Under normal circumstances, bacteria can reside in the conjunctival sac. Infection can occur when the pathogenicity of infecting bacteria is stronger than the host's defense capabilities, or when the host's defense capabilities are compromised. Patients with varying degrees of conjunctival hyperemia and purulent, mucoid, or mucopurulent secretions in the conjunctival sac should be suspected of bacterial conjunctivitis. Keratitis refers to the condition where the cornea's defense capabilities are reduced, and inflammation of the corneal tissue occurs due to external or endogenous pathogenic factors invading the cornea.