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Bryan R. Costin, Gloria P. Fleming, Paul A. Weber, Ashraf M. Mahmoud, Cynthia J. Roberts; Corneal Biomechanical Properties and Intraocular Pressure Measurement in Primary Open Angle Glaucoma versus Normal Control Subjects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5178.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate differences in corneal biomechanical properties, intraocular pressure (IOP) and other parameters between primary open angle glaucoma (POAG) and control subjects.
17 eyes from 14 POAG subjects and 23 eyes of 15 normal subjects underwent corneal topography using the Galilei Dual Scheimpflug Analyzer; intraocular pressure (IOP) using Goldmann applanation tonometry (GAT), Pascal Dynamic Contour Tonometry (DCT), and corneal compensated IOP (IOPcc) using the Reichert Ocular Response Analyzer (ORA); corneal hysteresis (CH) using the ORA; and central corneal thickness (CCT) using two ultrasonic pachymeters. Results from POAG and control eyes were then compared using t-tests.
The POAG group was slightly older than the control group (mean 63.8 ± 10.9 years, mean 56.5 ± 5.8 years, respectively, p = 0.019). CCT was comparable between both groups (546 ± 36 um, 543 ± 35um, p = 0.8). A statistically significant difference was found between GAT vs DCT and IOPcc: Mean GAT IOP was not significantly different between POAG and controls (14 ± 3.6 mm Hg, 13 ± 2.5 mm Hg, p = 0.15), whereas mean DCT IOP did show a significant difference between the two groups (18 ± 2.4 mm Hg, 15 ± 2.2 mm Hg, p = 0.0004), as did mean IOPcc (17.4 ± 2.5 mm Hg, 13.9 ± 2.5 mm Hg, p = 0.0001). The difference between GAT vs DCT (4 mm Hg in POAG, 2 mm Hg in controls, p = 0.0106) and GAT vs ORA (2 mm Hg in POAG, 0.9 mm Hg in controls, p = 0.0134) was of a significantly greater magnitude in POAG subjects when compared to controls. CH was also significantly different in POAG subjects when compared to controls (8.9 ± 1.6, 10.2 ± 1.2, p = 0.0087).
The differences between GAT IOP vs DCT and GAT vs ORA IOP are both greater in patients with POAG when compared to controls, independent of CCT. This is likely due to differences in the corneal biomechanical properties in patients with POAG, which has been shown to have a significant influence on measurement error of GAT IOP. Underestimation of GAT IOP could affect treatment decisions in POAG.
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