title: [Diurnal variability of intraocular pressure].
abstract: OBJECTIVE
  To assess whether there are variations in the intraocular pressure (IOP) between the morning and afternoon in healthy subjects.
  
  
  METHODS
  This study was carried out in a Primary Care Health Center among usual patients of general practitioners. Two measurements of the intraocular pressure were assessed on the same day (between 8 and 9 a.m. and between 5 and 6 p.m.) using a Perkins applanation tonometer. The subjects (119 females and 101 males) had a mean age of 46.3 years, with ages ranging between 14 and 83 years. They were proportionally distributed among 4 age groups (14-24, 25-44, 45-64 and >65 years).
  
  
  RESULTS
  The IOP mean values were: right eye, morning time and afternoon, 13.29 and 11.81 mm Hg, respectively (p<0.001); left eye, morning time and afternoon, 13.48 and 12.04 mm Hg (p<0.001). The IOP was significantly higher in males than in females, and showed a weak association with age.
  
  
  CONCLUSIONS
  We found a diurnal variation of IOP of approximately 1.5 mm Hg. The time of day when the IOP is measured needs to be considered as a variable in research in ocular hypertension and glaucoma.
authors.affiliation: Centro de Salud Docente Santa M.a de Benquerencia, Toledo, Spain. ijd02@hotmail.com
authors.forename: J I
authors.initials: JI
authors.lastname: Jaén-Díaz
authors.forename: B
authors.initials: B
authors.lastname: Cordero-García
authors.forename: F
authors.initials: F
authors.lastname: López-de-Castro
authors.forename: C
authors.initials: C
authors.lastname: de-Castro-Mesa
authors.forename: F
authors.initials: F
authors.lastname: Castilla-López-Madridejos
authors.forename: F
authors.initials: F
authors.lastname: Berciano-Martínez
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D035843:Biomedical Research; D002940:Circadian Rhythm; D003627:Data Interpretation, Statistical; D005194:Family Practice; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008365:Manometry; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis; D011320:Primary Health Care; D012737:Sex Factors; D013997:Time Factors