title: A proposed mechanism for increased tear-film osmolarity in contact lens wearers.
abstract: Contact lenses decrease corneal sensitivity and increase tear-film osmolarity. To determine whether the decrease in corneal sensitivity is responsible for the increase in tear-film osmolarity, we studied tear-film osmolarity in normal rabbits and rabbits with surgically induced keratoconjunctivitis sicca before and after the instillation of 0.5% proparacaine. Instillation of proparacaine resulted in a significant increase in tear-film osmolarity. Decreased corneal sensitivity, with a resultant decrease in tear secretory rates, is the most likely cause for increased tear-film osmolarity in wearers of hard contact and extended-wear soft contact lenses.
mesh_terms: D000818:Animals; D003261:Contact Lenses / Q000009:adverse effects; D003263:Contact Lenses, Hydrophilic / Q000009:adverse effects; D006801:Humans; D007637:Keratoconjunctivitis / Q000503:physiopathology; D009994:Osmolar Concentration; D011430:Propoxycaine / Q000494:pharmacology; D011817:Rabbits; D012636:Secretory Rate / Q000187:drug effects; D013666:Tears / Q000378:metabolism / Q000502:physiology*
chemical_list: C005717:proxymetacaine; D011430:Propoxycaine