Herpes ans Zoster Keratitis

Herpes simplex virus (HSV) and varicella‐zoster virus (VZV) are two leading causes of corneal infection with potential severely impaired visual acuity. These two viruses share multiple characteristics, including the ability to become latent in the trigeminal ganglia, before reactivation and migration along the trigeminal fibers innervating the cornea. The clinical settings of keratitis may vary from an epithelial defect (dendritic of geographic) to a more severe disease involving the stroma and/or the endothelium. Classically, HSV keratitis occurs from the second decade of life, and associated skin disease is not frequent and only involves the eyelids. In contrast, VZV keratitis mostly occurs after the sixth decade, as an associated finding of herpes zoster ophthalmicus (HZO). However, several studies recently highlighted that the rate of HSV keratitis increases with age, even in elderly, and some other studies reported VZV keratitis in children, either isolated or associated with HZO. Antiviral drugs currently available are highly efficient to reduce the severity on ongoing HSV‐ or VZV keratitis, but preventive treatments still have to be optimized. For HSV keratitis, the usual preventive treatment, as defined by the HEDS study, only reduces the rate of relapses in a two‐fold manner, and the optimal dosage has not been settled for patient with severe herpetic disease. For VZV, the two vaccines against chickenpox and HZO probably will lead in the future to a reduction of the incidence of keratitis, but they are not widely used, even in most of developed countries.