Hydroxypropyl cellulose (HPC) is an ether of cellulose where some of the hydroxyl groups of the cellulose have been hydroxypropylated. Hydroxypropyl cellulose is used as an excipient, and topical ophthalmic protectant and lubricant. Hydroxypropyl cellulose, manufactured by Aton Pharma, is a formulation of HPC used for artificial tears. It is used to treat medical conditions characterized by insufficient tear production such as keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure, and neuroparalytic keratitis. HPC is also used as a lubricant for artificial eyes. Hydroxypropyl cellulose acts to stabilize and thicken the precorneal tear film and prolong the tear film breakup time which is usually accelerated in patients with dry eye states. Hydroxypropyl cellulose usually reduces the signs and symptoms resulting from moderate to severe dry eye syndromes, such as conjunctival hyperemia, corneal and conjunctival staining with rose bengal, exudation, itching, burning, foreign body sensation, smarting, photophobia, dryness, and blurred and cloudy vision. Progression visual deterioration which occurs in some patients may be retarded, halted, or sometimes reversed.