What does fluorescein staining indicate in a corneal ulcer?

What does fluorescein staining indicate in a corneal ulcer?

• A. An epithelial defect is present
• B. Endothelial edema
• C. Deep stromal scarring
• D. Iris atrophy

Answer: (A)

Fluorescein staining shows where the corneal surface epithelium is missing. When the epithelium is intact, fluorescein stays in the tear film and doesn’t stain the cornea. If there’s a breach in the epithelial layer—as in a corneal ulcer—the dye penetrates to the underlying tissue and, under cobalt blue light, lights up the exposed area bright green. This makes the epithelial defect visible and helps measure its size. Endothelial edema involves swelling behind the epithelium, not a surface break, so fluorescein staining isn’t the primary sign there. Deep stromal scarring is scar tissue within the stroma, not an active epithelial defect. Iris atrophy affects the iris, not the corneal surface, so it wouldn’t be indicated by fluorescein staining of the cornea.

Fluorescein staining shows where the corneal surface epithelium is missing. When the epithelium is intact, fluorescein stays in the tear film and doesn’t stain the cornea. If there’s a breach in the epithelial layer—as in a corneal ulcer—the dye penetrates to the underlying tissue and, under cobalt blue light, lights up the exposed area bright green. This makes the epithelial defect visible and helps measure its size.

Endothelial edema involves swelling behind the epithelium, not a surface break, so fluorescein staining isn’t the primary sign there. Deep stromal scarring is scar tissue within the stroma, not an active epithelial defect. Iris atrophy affects the iris, not the corneal surface, so it wouldn’t be indicated by fluorescein staining of the cornea.