Prophylactic treatment with oral antiviral agents appeared to dramatically decrease the recurrence of herpes simplex virus eye disease even while incidence remained stable, according to a long-term study of residents of one Minnesota county.
Using the Rochester Epidemiology Project (REP), Mayo Clinic researchers retrieved 694 records that contained diagnostic codes related to herpetic eye disease in residents of Olmsted County, Minn., between 1976 and 2007, Ryan C. Young and his colleagues reported. They found 394 confirmed cases (181 men, 213 women), with a mean age of onset of 43 years. Mean follow-up was 7.7 years.
After researchers eliminated nine patients identified as not county residents and adjusted for age and sex, they determined the incidence of new cases of herpes simplex virus (HSV) keratitis to be 9.2/100,000 resident per year during the study period and of ocular HSV to be 11.8/100,000 per year (Arch. Ophthalmol. 2010;128:1178-83). The incidence increased with age, with a peak at 28/100,000 people in the ninth decade of life, the researchers wrote.
In all, 169 patients experienced recurrence of ocular HSV, with an estimated likelihood of recurrence of 27% at 1 year after the initial episode, 50% at 5 years, 57% at 10 years, and 63% at 20 years, the researchers found.
Of those patients, 108 had a second recurrence, for a rate of 38% at 1 year, 67% at 5 years, 78% at 10 years, and 83% at 20 years. And 65 patients experienced a third recurrence, for a rate of 29% at 1 year, 65% at 5 years, 78% at 10 years, and 82% at 20 years.
Of 175 patients (44%) who received oral antiviral therapy for a mean period of 2.8 years, 4 experienced a first recurrence, 10 developed an epithelial recurrence, 20 had a stromal recurrence, and 3 developed blepharitis or conjunctivitis.
Oral antiviral prophylaxis decreased the relative risk of a first recurrence by a factor of 2.9, according to Cox proportional hazards models. Without prophylaxis, patients were 9.4 times more likely to have a recurrence of epithelial keratitis, 8.4 times more likely to have a recurrence of stromal keratitis, and 34.5 times more likely to have a recurrence of blepharitis or conjunctivitis.
A total of 20 patients experienced adverse outcomes, including vision loss, corneal perforation, enucleation, glaucoma surgery, keratoplasty, and conjunctival flap. Of these, 17 were not receiving antiviral treatment at the last recurrence before the adverse event, and 14 had never been treated prophylactically.
"The results of this study suggest that oral antiviral prophylaxis should be considered for patients with frequent recurrences of corneal disease," the researchers wrote. "We recommend an evaluation of the possible barriers preventing compliance with antiviral prophylaxis and a reassessment of the cost effectiveness of long-term oral antiviral therapy."
Strengths of the study included the large number of subjects, long-term follow-up, and use of a community-based cohort, according to the researchers. Potential weaknesses include lack of comparison before and after the introduction of prophylactic oral therapy, reliance on the accuracy and completeness of patient records, and lack of laboratory confirmation in most HSV cases.