Sodium fluorescein can not be used with hydrogel lenses because the lenses will absorb the fluorescein. A high molecular weight fluorescein (FluorSoft) was developed to use with soft lenses, but with todayΓÇÖs lens designs it is not very useful (because the thin lenses used today conform so closely to the ocular surface).
If a soft lens does absorb fluorescein most of it will diffuse out over time. We try to avoid getting too much fluorescein in the lenses as it may permanently yellow them.
