Characteristics and outcome of microsporidial keratitis

Abstract Purpose Microsporidia are a diverse group of obligate, intracellular, eukaryotic, spore-forming fungi like and not typical true fungi. Ocular manifestations vary from early to late stages of infection and include keratoconjunctivitis, stromal keratitis, scleritis, and rarely endophthalmitis. It is rarely reported in ophthalmology literature. The purpose of this study is to evaluate the characteristics and outcome of 26 cases of microsporidial keratitis. Methods We retrospectively reviewed the medical records of 26 immunocompetent patients with microsporidial keratitis presented in the period between 2007 and 2024. The inclusion criteria were all patients with confirmed diagnosis of microsporidial keratitis based on the clinical symptoms and confirmation of diagnosis that was done by microscopic identification of microsporidial organisms in corneal or conjunctival scrapings. Results The study included 26 patients (mean age: 39 years), with a male predominance (65%). Most were initially misdiagnosed, with epithelial or bacterial keratitis being the most common preliminary diagnoses. The most frequent presentation was diffuse epithelial keratitis (58%), followed by stromal infiltrates and keratoconjunctivitis. Notably, 53% of patients had a history of topical steroid use, and 23% reported prior application of unsterile topical honey. Visual acuity at presentation varied, with 27% presenting at 20/200 or worse. Visual outcomes improved over time, with patients presenting with diffuse epithelial keratitis showing the most favorable recovery. Stromal and disciform keratitis presentations were associated with poorer visual outcomes at 1 month. Conclusion Microsporidial keratitis is frequently misdiagnosed, leading to delayed treatment. Diffuse epithelial keratitis was the most common presentation and associated with better visual outcomes, while stromal involvement correlated with poorer prognosis. Early diagnosis and appropriate management are essential to optimize visual recovery.