Material and Method: A retrospective analysis of 19 eyes in 15 patients referred to Siriraj Hospital between 2004 and 2010.

Results: Multifocal intrastromal infiltration, with relatively quiet ocular reaction and mild inflammation were initially presented in all eyes. They all previously had been diagnosed of presumed viral keratitis, and had been given topical corticosteroid treatment for a prolonged period of time without healing. Autoimmune disease workups were all negative. Corneal scrapings showed negative culture results in all eyes. However, bacteria within stromal lamellae with absent or minimal inflammatory cells were demonstrated in all eyes by corneal biopsies. In addition, cytology results obtained from 16S rDNA sequencing revealed Stenotrophomonas maltophilia in one eye and coagulase-negative staphylococci in two eyes. No case responded well to intensive topical and systemic antibiotics. However, they were successfully treated with penetrating keratoplasty (11 eyes, 57.9%) or intrastromal antibiotic injections (8 eyes, 42.1%).

Conclusion: Bacterial infection should be a concern in prolonged chronic IK. This was considered as primary bacterial IK or bacterial superinfection in immunocompromised cornea. Early recognition and appropriately aggressive managements contribute to successful outcome. Corneal biopsy is always essential and 16S rDNA sequencing is useful in this distinct clinical entity.

Keywords: Steroid modified keratitis, Interstitial keratitis, Bacterial keratitis