Microsporidial keratitis: Global epidemiology, pathogen spectrum, and management

Microsporidial keratitis (MK) is an emerging ocular infection with a markedly increasing global incidence, particularly in Asia. To elucidate its global epidemiology, pathogen spectrum, and clinical management, this study systematically reviewed 76 relevant articles published between 1990 and 2025. Our analysis revealed distinct geographical clustering, with the highest disease burden reported in India, Thailand, Singapore, and China. Patient profiles exhibited a striking phenotypic divergence: superficial microsporidial keratoconjunctivitis (MKC) predominantly affected younger males and was strongly driven by environmental exposures or trauma. In contrast, the more severe microsporidial stromal keratitis (MSK) was frequently associated with older females and underlying systemic immunodeficiency. Etiologically, Vittaforma corneae emerged as the predominant pathogen across phenotypes. Opportunistic infections, specifically linked to severe immunosuppression, were primarily attributed to other species, such as Encephalitozoon hellem and Encephalitozoon cuniculi. Diagnostic yields from corneal scraping with staining, polymerase chain reaction, and corneal biopsy varied significantly depending on the clinical presentation. Therapeutically, MKC typically responded well to topical antimicrobials, whereas deep MSK frequently necessitated surgical intervention, primarily therapeutic penetrating keratoplasty. This systematic review consolidates the current understanding of MK, providing an evidence-based framework for its targeted prevention, risk stratification, and individualized treatment.