2M.D. Asistant, Kafkas University Faculty of Medicine, Department of Ophthalmology, Kars/TURKEY
3M.D. Professor, Kafkas University Faculty of Medicine, Department of Ophthalmology, Kars/TURKEY Purpose: To compare the intraocular pressure (IOP) readings taken with Tomey FT-1000 non contact tonometer (TNCT) and Canon XT-20 non contact tonometer (CNCT) with the Goldmann applanation tonometer (GAT) and to evaluate the influence of central corneal thickness (CCT) on the IOP measurements.
Materials and Methods: A total of 65 right eyes of 65 subjects without any ocular pathology were included in this prospective and randomised study. All patients underwent ultrasonic CCT measurement, followed by IOP evaluation with the GAT, TNCT and CNCT.
Results: The average CCT was 517.1±31.4 μm. The mean corrected IOP values obtained by GAT, TNCT and CNCT were 16.1±4.5 mmHg, 16.9±4.4 mmHg and 19.7±4.5 mmHg respectively. Both of the non contact tonometers significantly underestimated IOP compare with the GAT measurements. (p<0.001) There was a significantly good correlation between GAT and TNCT (r=0.695, p<0.001), as well as between GAT and CNCT (r=0.759, p<0.001). The Bland-Altman analysis showed a mean difference between TNCT and GAT of 2.4±4.1 mmHg, with 95% limits of agreement determined as -5.5 to +10.4 mmHg, a mean difference between CNCT and GAT of 1.6±3.2 mmHg, with 95% limits of agreement determined as -4.7 to 8.0 mmHg.
Conclusions: Although there is good clinical accordance between non contact tonometers and GAT, both of the non contact tonometers significantly underestimated IOP compare with the GAT. This should always be taken into consideration when it is used clinically.
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