What are the key clinical features to differentiate between viral and bacterial keratitis in a primary care setting?

In a primary care setting, accurate differentiation between viral and bacterial keratitis typically requires specialist ophthalmological assessment, including slit-lamp examination NICE CKS. For suspected ocular herpes simplex infection, a form of viral keratitis, all cases should be referred to eye casualty or an emergency eye service for same-day assessment and specialist management NICE CKS. The guidelines emphasize that delayed diagnosis, misdiagnosis, or inappropriate treatment can lead to serious and/or sight-threatening sequelae NICE CKS. For instance, inappropriate use of topical or systemic corticosteroids in primary care may transform a simple herpetic dendritic ulcer into an extensive amoeboid ulcer, potentially causing corneal scarring and visual loss, and can aggravate infections caused by other pathogens NICE CKS. Therefore, specific clinical features for primary care differentiation are not detailed, with the emphasis placed on prompt specialist referral for diagnosis and management NICE CKS.