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M. Shimmyo, P. N. Orloff, N. I. Hayashi; Corneal Hysteresis, Corneal Resistance Factor and Intraocular Pressure of Normal, High Tension and Normal Tension Glaucoma Eyes. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2047. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The Goldmann applanation tonometry (GAT) is affected by biomechanical properties of the cornea. Intraocular pressure (IOP) was measured with GAT and the Reichert's Ocular Response Analyzer (ORA) to determine if the corneal properties of normal tension glaucoma (NTG) eyes are different from normal or high tension glaucoma (HTG) eyes, secondly to see if ORA provides meaningful alternate information in determining true IOP.
Cross-sectional observational review of IOP and ORA parameters of randomly selected one eye of 357 normal, 155 HTG and 102 NTG patients.
The mean IOP compensated for corneal effects (IOPcc) was similar to GAT in normal and HTG eyes. In NTG, the mean IOPcc of 19.8 ± 3.41 mmHg was much higher than the mean GAT of 14.4 ± 3.37 mmHg. NTG eyes have a significantly thinner central corneal thickness (CCT) of 513 ± 39 µm, a lower corneal hysteresis (CH) of 5.96 ± 1.09 mmHg, and a lower corneal resistance factor (CRF) of 6.31 ± 1.14 mmHg when compared to the means of normal CCT of 541 ± 33 µm normal CH of 10.60 ± 1.54 mmHg normal CRF of 10.15 ± 1.60 mmHg (p<0.001). It is notable that 38% of NTG eyes have an IOPcc above 21 mmHg, 72% of them have an IOPcc above 18 mmHg.
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