Fungal keratitis: Rapid diagnosis using methylene blue stain

Earlier and accurate diagnosis of the fungal infection in the cornea is necessary for effective treatment. In developing countries, microscopical evaluation is the most valuable and rapid diagnostic tool. Therefore we aimed to investigate the efficacy of methylene blue (MB) staining in comparison with potassium hydroxide (KOH) and calcofluor white (CW) stain. Corneal scraping from 48 cases with suspected fungal keratitis were included in the study from January 2014 to December 2014. The specimens were subjected to direct examination by MB, 10% KOH and CW stain. The staining results were confirmed with fungal culture and strain identification. Topical amphotericin B was started for all positive fungal cases; 39 (81.25%) were proven fungal cases. Positive rate of calcofluor white, MB and 10% KOH staining were 79.2%, 75% and 68.75% respectively. CW showed higher sensitivity and specificity (99.44% and 90.91% respectively), followed by MB (92.31% and 80.0% respectively) and lastly KOH 10% (84.62% and 71.43% respectively). 71.8% of cases had healed scars and only 4 patients (10.3%) required keratoplasty (PK). Direct microscopic detection of fungal structures by MB staining in corneal scrapes is a fast and effective method for the early diagnosis of fungal keratitis.