How can contact lens deposits result in reduced oxygen permeability?

With standard hydrogel lenses, oxygen transmission is achieved by the water content of the lens. Water absorbs atmospheric oxygen and cornea absorbs oxygen from this water (diffusion).
Unlike RGPs, soft lenses don't depend on microscopic "pores" to directly let atmospheric oxygen come in contact with cornea. Logic suggests, as long as these hydrogels are kept properly hydrated, oxygen permeability should not be reduced.

GPC, allergies, and risk of infections increase with prolonged use, fairly logical.
But how on earth can oxygen permeability reduce with build-up of proteins?

Could someone please explain?

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