title: The effect of hydrogel and silicone hydrogel contact lenses on the measurement of intraocular pressure with rebound tonometry.
abstract: OBJECTIVE
  To assess the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) and silicone hydrogel (senofilcon A) contact lenses (CLs) of different powers.
  
  
  METHODS
  The experimental group comprised 36 subjects (19 male, 17 female). IOP measurements were undertaken on the subject's right eyes in random order using a rebound tonometer (ICare). The CLs had powers of +2.00D, -2.00D and -6.00D. Six measurements were taken over each contact lens and also before and after the CLs had been worn.
  
  
  RESULTS
  A good correlation was found between IOP measurements with and without CLs (all r≥0.80; p<0.05). Bland Altman plots did not show any significant trend in the difference in IOP readings with and without CLs as a function of IOP value. A two-way ANOVA revealed a significant effect of material and power (p<0.01) but no interaction. All the comparisons between the measurements without CLs and with hydrogel CLs were significant (p<0.01). The comparisons with silicone hydrogel CLs were not significant.
  
  
  CONCLUSIONS
  Rebound tonometry can be reliably performed over silicone hydrogel CLs. With hydrogel CLs, the measurements were lower than those without CLs. However, despite the fact that these differences were statistically significant, their clinical significance was minimal.
authors.affiliation: Degree Course in Optics and Optometry, Faculty of Mathematics, Physics and Natural Sciences, Roma TRE University, Via Galvani, 6 00153 Rome, Italy. zeri@fis.uniroma3.it
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Zeri
authors.forename: Paolo
authors.initials: P
authors.lastname: Calcatelli
authors.forename: Bernardo
authors.initials: B
authors.lastname: Donini
authors.forename: Luigi
authors.initials: L
authors.lastname: Lupelli
authors.forename: Luciana
authors.initials: L
authors.lastname: Zarrilli
authors.forename: Peter G
authors.initials: PG
authors.lastname: Swann
mesh_terms: D000293:Adolescent; D000328:Adult; D016477:Artifacts; D001363:Awards and Prizes; D003263:Contact Lenses, Hydrophilic; D005260:Female; D006801:Humans; D020100:Hydrogels; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012825:Silicon; D014065:Tonometry, Ocular / Q000379:methods*; D055815:Young Adult
chemical_list: D020100:Hydrogels; D012825:Silicon