Ocular retention

Schoenwald et al. [280] demonstrated the unique ocular retention of this polymeric gel base in rabbits, in which the miotic effect of pilocarpine was significantly... 

Beilin, M., Bar-Ilan, A., and Amselem, S. (1995), Ocular retention time of submicron emulsion (SME) and the miotic response to pilocarpine delivered in SME. Investigative Ophthalmol. Vis. Sci., 36, S166. 

Like PVA, the viscosity enhancer hydroxypropyl methyl-cellulose is available in a variety of molecular weights and in formulations with different group substitutions. It has been shown to prolong tear film wetting time and to increase the ability of fluorescein and dexamethasone to penetrate the cornea. Hydroxypropyl methylcellulose 0.5% has been shown to exhibit twice the ocular retention time of 1.4% PVA. 

Although the cellulose ethers enhance viscosity and prolong the ocular retention time of solutions, they may also exert other effects that are less well imderstood. 

Use of preserved tear substitutes with contact lenses is a concern because the preservatives may bind to the lens polymer, prolonging ocular retention and exposure, which may result in toxic or hypersensitivity reactions. BAK is more readily absorbed than are thimerosal and chlorhexidine in most hydrogel lenses. 

Hydrogels Timolol maleate Ocular retention and sustained drug delivery [91]... 

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