Microbial keratitis in Sydney, Australia: risk factors, patient outcomes, and seasonal variation

Purpose To provide recent data on patient demographics, clinical profile and outcomes of patients with microbial keratitis over a 5-year period at the Sydney Eye Hospital, and to identify seasonal variations of the main causative organisms. Method A retrospective study of patients with a clinical diagnosis of microbial keratitis and corneal scrape performed between 1 January 2012 and 31 December 2016. Clinical information was gathered from medical records and pathology data. Results One thousand fifty-two eyes from 979 patients with a mean age of 54.7 +/- 21.5 years (range 18-100 years) were included. The majority of cases were bacterial (65%) followed by polymicrobial (2.4%), fungi (2.3%), and culture-negative (31%). Common risk factors for microbial keratitis were contact lens wear (63%) and previous topical steroid use (24%). Factors significantly associated with poor patient outcomes in the multivariate model were age, visual acuity, and epithelial defect size (p < 0.05). Patients with fungal or polymicrobial keratitis presented with worse clinical features at initial and final presentation (p < 0.05). There was a significant variation in the occurrence of Pseudomonas aeruginosa (p = 0.018) and fungal keratitis (predominately made up of Candida and Fusarium species) (p = 0.056) in the hottest seasons. Conclusion Poorer outcomes are more likely to be seen in older patients and those presenting with poor visual acuity and large epithelial defects at the initial presentation.