Comment on: Depth, size of infiltrate, and the microbe – The trio that prognosticates the outcome of infective keratitis

Dear Editor, In their interesting paper, Agarwal et al.[1] stress that the outcome of infective keratitis depends on the depth of involvement, infiltrate size, and the causative microbe. Similar observations have previously been reported, although on fewer patients.[2-5] To aid decision-making in managing microbial keratitis (MK), Jones advocated grading severity at presentation as “non-severe” or “severe,” based on ulcer diameter and depth, suppuration (infiltration) depth, and presence of perforation or scleral suppuration; that a severe ulcer had a higher risk of a poor outcome was inferred.[2] A 2006 study on fungal keratitis found that progressive worsening or perforation of the ulcer (despite maximal medical management) was associated with presenting infiltrate size >14 mm2, hypopyon, or Aspergillus culture growth.[3] In a prospective study in 2018 on severe MK (252 patients), presenting infiltrate size ≥5.2 mm2, posterior corneal involvement, and Aspergillus culture growth were significantly associated with poor outcomes.[4] In a recent retrospective cohort study, ≥1+ anterior chamber cells, ≥2 mm infiltrate, and infiltrate at ≤3 mm distance from the corneal center were independently associated with a vision-threatening outcome (perforation).[5] In the paper by Agarwal et al.,[1] the term “virulence of organism” should not have been used as virulence correlates (e.g., histopathology) were not studied. Instead, in the abstract, the authors should mention that “interplay between the microorganisms present, along with the depth and size of the infiltrate, determines the outcome of microbial keratitis.” This statement is validated by their observation that their Acanthamoeba infections mostly responded to medical management, whereas Pythium keratitis mostly required surgical involvement, irrespective of the size or depth.[1] Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.