Seasonal Variation in the Presentation of Infectious Keratitis

Infectious keratitis is a common ophthalmic disease with the potential for severe ocular morbidity. Multiple studies have described various risk factors for the development of infectious keratitis. The purpose of this study was to analyze the seasonal variation in the presentation of infectious keratitis, and also seasonal changes in its etiologies and risk factors.

A retrospective chart review was performed on consecutive patients presenting to the emergency department at our tertiary care urban hospital center who were diagnosed with infectious keratitis from 2008 to 2013. A chi-square analysis was performed to determine whether a significant seasonal variation existed between the month, season, frequency of presentation of ulcers, and other risk factors.

A total of 155 patients-53 men and 102 women-with a mean age of 40 (range, 3-97; median, 36) diagnosed with infectious keratitis were included in the analysis. Sixty-nine (44.5%) ulcers presented in the summer, 19 (12.3%) in the fall, 34 (21.9%) in the winter, and 33 (21.3%) in the spring (P<0.0001). Seventeen (11%) patients experienced diabetes mellitus, 60 (39%) were contact lens wearers, 12 (8%) ulcers occurred in the setting of trauma, and 19 (12%) patients underwent previous ocular surgery. A total of 92 ulcers were cultured, of which 53.8% were positive in the summer, 42.9% in the fall, 55.0% in the winter, and 42.1% in the spring. A significant seasonal variation in the frequency of 1 organism, Pseudomonas aeruginosa, was identified (P=<0.0001); up to 47.6% of culture-positive ulcers in the summer were P. aeruginosa positive, whereas cultures in the remaining seasons were 0, 9.1% and 12.5% positive for this organism.

The summer months have a higher frequency of infectious keratitis and P. aeruginosa positivity in this study. Possible factors leading to this increased summer presentation include warmer temperatures, higher humidity, and greater ocular exposure to water. Clinicians should increase their vigilance and education to high-risk patients during these periods and potentially modify empiric treatment regimens.