There are several "disappearing" preservatives currently popular in artificial tear products, including GenAqua (in the Genteal products), Purite (in Refresh and in Rx products by Allergan) and sodium perborate (in TheraTears).
The general concept with preservatives of this type is that the eyedrops are effectively preserved in the bottle but on contact with the eye (or on light exposure) the preservative is supposed to dissipate into basically oxygen and water.
While probably quite a bit safer than BAK-containing drops, tears with "disappearing" preservatives should not be considered equivalent to unpreserved tears. Some people have low tolerance for these preservatives. There is also some debate as to whether the "disappearing" action takes place as effectively on a very dry eye as on a healthy tear film.
Our advice: Discuss with your doctor whether regular use of products with GenAqua is acceptable for you and if so what is the maximum applications per day your doctor is comfortable with.