An epithelial defect that is proportional to the size of the underlying infiltrate is more indicative of which type of ulcer?

• A. Mixed Ulcer
• B. Nonulcer Etiology
• C. Infectious Ulcer
• D. Sterile Ulcer

Answer: (C)

The key idea is how the surface damage relates to the underlying inflammation. In infectious keratitis, the processes that cause tissue loss—microbes and the accompanying neutrophilic inflammation—progress together. As the infiltrate (the area of stromal infection and inflammatory cells) grows, the epithelial cells over that same region are lost, so the epithelial defect enlarges proportionally to the infiltrate. That tight, proportional relationship is a hallmark of an infectious ulcer.

In contrast, sterile or noninfectious ulcers often have a disproportionate pattern: you may see a sizable epithelial defect with little or no stromal infiltration, or defects that don’t closely track the extent of inflammation. Mixed ulcers can blur this, but the proportional defect to infiltrate remains a clue toward an infectious process.

So, when the epithelial defect size mirrors the underlying infiltrate, infectious ulcer is the most likely explanation.