title: Ocular physiology and artificial tears.
abstract: BACKGROUND
  In this study, we evaluated the pH value of nine artificial tears solutions in order to investigate whether their pH changed over time. These solutions are designed to have a pH value within the ocular comfort range and to come close to the physiological tears' pH.
  
  
  METHODS
  Fifteen bottles of each solution were randomly chosen from different production lots. Increments of 0.05 ml were taken daily from each bottle and measured daily, using a micropH 2002 Crison pH-meter over a period of 60 days.
  
  
  RESULTS
  The values obtained fall within the ocular comfort range. Also, we obtained nonstatistically significant variations over time for each solution (p > 0.01). The results revealed differences between solutions, some solutions coming close to the tear's pH and others being slightly more acidic or alkaline.
  
  
  CONCLUSIONS
  We may assume that all the solutions evaluated will not affect either the ocular physiology or the contact lens wear. The practitioners should know the properties of the solutions, thus selecting the adequate solution for each type of patient.
authors.affiliation: Departament d'Optica, Facultat de Física, Universitat de València, Spain.
authors.forename: A
authors.initials: A
authors.lastname: López-Alemany
authors.forename: R
authors.initials: R
authors.lastname: Montés-Micó
authors.forename: M
authors.initials: M
authors.lastname: García-Valldecabres
mesh_terms: D005500:Follow-Up Studies; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009799:Ocular Physiological Phenomena / Q000187:drug effects; D009883:Ophthalmic Solutions / Q000494:pharmacology*
chemical_list: D009883:Ophthalmic Solutions