Glycerol is an osmotic dehydrating agent that possesses hygroscopic and lubricating properties. It causes plasma osmolality leading to the movement of water into the plasma from the extravascular spaces via osmosis. Hypromellose stabilises and thickens the precorneal tear film and prolongs the tear film breakup time thereby promoting corneal wetting. It also lubricates and protects the eye. Polyethylene Glyco: Ocular lubricant.