In bacterial keratitis testing, culture is indicated if the corneal ulcer is greater than how many millimeters in the visual axis?

• A. 1 mm
• B. 2 mm
• C. 3 mm
• D. 4 mm

Answer: (B)

In bacterial keratitis, the decision to culture hinges on how large the ulcer is in the visual axis. If the central corneal ulcer is larger than 2 millimeters in diameter, a culture is indicated to identify the causative organism and tailor antibiotic therapy, because larger central ulcers carry a higher risk of deeper infection and worse visual prognosis. Smaller ulcers can often be managed with empirical treatment, unless there are risk factors or the lesion isn’t responding to therapy. When culturing, measure the ulcer along the visual axis and obtain a corneal scraping after topical anesthesia for culture and, if possible, Gram stain to guide early management.