title: Impact on ocular surface evaporation of an artificial tear solution containing hydroxypropyl guar.
abstract: OBJECTIVE
  To determine whether any acute effects on evaporative parameters are produced when using a solution containing Hydroxypropyl (HP) (Systane) versus normal saline solution in the eyes of patients with Keratoconjunctivis Sicca at 30 and 60 minutes postinstillation.
  
  
  METHODS
  Randomized double-blinded placebo-control 2-period cross-over clinical trial. Twelve patients with a clinical diagnosis of Keratoconjunctivis Sicca were enrolled in this study. Aqueous tear evaporation was measured at baseline, i.e., before the application of drops on the eye, and at 30 and 60 minutes after instillation of one 40 microL drop of either the HP-Guar containing drop or normal saline on two separate days. Statistical analysis included descriptive data analysis and paired t test.
  
  
  RESULTS
  Hydroxypropyl-Guar resulted in a decrease in aqueous tear evaporation at 30 minutes postinstillation under 25% to 35% relative humidity (RH) (13.2% reduction, P=0.044) and 35% to 45% RH (10% reduction, P=0.028) conditions. The effect of HP-Guar at 60 minutes postinstillation also decreased aqueous tear evaporation but to a lesser degree. Normal saline solution produced no statistically significant increases and decreases of evaporation.
  
  
  CONCLUSIONS
  Aqueous tear evaporation contributes significantly to aqueous tear loss and is humidity dependent. An HP-guar containing solution decreased aqueous tear evaporation 30 and 60 minutes after application. The use of topical medication with known antievaporative effect may be beneficial in dry eye therapy. This effect may also be achieved in normal eyes or sub-clinical dry eyes when in low RH environments.
authors.affiliation: Department of Ophthalmology, The University of Texas Southwestern Medical Center at Dallas, TX, USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Uchiyama
authors.forename: Mario A
authors.initials: MA
authors.lastname: Di Pascuale
authors.forename: Igor A
authors.initials: IA
authors.lastname: Butovich
authors.forename: James P
authors.initials: JP
authors.lastname: McCulley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005123:Eye / Q000378:metabolism*; D005260:Female; D006801:Humans; D006813:Humidity; D007638:Keratoconjunctivitis Sicca / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions / Q000737:chemistry* / Q000627:therapeutic use*; D011134:Polysaccharides / Q000032:analysis*; D013666:Tears / Q000378:metabolism*; D013997:Time Factors; D014835:Volatilization / Q000187:drug effects
chemical_list: D009883:Ophthalmic Solutions; D011134:Polysaccharides; C519976:hydroxypropyl guar