title: The difference in intraocular pressure readings between 3 applanation tonometers is independent of central corneal thickness, in glaucomatous and nonglaucomatous eyes.
abstract: OBJECTIVE
  To look at tonometry differences between 3 tonometers and to correlate this difference with central corneal thickness (CCT) in glaucomatous and nonglaucomatous eyes.
  
  
  METHODS
  A total of 145 patients were recruited (39 with glaucoma). Intraocular pressure (IOP) was carried out using the Tonosafe (TS), Tono-Pen XL (TP), and Goldmann applanation tonometer (GAT). CCT was also performed using a digital pachymeter.
  
  
  RESULTS
  The TS underestimated IOP when compared with the GAT by a mean (±SD) of 1.03±2.14 mm Hg (P<0.001). The TP when compared to the GAT overestimated IOP by a mean (±SD) of +1.09±6.38 mm Hg (P=0.071). We found only 31% of TP readings to be within ±2 mm Hg of the GAT readings and only 60% to be within ±4 mm Hg of the GAT readings. Correlation was poor (F=0.247) between the GAT and TP with the coefficient of determination being 0.061. The difference in IOP was independent of CCT and a diagnosis of glaucoma.
  
  
  CONCLUSIONS
  The TS, when compared with the GAT, underestimates IOP with a tendency for this to increase in the higher range of IOP readings. The TP is poorly correlated with the GAT.
authors: *Department of Ophthalmology, Mid-Western Regional Hospital, Dooradoyle, Limerick †Department of Ophthalmology, Cork University Hospital, Cork, Ireland.
authors: Caroline
authors: C
authors: Baily
authors: Ian
authors: I
authors: Dooley
authors: Niamh
authors: N
authors: Collins
authors: Marie
authors: M
authors: Hickey-Dwyer
mesh_terms: D000328:Adult; D000368:Aged; D003315:Cornea / Q000033:anatomy & histology*; D063171:Corneal Pachymetry; D005260:Female; D005901:Glaucoma / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D014065:Tonometry, Ocular / Q000295:instrumentation*