Fluorescein stains what structures?

Fluorescein stains what structures?

• A. Epithelium
• B. Exposed stroma
• C. Descemet's membrane
• D. Iris

Answer: (B)

Fluorescein reveals breaks in the corneal epithelial barrier. When the epithelium is intact, the dye stays in the tear film and is washed away, so you don’t see staining. If there is epithelial damage, the dye can reach the underlying stroma and pool there, making the exposed stroma light up bright green under blue light. That’s why the staining marks the areas of epithelial loss with exposed stroma. The iris and Descemet’s membrane aren’t stained because the dye doesn’t reach them through an intact surface or unless a very deep lesion is present, which is not the typical finding.

Fluorescein reveals breaks in the corneal epithelial barrier. When the epithelium is intact, the dye stays in the tear film and is washed away, so you don’t see staining. If there is epithelial damage, the dye can reach the underlying stroma and pool there, making the exposed stroma light up bright green under blue light. That’s why the staining marks the areas of epithelial loss with exposed stroma. The iris and Descemet’s membrane aren’t stained because the dye doesn’t reach them through an intact surface or unless a very deep lesion is present, which is not the typical finding.