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M.F. Mueller–Holz, J. Spanier, E. Schmidt, A.G. Boehm, L.E. Pillunat; Dynamic Contour Tonometry vs. Applanation Tonometry – Comparison of IOP–Measurements . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4436.
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© ARVO (1962-2015); The Authors (2016-present)
Goldmann applanation tonometry (GAT) is influenced by corneal characteristics. The dynamic contour tonometer (DCT) was developed to take IOP measurements without corneal limitations. Aim of the study was to compare the results of IOP measurements obtained by DCT and GAT.
67 patients (26 male, 41 female, mean age 53,5 years) without pathological corneal findings were included. IOP measurements were performed with a calibrated slit lamp mounted Goldmann Applanation tonometer and the dynamic contour tonometer (Pascal® Tonometer, Swiss Microtechnology AG Port, Switzerland) in a randomly sequence at one randomly chosen eye. The measurements were repeated three times with both methods and the means were calculated. In addition corneal astigmatism (CA), ocular axial length (OAL) and central corneal thickness (CCT) were determined. For statistics Pearsons linear correlation and Bland–Altmann–Analysis (BAA) were used.
The correlation coefficient between the mean IOP results of GAT and DCT was 0,59 (p ≤ 0,01). BAA showed higher IOP measurements by DCT than by APT (mean±SD: 2,6±3,5 mmHg). The IOP measured by DCT and GAT were 17,1±4,1 mmHg (mean±SD; range: 7–28 mmHg) and 14,5±3,5 mmHg (range: 4–23 mmHg), respectively. Mean CA, OAL and CCT were 1,1±1,4 D; 23,9±1,8 mm and 558±43µm. There was no significant correlation between the results of DCT or GAT and CA, OAL, CCT or age.
The dynamic contour tonometer tested in this study group showed a mean offset of +18 percent compared with Goldmann tonometry. There was no systematic tendency to over– or underestimate higher or lower IOP values. The standard variation of the IOP differences (3,5mmHg) seems to be too high to make both methods replaceable. DCT results seem not to be influenced by CCT. With regard to the offset a re–calibration of the tested DCT should be performed.
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