The epidemiology of nonviral microbial keratitis in a tertiary care center in Muscat, Oman

OBJECTIVE: The objective of this study is to describe the epidemiology, risk factors, etiology, and outcome of microbial keratitis in a tertiary care center in Muscat, Oman. METHODS: The electronic records of all patients diagnosed with keratitis or corneal ulcer between January 2013 and January 2016 in Al-Nahdha Hospital were retrospectively reviewed. Patients who presented with a corneal ulcer requiring admission and who underwent culture and sensitivity studies were included in the study. Patients with viral keratitis or sterile corneal ulcers were excluded from the study. RESULTS: A total of 606 electronic medical records of all presumed microbial keratitis were reviewed. Out of these, 304 met the eligibility criteria. The mean age of patients was 52.2 years (standard deviation [SD]: ±23.2 years; range: 0.1–89 years). A total of 198 (65%) microbial cultures yielded positive results. Of these, 182 (92%) were bacterial, 13 (7%) were fungal, and 3 (1%) cases were due to a combined (bacterial and fungal) etiology. Gram-positive bacteria accounted for 102 (55.1%), of which the majority was due to Streptococcus pneumoniae. Gram-negative bacteria accounted for 77 (41.6%) cases; half were caused by Pseudomonas aeruginosa. Keratitis in patients aged 18 years and younger was more likely to be associated with trauma (48.3%, P < 0.001) in young adults with contact lens wear (64%, P < 0.001) and in adults over 40 years with blepharitis (55.6%), sequelae of previous trachoma infection (26.3%), and eyelid abnormalities (18.4%). Following recovery, corneal scarring was seen in 63.2% of patients. CONCLUSION: Microbial keratitis affects patients of all age groups but is more common in older adults. The vast majority of culture-proven cases are due to bacterial infections. Children and teenagers are more likely to develop keratitis following eye trauma whereas young adults mostly develop the condition in association with contact lens wear. Ocular surface disease is the most important risk factor in older adults. The majority of patients end up with corneal scarring.