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C.H. Karabatsas, K. Kotsimpou, D.Z. Chatzoulis; Intraocular Pressure Measurements with Applanation Tonometry and with Digital Tonometry Through the Eyelids: Comparative Results . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2182.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare intraocular pressure (IOP) measurements with the Goldman applanation tonometer and the digital portable tonometer TGDc-01 (Raysan Enterprise, Russia) which measures IOP through the eyelids. Methods: IOP measurements were taken in a total of 100 eyes ( 40 normals, 40 eyes with glaucoma, 20 eyes with corneal disease) by two independent observers in a double blind fashion. Analysis was performed by paired t-test, Pearson's correlation and by the Bland & Altman (1986) method for measurements agreement comparison. Results: In the normal eyes group (IOP<20 mm Hg, no corneal disease), both examiners showed no statistically significant differences in IOP measurements with the two instruments (p=0.55, 0.32 for examiners 1 and 2 respectively), with best agreement around the 15 to 17 mm Hg range. For the glaucomatous eyes (IOP > 21 mm Hg), despite the lack of significant mean +/- SD difference between instruments (p=0.17, 0.57 for the two examiners), a trend for the TGD tonometer to measure lower IOP than the Goldman was observed. In the corneal disease group of eyes, significant inter-instrument difference in IOP measurements for one of the two examiners was seen (p=0.05, r=0.85). Inter-observer variability was also assessed for the two tonometers with superior performance of the Goldman tonometer (r=0.63 vs 0.95, interobserver coefficient of reliability [COR = 2 x SD] 9.38 mm Hg vs 4.28 mm Hg). Conclusions: The portable digital tonometer TGDc-01 offers some advantages in terms of conveniency in IOP measurements in some cases. It is useful as a screening tool for eyes with normal IOP and eyes with corneal abnormalities were applanation tonometry is not accurate. However, for eyes with IOP > 21 mm Hg it showed a poor performance compared to applanation tonometry with underestimation of IOP. For the glaucomatous eyes the use of a correction coefficient incorporated in the instruments software may be useful.
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