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Test-retest variability of intraocular pressure and ocular pulse amplitude for Dynamic Contour Tonometry: a multicenter study
  1. Paolo Fogagnolo1,*,
  2. Michele Figus2,
  3. Paolo Frezzotti3,
  4. Michele Iester4,
  5. Francesco Oddone1,
  6. Mark Zeppieri5,
  7. Antonio Ferreras6,
  8. Paolo Brusini5,
  9. Luca Rossetti7,
  10. Nicola Orzalesi7
  1. 1 GB Bietti Foundation, IRCSS, Roma, Italy;
  2. 2 Eye Clinic, Department of Neuroscience, University of Pisa, Pisa, Italy;
  3. 3 Dipartimento di Scienze oftalmologiche e Neurochirurgiche, Universita' degli Studi di Siena, Siena, Italy;
  4. 4 Clinica Oculistica, University di Genova, Genova, Italy;
  5. 5 Azienda Ospedaliero-Universitaria, S. Maria della Misericordia di Udine, S.O.C di Oculistica, Udine, Italy;
  6. 6 Department of Ophthalmology, Miguel Servet University Hospital, University of Zaragoza, Zaragoza, Italy;
  7. 7 Eye Clinic, University of Milan, Spain
  1. Correspondence to: Paolo Fogagnolo, GB Bietti Foundation for the Study and Research in Ophthalmology, IRCSS, Rome, via Pordenone, 11, Canegrate, 20010, Italy; fogagnolopaolo{at}


Aims: To assess the test-retest variability of intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements utilizing 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 7 European centers. IOP was measured once by Goldmann applanation tonometer (GAT) and twice by DCT (DCT1, DCT2) in a randomized sequence. OPA was also recorded for both DCT measurements. Differences (DCT1-DCT2; OPA1-OPA2; GAT-DCT1; GAT-DCT2) were assessed using the t-test. Intraclass coefficient of correlation (ICC) and coefficient of variation (CoV) for DCT and OPA were calculated.

Results: DCT1 was 0.6±1.6 mmHg higher than DCT2 (P<0.001); OPA1 was 0.1±0.7 mmHg higher than OPA2 (P=0.02). Results were not influenced by randomization 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 respectively 2.4±2.6 and 1.8±2.6 mmHg higher 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 to GAT.

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