A viscoelastic medium is useful for the manufacture of a medicament, such as a medical device, for treatment of increased intraocular pressure in the eye of a human or animal. The medicament is administerable into at least one sclerally penetrating fistula of the eye such that the fistula is filled with the medicament. The medium is also useful in a method of treating increased intraocular pressure in the eye of a human or an animal in need thereof, comprising the step of injecting the viscoelastic medium into at least one sclerally penetrating fistula in the eye such that the fistula is filled with the medium.