Clinical Comparison of Fusarium Keratitis according to the Initial Potassium Hydroxide (KOH) Smear: A Retrospective Study in South Korea

PURPOSE: This study aimed to compare predisposing factors, clinical characteristics, treatment, and prognosis of Fusarium keratitis according to the result of the initial potassium hydroxide (KOH) smear. METHODS: This is a retrospective study of cases with Fusarium keratitis between January 2000 and December 2019 at two tertiary hospitals in South Korea. Patients were divided into two groups depending on the KOH smear result (KOH-positive and KOH-negative group), and its clinical factors were analyzed. RESULTS: Among 319 fungal keratitis, seventy-nine cases were identified with Fusarium keratitis. Forty-seven cases (59.5%) were negative in the initial KOH smear prior to their diagnosis. The most common predisposing factor for Fusarium keratitis was ocular trauma (55.7%). There were no significant differences in sex, occupation, ulcer size or shape, hypopyon, and initial visual acuity between the two groups. Differences were observed between the KOH-positive group and the KOH-negative group in terms of deep corneal infiltration (50.0% vs. 78.7%, p=0.008) and evisceration treatment (3.1% vs. 25.5%, p=0.008). The delayed time to initiate antifungal eye drops was longer in the KOH-negative group (1.13 ± 0.49 vs. 3.93 ± 4.89, p=0.002). Only the KOH-negative group combined bacterial infection. The significant risk factors for poor clinical outcomes were the central corneal lesion (odds ratio (OR) 3.50, p=0.047), a large ulcer size (size ≥ 7.5 mm(2)) (OR 4.98, p=0.009), and endothelial plaque (OR 7.00, p=0.031). CONCLUSION: Initial KOH-negative patients often needed evisceration and had worse final visual outcomes. The delay of prompt initiation of antifungal treatment and combined bacterial infection result in a poor prognosis. This study highlights the initial KOH effect on early diagnosis and early treatment of Fusarium keratitis.