Both microbiology and histopathology should be used to have the best chance of detecting infectious keratitis.
Both microbiology and histopathology should be used to have the best chance of detecting infectious keratitis. Photo: Suzanne Sherman, OD; Graham Lee, MD. Click image to enlarge.

Early identification of the causative organism in a patient who presents with a corneal infection is imperative to form the most effective treatment plan and avoid visually devastating outcomes. Despite it being the gold standard for diagnosing this condition, culturing of corneal scrapings is prone to erroneous results. Performing a corneal biopsy is a useful alternative diagnostic technique, as this modality is able to access deeper stromal infiltrates and tissue layers for microbial and histopathologic analysis. A recent study found that when used in tandem, microbiologic culture and histopathologic examination become more reliable methods to identify the microorganisms in corneal specimens causing presumed infectious keratitis.

The researchers retrospectively analyzed records from Bascom Palmer Eye Institute of patients who underwent corneal biopsy, therapeutic keratoplasty or endothelial graft removal for infectious keratitis at some point during a four-year period. Included specimens had also been bisected and submitted for evaluation with both microbiologic culture and histopathologic examination. Patient age ranged widely, from 23 days old to 95 years old (mean age: 59).

No organisms were identified in slightly more than half of the 213 corneal specimens (51%). The remaining 49% of specimens had organisms identified via microbiology and histology or both. Neither diagnostic method was shown to be superior to the other. Rather, the data revealed that the two techniques were complementary.

“Performing microbiology or histopathology alone would potentially miss 29% or 32% of causative organisms, respectively,” the researchers noted in their paper. They added that the detection of bacteria, fungus and mycobacteria was not statistically different between culture and histopathology.

The researchers concluded that performing both microbiological and histopathological analyses together may help increase the likelihood of microorganism detection compared with either modality alone.

Hudson J, Al-Khersan H, Carletti P, et al. Role of corneal biopsy in the management of infectious keratitis.Curr Opin Ophthalmol. June 16, 2022. [Epub ahead of print].