What dilution is recommended when using rose bengal stain to avoid damage to an ulcerated cornea?

• A. 0.1%
• B. 0.5%
• C. 1%
• D. 2%

Answer: (B)

The key idea is that rose bengal can be irritating to living corneal tissue, so when the cornea is ulcerated you want enough stain to reveal damaged areas but not so much that it further harms the epithelium. Diluting rose bengal to about 0.5% provides a balance: it stains devitalized cells and mucin to show ulceration, while reducing toxicity to the already compromised epithelium. In practice, you dilute the stock solution to 0.5% with sterile saline and apply only a small amount. Using a higher concentration increases the risk of additional epithelial injury and delayed healing, while a much lower concentration may stain too faintly to be useful.