title: Are disposable prisms an adequate alternative to standard Goldmann tonometry prisms in glaucoma patients?
abstract: OBJECTIVE
  To evaluate the accuracy and reliability of 2 single-use tonometry devices (Tonosafe and Tonojet) as an alternative to standard Goldmann prisms in patients attending dedicated glaucoma clinics.
  
  
  METHODS
  Prospective experimental study with human subjects.
  
  
  METHODS
  Two hundred forty glaucoma patients who attended 2 glaucoma clinics at the Stepping Hill Hospital between January and February 2005.
  
  
  METHODS
  During each examination, intraocular pressure (IOP) was measured 3 times, using the standard Goldmann prism, Tonosafe, and Tonojet, respectively. The prism sequence was predetermined at random using a computer, and the measurements were taken at 5-minute intervals. Data were analyzed using the Bland-Altman method of differences.
  
  
  METHODS
  Intraocular pressure.
  
  
  RESULTS
  Intraocular pressure ranged from 6 to 68 mmHg. Linear regression analysis indicated that there was a proportional bias between Goldmann and Tonosafe (r2 = 0.368, P<.001), especially for values higher than 25 mmHg. On the other hand, there was no statistically significant proportional bias between Goldmann and Tonojet (r2 = 0.006, P = 0.14).
  
  
  CONCLUSIONS
  Caution should be exercised when using Tonosafe prisms in the presence of IOP higher than 25 mmHg. On the other hand, Tonojet is an adequate and useful alternative to the Goldman tonometer for glaucoma patients.
authors.affiliation: Royal Eye Hospital, Manchester, United Kingdom. a.maino@doctors.net.uk
authors.forename: Anna P
authors.initials: AP
authors.lastname: Maino
authors.forename: Laurence H
authors.initials: LH
authors.lastname: Morgan
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hercules
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Tullo
mesh_terms: D004209:Disposable Equipment; D005260:Female; D015812:Glaucoma, Angle-Closure / Q000175:diagnosis*; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis; D011446:Prospective Studies; D015203:Reproducibility of Results; D014065:Tonometry, Ocular / Q000295:instrumentation* / Q000592:standards*