Fig. 2. A. A perforated cornea showing a positive Seidel test. Under cobalt blue light, the fluorescein does not radiate in the slit beam where it is quenched. In the lower portion of the beam where there is a bright reflection, the fluorescein is unquenched and glowing a bright yellow-green. B. A perforated cornea showing clear aqueous diluting unquenched fluorescein. (Courtesy Elmer Tu, MD.)