Epidemiology
Fungal keratitis is primarily seen in tropical climates,probably due to the wind, higher temperatures and amount of rainfall. The incidence of fungal keratitis ranges between 6% and 67% of all microbial keratitis cases, depending on geographical location, and represents 30% to 40% of all cases of culture-positive infectious keratitis. In Australia, filamentous fungi accounted for 3% of corneal scrape results compared to 33% in India.
Moreover, fungi have replaced bacteria as the predominant cause of infectious keratitis in developing countries. In epidemiological meta-analyses the highest proportions of fungal infections were found in studies from India and Nepal.
The frequent use of ocular cortico steroids, and the increase in immuno compromised patients, have resulted in a rise in the incidence of fungal keratitis. Filamentous fungi are the major aetiological agents and Aspergillus species are the most common cause of fungal infection worldwide, especially in tropical climates, reported as 24%to 30% in some studies. Aspergillus is a ubiquitous filamentous fungus, commonly isolated from soil, plant debris and indoor and outdoor air. As with other filamentous fungi,most cases of Aspergillus keratitis have a history of trauma, particularly with vegetable matter.
In Cairo, increases in the frequency of fungal keratitis correlated significantly with rises in minimum temperature and the maximum atmospheric humidity, suggesting global climate change as an additional factor contributing to the increase of fungal keratitis worldwide.