Wettability of materials is an important parameter for tolerance to contact lenses.
For contact lenses made from silicone rubber (hydrophobic material), it is difficult to achieve sufficient wettability of the material which is necessary in order to slip contact lens on the eye. These contact lenses need to incorporate a hydrophilic component. Worse wetting material can often be compensated by a high absorption capacity mucin of the tear film. This gives the ability to slip on the cornea.