How is fluorescein stain best used?

• A. Just dab with diluted strip
• B. Just touch the strip (not diluted) to the sclera and then flush; evaluate the entire cornea in a dark room with a cobalt light +/- magnification; check nasolacrimal puncta patency (5-20 mins)
• C. Soak the strip before applying to the cornea
• D. Use a spray applicator to apply dye to the globe

Answer: (B)

Fluorescein staining is used to reveal corneal epithelial defects by highlighting areas where the corneal surface is disrupted. The dye binds to exposed stroma and fluoresces bright green under cobalt blue illumination, making ulcers or abrasions easy to see.

The best use involves applying a small amount of fluorescein with a moistened strip onto the ocular surface so the dye contacts the tear film and can identify defects. After application, remove excess dye so you don’t obscure findings, then examine the eye in a dark room using a cobalt blue light (and magnification if available). This setup lets you visualize the entire cornea and any staining patterns that indicate ulcers, depth, or involvement of the tear film.

In addition, assessing tear drainage by observing whether dye clears through the nasolacrimal puncta over several minutes provides information about patency that can affect healing and management. Waiting about 5–20 minutes for dye behavior in the tear film and drainage is a practical window to evaluate this.

Other application methods are less reliable: touching dry dye to the eye or to the sclera can yield poor or non-specific staining, soaking the strip can dull the signal, and spraying dye on the globe is not a controlled way to evaluate the corneal surface. The described approach—moistened strip application, thorough corneal examination under blue light, and assessment of punctal patency—offers the most accurate and useful assessment of corneal health with fluorescein.