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M. Mueller–Holz, E. Schmidt, A.G. Boehm, L.E. Pillunat; Comparison of IOP–Measurements Obtained by the Non–Contact Tonometer AT555TM and Goldmann Applanation Tonometry . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4847.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: IOP is the main treatable risk factor for glaucomatous cupping of the optic nerve head. Therefore, determination of IOP with contact or non–contact tonometer is an indispensable tool for monitoring glaucoma patients and ocular hypertensives in clinical routine. Aim of the study was to compare the results of IOP measurements obtained by the Reichert non–contact tonometer AT 555TM and Goldmann applanation tonometry as the gold standard. Methods: 41 patients (17 male, 24 female, mean age 69 years) without pathological corneal findings were included. IOP measurements were performed with a calibrated slit lamp mounted Goldmann Applanation tonometer (APT) and the Reichert pulse air non–contact tonometer AT 555TM (NCT) in a randomly sequence at one randomly chosen eye. The measurements were repeated three times with both methods and the means were calculated. In addition corneal astigmatism (CA), ocular axial length (OAL) and central corneal thickness (CCT) were determined. For statistics Pearsons linear correlation and Bland–Altmann–Analysis (BAA) were used.Results: The correlation coefficient between the mean IOP results of APT and NCT was 0,77 (p ≤ 0,0001). BAA showed that IOP measurements by NCT are higher than those by APT (mean: +2,9 mmHg). The IOP measured by NCT and APT were 17,0 ± 3,9 mmHg (mean±SD; range: 11–27 mmHg) and 14,1±3,5 mmHg (range: 9–20 mmHg), respectively. Mean CA, OAL and CCT were 0,84±0,75 D, 23,68±1,99 mm and 552±49µm. There was no significant correlation between results of NCT or APT and CA, OAL, CCT or age. Conclusions: The non–contact tonometer tested in this study group showed an offset of +20 percent compared with Goldmann tonometry. This may be tolerable for screening IOP measurements but not for glaucoma monitoring. A calibration of the used NCT and a second study was initiated.
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