title: Day-to-day variability in intraocular pressure in glaucoma and ocular hypertension.
abstract: OBJECTIVE
  To investigate the day-to-day repeatability of intraocular pressure (IOP) measurements.
  
  
  METHODS
  A prospective cohort study of untreated patients presenting with primary open-angle glaucoma or ocular hypertension presenting with IOP>21 mm Hg. IOP was measured by masked Goldmann tonometry at 08:00, 11:00 and 16:00 at each of the three weekly visits. After starting travaprost (0.004%) to both eyes, the measurements were repeated for a further three weekly visits. Day-to-day repeatability was estimated before and after commencing medication and reported as the coefficient of repeatability and coefficient of variability.
  
  
  RESULTS
  At the 8:00 time point, mean IOPs were 26.1 and 17.9 mm Hg in the eye with higher pressure before and after starting treatment, respectively. Coefficient of repeatability and coefficient of variability were 6.8 mm Hg and 10.0%, respectively, before treatment, and 4.6 mm Hg and 10.5% on treatment. Therefore, before treatment and after starting medication the IOP lay within a range of ±20% of the mean IOP with 95% confidence.
  
  
  CONCLUSIONS
  The non-therapeutic variability from day to day significantly undermines the precision of IOP estimation and of the estimation of medication effectiveness even when the time of day is standardised in patients with primary open-angle glaucoma/ocular hypertension.
authors.affiliation: Tennent Institute of Ophthalmology, Gartnavel Hospital, Great Western Road, Glasgow G12 0YN, UK. rotchford@doctors.org.uk
authors.forename: Alan P
authors.initials: AP
authors.lastname: Rotchford
authors.forename: Samreen
authors.initials: S
authors.lastname: Uppal
authors.forename: Arun
authors.initials: A
authors.lastname: Lakshmanan
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: King
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use; D002940:Circadian Rhythm; D003008:Cloprostenol / Q000031:analogs & derivatives / Q000627:therapeutic use; D015331:Cohort Studies; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000188:drug therapy; D006068:Gonioscopy; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000188:drug therapy; D011446:Prospective Studies; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000592:standards*; D000069557:Travoprost; D014794:Visual Fields
chemical_list: D000959:Antihypertensive Agents; D003008:Cloprostenol; D000069557:Travoprost