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Test–retest variability of intraocular pressure and ocular pulse amplitude for dynamic contour tonometry: a multicentre study
  1. P Fogagnolo1,
  2. M Figus2,
  3. P Frezzotti3,
  4. M Iester4,
  5. F Oddone1,
  6. M Zeppieri5,
  7. A Ferreras6,
  8. P Brusini5,
  9. L Rossetti7,
  10. N Orzalesi7
  1. 1GB Bietti Foundation—IRCCS, Rome, Italy
  2. 2Eye Clinic, Department of Neuroscience, University of Pisa, Pisa, Italy
  3. 3Dipartimento di Scienze oftalmologiche e Neurochirurgiche, Universita' degli Studi di Siena, Siena, Italy
  4. 4Clinica Oculistica, Università di Genova, Genoa, Italy
  5. 5Azienda Ospedaliero-Universitaria, S Maria della Misericordia di Udine, SOC di Oculistica, Udine, Italy
  6. 6Department of Ophthalmology, Miguel Servet University Hospital, University of Zaragoza, Zaragoza, Spain
  7. 7Eye Clinic, Department of Medicine, Surgery and Dentistry, San Paolo Hospital, University of Milan, Milan, Italy
  1. Correspondence to Dr Paolo Fogagnolo, Eye Clinic, San Paolo Hospital, Via di Rudini' 8, 20142 Milan, Italy; fogagnolopaolo{at}


Aims To assess the test–retest variability of intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements utilising dynamic contour tonometry (DCT) and to evaluate possible influential factors.

Methods The study included 350 consecutive subjects (175 glaucoma, 175 control; one eye per subject) from seven European centres. IOP was measured once with a Goldmann applanation tonometer (GAT) and twice by DCT (DCT1, DCT2) in a randomised sequence. OPA was also recorded for both DCT measurements. Differences (DCT1-DCT2; OPA1-OPA2; GAT-DCT1; GAT-DCT2) were assessed using the t test. The intraclass coefficient of correlation (ICC) and coefficient of variation (CoV) for DCT and OPA were calculated.

Results DCT1 was 0.6±1.6 mm Hg higher than DCT2 (p<0.001); OPA1 was 0.1±0.7 mm Hg higher than OPA2 (p=0.02). Results were not influenced by randomisation test order. In both glaucoma and normal subjects, DCT and OPA showed ICC>0.90 and >0.76, and CoV=4.8–5.0% and 10.3–10.5%, respectively. DCT1 and 2 were 2.4±2.6 and 1.8±2.6 mm Hg higher respectively than GAT (p<0.001).

Discussion DCT test–retest variability was almost perfect for IOP and good for OPA. Tonometry measurements with DCT tended to be overestimated compared with GAT.

  • Tonometry
  • intraocular pressure (IOP)
  • reproducibility
  • primary open-angle glaucoma (POAG)
  • ocular pulse amplitude

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  • Preliminary results presented at ARVO, Fort Lauderdale, USA, 3–7 May 2009.

  • Competing interests None.

  • Patient consent Obtained.

  • Provenance and peer review Not commissioned; externally peer reviewed.