Case Report: Confocal microscopy in the early diagnosis of microsporidial keratitis.

This report describes a rare case of microsporidial stromal keratitis (MSK) complicated by corneal perforation in a 69-year-old male farmer with a 5-month history of ocular redness, pain, photophobia, and epiphora. In vivo confocal microscopy (IVCM) revealed pathognomonic findings-hyperreflective double-walled spore casings and vesicular clusters, providing the earliest diagnostic clues for microsporidia infection. Subsequent metagenomic next-generation sequencing (mNGS) and histopathology confirmed Microsporidia species. The patient underwent therapeutic penetrating keratoplasty followed by targeted anti-microsporidial therapy, achieving globe preservation and visual improvement. This case underscores IVCM's pivotal role in diagnosing MSK, particularly in atypical presentations. Because MSK remains a rare corneal disorder, its insidious progression necessitates high clinical vigilance. In summary, IVCM's ability to detect microsporidial structures in real-time significantly enhances early diagnosis, complementing molecular methods like mNGS. We conclude that IVCM, as a non-invasive and rapid diagnostic tool, provides a convenient and efficient means for the early differentiation of challenging corneal infections.