Incidence of herpes simplex virus keratitis and other ocular disease: global review and estimates

Purpose: We aimed to review available data on the incidence of herpes simplex virus (HSV) keratitis and other HSV ocular disease and to estimate the global burden of HSV ocular disease. Methods: We searched Medline and Embase databases to October 2020 for studies reporting on the incidence of HSV ocular disease. Study quality was evaluated using a four-point checklist. Pooled estimates were applied to 2016 population data to estimate global HSV ocular disease burden. Numbers with uniocular vision impairment (any visual acuity <6/12) were estimated by applying published risks to case numbers. Results: Fourteen studies had incidence data; 7 met our quality criteria. In 2016, an estimated 1.7 (95% confidence interval, 95%CI 1.0-3.0) million people had HSV keratitis, based on a pooled incidence of 24.0 (95%CI 14.0-41.0; N=2; I2=97.7%) per 100,000 person-years. The majority had epithelial keratitis (pooled incidence 16.1 per 100,000; 95%CI 11.6-22.3; N=3; I2=92.6%). Available studies were few and limited to the USA and Europe. Data were even more limited for HSV uveitis and retinitis, although these conditions may collectively contribute a further >0.1 million cases. Based on global incidence, some 230,000 people may have newly acquired uniocular vision impairment associated with HSV keratitis in 2016. Conclusion: Over 1.8 million people may have herpetic eye disease annually. Preventing HSV infection could therefore have an important impact on eye health. Herpetic eye disease burden is likely to have been underestimated, as many settings outside of the USA and Europe have higher HSV-1 prevalence and poorer access to treatment.