For fluorescein evaluation, what lighting condition is recommended?

• A. Bright white light
• B. Dark room with cobalt light
• C. Red light
• D. UV light

Answer: (B)

Fluorescein evaluation relies on blue light to excite the dye and reveal staining with high contrast. Cobalt blue illumination provides the specific excitation wavelength that makes fluorescein emit a bright yellow-green glow, which is easily seen when the room is dark. The dark environment minimizes ambient glare and background light, so even small corneal defects or tear film breaks become clearly visible. Bright white light washes out the fluorescence, red light doesn’t excite fluorescein, and UV light is not the standard practical option for this exam. That combination—dark room with cobalt blue light—offers the best visualization of stained areas.