Herpes simplex virus in the human cornea

Herpes simplex virus (HSV) infection is prevalent throughout the world. An estimated 60–70% of children aged 5 and close to 90% of adults exhibit seropositivity (neutralising antibody) to HSV antigens. Despite this widespread prevalence, only 20%–30% present with clinical disease, and ocular manifestations develop in less than 1%.1

Traditionally, the diagnosis of herpes simplex keratitis (HSK) has been based on clinical evaluation, occasionally complemented by viral culture. Immunohistology and, relatively recently, polymerase chain reaction (PCR) and in situ hybridisation (ISH) techniques have been employed to detect viral DNA in corneal buttons removed at the time of penetrating keratoplasty or in corneal biopsy specimen taken from patients with undetermined corneal inflammation.2-7 The deployment of these techniques, however, has largely been as part of studies or projects, rather than a routine clinical service. The sensitivity and specificity of these techniques is variable and the detection of viral DNA does not necessarily correspond with presence of infective virus, as only a part of the viral DNA may be present. Only viral culture is 100% specific, but its …