Investigating the seasonality of infectious keratitis by pathogen: A retrospective study

Abstract This study aimed to investigate the seasonal trends in infectious keratitis by assessing the month of onset and causative microorganisms. Five hundred consecutive cases of infectious keratitis that were diagnosed and treated by a corneal specialist at the Department of Ophthalmology, Yamaguchi University Hospital between January 2009 and January 2021 in whom micro-organisms could be identified formed the study population. The month of onset of infectious keratitis was retrospectively examined based on the medical records. The causative microorganisms were bacteria in 249 eyes, fungi in 51 eyes, Acanthamoeba in 27 eyes, and viruses in 173 eyes. The top 10 causative microorganisms accounted for 402 of 500 eyes (80.4% of the total). The incidence of infectious keratitis was highest from January to March and lowest in June. The total number of bacterial-induced infections was high between October and March. Pseudomonas aeruginosa commonly caused infectious keratitis from August to September. Acanthamoeba-induced infection was common in summer from June to August. HSV infections were common between January and May. A seasonal trend was observed in the occurrence of infectious keratitis by examining the months of onset. We contemplate that these results will assist ophthalmologists in diagnosing infectious keratitis.