The invention relates to modified polysaccharide ethers having a weight-averaged molecular weight of 40000 to 50000 g/mole, zero shear viscosity of more than 10 Pas, and pseudoplasticity of more than 20, obtainable by reacting cellulose-based polysaccharide ether(s) with at least one mesogenic modification agent or modified polysaccharide ethers, obtainable by reacting polysaccharide ether(s) selected from the group consisting of hydroxypropylmethyl cellulose (HPMC), hydroxyethylmethyl cellulose (HEMC), methyl cellulose, and cellulose ethers with methyl and/or ethyl and/or propyl groups and mixtures thereof, with at least one mesogenic modification agent. Said substances can be used to produce gel-like to stable aqueous preparations having viscoelastic flow properties, which are suited for use in the human body, particularly within the scope of ophthalmologic procedures.