Gas permeable lenses and PMMA lenses will not absorb fluorescein, which is why it is perfectly safe to use fluorescein for hard and gas permeable contact lens fittings. However, soft contact lenses will absorb fluorescein, so it must be avoided unless the eyes are thoroughly rinsed with saline before soft contact lenses are reinserted.
A more convenient option for examining soft contact lens wearers is fluorexon disodium dye, which is a "Large Molecule" fluorescein which prevents absorption into all lenses, including soft contact lenses. Fluoresoft (PO-6360) is liquid fluorexon sold in individual ampules. Each box contains twenty single use 0.4 mL ampules.
For more information, please contact your Amcon Representative at 1-800-255-6161.