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C. B. Toris, R. P. Basham, T. V. Johnson, III, S. Fan, E. C. Pike, C. B. Camras; The Effect of Ocular Physical Properties on Intraocular Pressure Measurements With Six Different Tonometers. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2097.
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© ARVO (1962-2015); The Authors (2016-present)
This clinical study evaluates the effects of central cornea thickness (CCT), corneal curvature, axial length, scleral rigidity and anterior chamber depth on the measurement of intraocular pressure (IOP) with six tonometers. We hypothesize that tonometers demonstrating independence from ocular physical properties, especially CCT, may improve the accuracy of IOP estimation.
A total of 118 eyes from 59 subjects (23 to 70 years of age) were included in the analysis. Measurements included CCT, axial length and anterior chamber depth by ultrasound; corneal curvature by keratometry and partial coherence interferometry; and scleral rigidity by Schiotz tonometry. IOP was measured with a Goldmann applanation tonometer, Tono-Pen, Langham ocular blood flow pneumatonometer, Reichart pneumatonometer, Pascal Dynamic Contour tonometer and Schiotz tonometer. Each volunteer underwent all measurements during a one hour study visit.
Positive correlations between CCT and IOP measurement were found for the Schiotz tonometer (P < 0.01, R-square = 0.136), the Reichart pneumatonometer (P < 0.01, R-square = 0.058), the Tono-Pen (P < 0.01, R-square = 0.090), the Goldmann applanation tonometer (P = 0.05, R-square = 0.032), and the Langham ocular blood flow pneumatonometer (P = 0.06, R-square = 0.029). No correlation was found between CCT and IOP measurement with the Pascal Dynamic Contour tonometer (P = 0.70, R-square = 0.001). Furthermore, no statistically significant correlations were observed between IOP measurements with any of the tonometers and anterior chamber depth or corneal curvature.
The use of the Pascal Dynamic Contour tonometer may improve the accuracy of tonometry in a large clinic setting where inter-patient variability of CCT can be expected to be significant.
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