title: Modern disposable hydrogel contact lens removal has a minimal effect on intraocular pressure.
abstract: OBJECTIVE
  To determine whether the removal of modern disposable hydrogel contact lenses may influence intraocular pressure (IOP) measurement, and if so, how long the effect may last.
  
  
  METHODS
  Twenty-five healthy experienced contact lens wearers aged 19-25 inserted their lenses at least 30 min prior to the study. Each participant was asked to remove a contact lens from one eye (control eye, selected at random) upon commencement of the study, and then to remove the lens in the other eye (lens-wearing eye) after a 30 min washout period. IOP was measured immediately in both eyes using non-contact tonometry, then repeated every 3 min for 12 min. To determine the change in IOP due to lens removal, the IOP in the lens-wearing eye was compared to the control eye using paired t-tests at each time point.
  
  
  RESULTS
  The IOP was significantly higher in the lens-wearing eye immediately following lens removal (0.7 ± 1.0 mmHg, t(24) = 3.46, p < 0.01), but was within baseline values at 3 min (0.2 ± 1.0 mmHg, t(24) = 0.84, p = 0.41), 6 min (0.3 ± 1.1 mmHg, t(24) = 1.39, p = 0.18), 9 min (0.3 ± 1.2 mmHg, t(24) = 1.14, p = 0.27) and 12 min (-0.1 ± 0.9 mmHg, t(24) = -0.49, p = 0.63, paired t-test).
  
  
  CONCLUSIONS
  There was a slight statistically significant increase in IOP following contact lens removal, with a maximum duration of 3 min. Given the small magnitude of the change in IOP, and its transient nature, there appears to be no clinical reason to delay IOP measurements following the removal of modern disposable hydrogel contact lenses.
authors.affiliation: School of Optometry and Vision Sciences, College of Biomedical & Life Sciences, Cardiff University, Cardiff, UK.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Hamilton-Maxwell
authors.forename: Nicole
authors.initials: N
authors.lastname: King
mesh_terms: D000328:Adult; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D020100:Hydrogels; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D013997:Time Factors; D014065:Tonometry, Ocular / Q000379:methods*; D055815:Young Adult
chemical_list: D020100:Hydrogels
keywords: contact lenses; intraocular pressure; ocular; soft contact lenses; tonometry