ocular anomalies are frequently associated with the cataracts, eg, uveal colobomas, nystagmus, microphthalmos, strabismus, retinopathy, and infantile glaucoma. Congenital cataract, especially if bilateral, may require surgical removal, but the prognosis is always guarded.

MEASLES (Rubeola)

Acute conjunctivitis is common early in the course of measles. Koplik's spots may be seen on the conjunctiva, and epithelial keratitis occurs frequently.

The treatment of the eye complications of measles is symptomatic unless there is secondary infection, in which case local antibiotic ointment is used.

MUMPS

The most common ocular complication of mumps is dacryoadenitis. A diffuse keratitis with corneal edema resembling the disciform keratitis of herpes simplex occurs rarely.

INFECTIOUS MONONUCLEOSIS

The disease process can affect the eye directly, causing nongranulomatous uveitis, scleritis, conjunctivitis, retinitis, choroiditis, or optic neuritis. Complete recovery is usual, but residual visual loss can result.

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