A 65-year-old farmer presents two days after a trivial ocular injury with soil-contaminated fingers. There is a dense yellowish-white central corneal ulcer with a sharply defined advancing edge that spreads like a serpent, heaped-up epithelium at the margin, marked circumcorneal congestion, and a 2 mm hypopyon. Which organism classically produces this 'ulcus serpens'?

• A Streptococcus pneumoniae ✓
• B Aspergillus fumigatus
• C Pseudomonas aeruginosa
• D Staphylococcus aureus

Explanation

The pneumococcal hypopyon ulcer is the textbook ulcus serpens: a central oval ulcer with a serpiginous advancing edge, heaped epithelium, and sterile hypopyon, typically after trivial trauma in an elderly rural patient. Pseudomonas produces a more rapidly sloughing, necrotic ulcer with greenish discharge rather than a discrete serpiginous edge with heaped borders.

Reference: Parsons' Diseases of the Eye, 22nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.