Herpes Simplex Keratitis

Herpes simplex keratitis is a common and potentially blinding condition caused by recurrent corneal infections with the herpes simplex virus (HSV). Herpes simplex keratitis remains the leading infectious cause of corneal ulcers and blindness worldwide. The most ubiquitous types of HSV are HSV-1 and HSV-2, which affect humans, their only natural hosts. HSV-1 is usually the cause of infections in the oral, labial, and ocular areas; HSV-2 primarily causes lesions in the genital region, although this epidemiology is now changing. Primary infection with HSV occurs after direct contact inoculation of mucosal or skin surface, often subclinical and going unnoticed. After the initial HSV infection, the virus becomes latent, traveling to the dorsal root ganglia and remaining there for the person's lifetime. Subsequent infection is caused by viral reactivation in the affected dermatome.  Herpes simplex keratitis can result from primary HSV ocular infection or recurrent infection. After the initial infection in the ocular area, the virus travels to the trigeminal ganglion via the first branch of the trigeminal nerve (V1), remaining latent. HSV travels back to the cornea when reactivated, inciting an inflammatory response. The conjunctiva, cornea, anterior, iris, lens, vitreous, and retina may be involved. HSV recurrence within the cornea causes herpes simplex keratitis. Manifestations of herpes simplex keratitis include herpetic dendrites, geographical ulcers, stromal keratitis, disciform keratitis, and neurotrophic keratopathy, with herpetic stromal keratitis being the most common. Corneal inflammation can cause reduced corneal sensation, scarring, and blindness. Additionally, HSV infection can result in anterior uveitis, iridocyclitis, complicated cataracts, vitritis, and retinal detachment, which can quickly progress to corneal perforation or blindness if left unchecked.  Initially, herpes simplex keratitis is clinically diagnosed, including a meticulous slit lamp evaluation. Although polymerase chain reaction assay (PCR), enzyme-linked immunosorbent assay, and immunofluorescent antibody assay are additional studies that may be performed for diagnostic confirmation, a viral culture is the gold standard. Treatment with topical antibacterials, antivirals, and systemic antivirals aims to restrict viral replication, reduce lesion severity, and prevent further spread.