The use of poly(oxyethylene)-poly(oxybutylene) block copolymers in pharmaceutical compositions useful for modifying the surfaces of contact lenses and other medical devices is disclosed. The present invention is based in-part on a discovery that this class of compounds is particularly efficient in wetting hydrophobic surfaces, such as the surfaces of silicone hydrogel contact lenses and other types of ophthalmic lenses. Such compounds are also useful for cleaning purposes. The use of the compounds as surfactants in various types of compositions for treating contact lenses therefore represents a preferred embodiment of the present invention.