Recurrent herpes simplex keratitis

Herpes simplex keratitis (HSK) is caused by HSV type 1 in adults and is one of the most common infectious etiologies of blindness. It is second only to trauma as a cause of corneal blindness in the United States, where an estimated 50,000 new or recurrent cases are seen each year. Recurrent HSK can be reactivated by many factors in addition to those listed above. Reactivation has been reported in patients after penetrating keratoplasty, argon laser trabeculoplasty, Nd YAG laser peripheral iridotomy, or treatment with excimer lasers, including cases in which ocular herpes had not occurred previously. It is important to realize that because most patients have latent HSV it is possible for a reactivation to occur despite a negative history of a primary infection. 

Herpetic Eye Disease Study Group. Predictors of recurrent herpes simplex virus keratitis. Cornea 2001 20(2) 123-128. 

Vidarabine is used mainly in human HSV-1 and HSV-2 encephalitis, decreasing the mortality rate from 70 to 30%. Whitley et al. (57) reported that early vidarabine therapy is helpful in controlling complications of localized or disseminated herpes zoster in immunocompromised patients. Vidarabine also is useful in neonatal herpes labialis or genitalis, vaccinia virus, adenovirus, RNA viruses, papovavirus, CMV, and smallpox virus infections. Given the efficacy of vidarabine in certain viral infections, the U.S. FDA approved a 3% ointment for the treatment of herpes simplex keratoconjunctivitis and recurrent epithelial keratitis, and a 2% IV injection for the treatment of herpes simplex encephalitis and herpes zoster infections (Table 43.3). A topical ophthalmic preparation of vidarabine is useful in herpes simplex keratitis but shows little promise in herpes simplex labialis or genitalis. The monophosphate esters of vidarabine are more water-soluble and can be used in smaller volumes and even intramuscularly. These esters are under clinical investigation for the treatment of hepatitis B, systemic and cutaneous herpes simplex, and herpes zoster virus infections in immunocompromised patients. 

Primary keratoconjunctivitis and recurrent epithelial keratitis caused by herpes simplex virus types 1 and 2. 

Herpesviruses range in size from 120 to 300 nm and have DNA genomes and outer lipid membranes (envelopes). As enveloped viruses, herpesviruses are sensitive to drying and adverse conditions. Herpesviruses are spread by inoculation of susceptible mucous membranes or direct cell-to-cell contact. Over 100 herpesviruses have been identified, but only 5 cause human eye infections with any frequency herpes simplex virus-1 (HSV-1), herpes simplex virus-2 (HSV-2), varicella zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus. Herpesviruses can cause blepharitis, conjunctivitis, epithelial and stromal keratitis, uveitis, retinitis, and ARN. HSV-1 is the most frequent cause of primary and recurrent eye disease. The host immime system influences the rates of reactivation. Immimocompromised patients tend to have more frequent reactivations and more severe disease manifestations. The strain of virus also affects the... 

Trifluridine, an antiviral agent (1 drop of 1% solution onto the cornea), is nsed every 2 honrs while awake until the corneal nicer has reepithelialized completely. Trifluridine is indicated for primary keratoconjnnctivitis and recurrent epithelial keratitis dne to herpes simplex virus types 1 and 2. In addition, it is nsed for epithelial keratitis that has not responded clinically to topical idoxnridine, or when ocular toxicity or hypersensitivity to idoxnridine has occurred. 

Vidarabine, an antiviral agent (10 to 15 mg/kg/day for 5 to 10 days), is indicated in the treatment of herpes simplex virus encephalitis, neonatal herpes simplex virus infections, and herpes zoster in immunosuppressed patients. In addition, vidarabine (ophthalmic ointment 3% vidarabine monohydrate [equivalent to 2.8% vidarabine]) is indicated in the treatment of acute keratoconjunctivitis and recurrent epithelial keratitis due to herpes simplex virus types 1 and 2, or superficial keratitis caused by herpes simplex virus that has not responded to topical idoxuridine or when toxic or hypersensitivity reactions to idoxuridine have occurred. 

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