In a review and analysis of fungal keratitis diagnostic literature, investigators estimated the annual global incidence of fungal keratitis at over 1 million cases. The results of this analysis were published in The Lancet Infectious Diseases. The authors also found that 8% to 11% of cases resulted in the removal of an eye.
Fungal keratitis is a severe corneal infection that frequently affects young agriculture workers of low socioeconomic status. Investigators conducted a systematic literature review on the epidemiology of the disease. Of 397 records selected for full-text assessment, 118 provided incidence of fungal keratitis as a proportion of microbial keratitis and 18 included incidences in a defined population.
The global annual incidence was estimated to be 1,051,787. With an error rate of 30%, the range of infections is between 736,251 to 1,367,323 cases annually. The highest estimated incidence occurred in Asia and Africa and the lowest was in Europe. The mean proportion of culture-negative microbial keratitis in the analysis was 40.8% (14,024 of 34,257 cases) and ranged from 5% in Sierra Leone to 74.4% in Thailand.
If culture-negative cases were assumed to be fungal, the annual incidence increased to 1,480,916 cases (range, 1,036,641-1,925,191). The proportion of keratitis cases attributed to fungi varied. Among 37 countries where estimates were available, proportions ranged from 1.0% in Spain to 60.0% in Vietnam. Countries with greater than 25% of cases attributed to fungi tended to be near the equator but this was not universal.
Ocular outcomes were described in 4 case series from Pakistan, east Africa, Germany, and the United Kingdom. Reports of final vision being worse than 6/60 were 59% of eyes in Pakistan and 66% of eyes in east Africa. Eviscerations were needed in 11% of patients from Pakistan and 8% from east Africa. Another 30% of cases in east Africa resulted in corneal perforations.
Even in Germany, a high-resource setting, penetrating keratoplasty was performed in 57% of cases and enucleation in 9% of cases. In the United Kingdom, 20% of eyes became blind and 56% of eyes were left with good vision.
Using this data, investigators estimate 94,753 to 115,810 eyes are surgically removed each year, with more eyes being removed in countries with suboptimal eye care. They also predict that 610,821 eyes will become blind each year due to fungal keratitis.
Common limitations were the use of traditional microbiological methods to diagnose microbial keratitis, the possibility that many people in rural settings with fungal keratitis may never present to healthcare professionals, and that most studies took place at tertiary healthcare facilities.
Fungal keratitis is treatable with early diagnosis and generic antifungal therapy, said investigators. This condition is likely to affect over 1 million people worldwide annually, which demonstrates the need for a point-of-care diagnostic method and global availability of affordable treatments, concluded investigators.
Brown L, Leck AK, Gichangi M, Burton MJ, Denning DW. The global incidence and diagnosis of fungal keratitis. Lancet Infect Dis. Published online October 22, 2020. doi:10.1016/S1473-3099(20)30448-5