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M.M. Iester, F. Scrimieri, F. De Feo, R. Scotto, C. Traverso, G. Calabria; Tonopen XL: Correlation With Central Cornea Thickness . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4867.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the intraocular pressure (IOP) values obtained with the new Tonopen XL (Mentor) and those with Goldmann tonometer (Haag–Streit) and to evaluate the influence of other ocular parameters on the Tonopen measurements. Methods: The IOP of 90 eyes was assessed by Goldmann tonometer and Tonopen XL tonometer. Three IOP measurements were obtained for both instruments and the mean values were calculated and used for the analysis. For the Tonopen XL after four valid readings the instrument calculated the mean IOP which was shown on the display. The standard deviation of the value obtained was displayed. Only statistical reliability values (5%) were included in the study. TheTonopen was calibrated before each session. For each patient axial length, refractive error, corneal curvature, visual acuity, central corneal thickness (CCT) were assessed. The results were analyzed by descriptive analysis and when the distribution of the data was normal, paired t–test and Pearson’s r coefficient were used to compare and correlated IOP measurements between Tonopen values and the other parameters. When the distribution of the data was non–normal, Wilcoxon matched pair test and Spearman coefficient were used. The agreement between Goldmann and Tonopen values was also calculated. Results: A statistically significant difference (P<0.0001) was found between the IOP readings obtained by Goldmann tonometer (16.71+/–3.18 mmHg (mean +/– standard deviation)) and the Tonopen XL (15.18+/–4.17 mmHg). A significant correlation was found between the Goldmann value and Tonopen XL values (r=0.5, P<0.001). A good agreement was found between Goldmann and Tonopen values. Tonopen XL was significantly correlated to CCT (r=0.28, P=0.0067). No other significant correlation was found. Conclusions: The new Tonopen XL provides clinically similar results than with Goldmann even if a statistical significant difference was found. Tonopen XL is slightly correlated to CCT.
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