Original Research

A comparison of intraocular pressure values obtained with the Tono-Pachymeter NT530P, iCare® rebound tonometer and Goldmann applanation tonometer

N. Rampersad, K. P. Mashige, S. Jhetam
African Vision and Eye Health | South African Optometrist: Vol 70, No 3 | a109 | DOI: https://doi.org/10.4102/aveh.v70i3.109 | © 2011 N. Rampersad, K. P. Mashige, S. Jhetam | This work is licensed under CC Attribution 4.0
Submitted: 11 December 2011 | Published: 11 December 2011

About the author(s)

N. Rampersad, BOptom (UKZN) MEd (UKZN), South Africa
K. P. Mashige, BSc (Wits) BOptom (UDW) CAS (NECO) MOptom (UKZN)
S. Jhetam, BSc (Wits) BOptom (UDW) CAS (NECO) MOptom (UKZN)

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The purpose of this study was to compare the intraocular pressure (IOP) values measured with the Tono-Pachymeter NT530P (Tonopachy™) and the iCare® rebound tonometer (iCare®) with those obtained by the Goldmann applanation tonometer (GAT). The right eyes of 105 subjects aged 18 to 82 years (mean age = 29.27 ± 14.67 years) were assessed with the three tonometers. Central corneal thickness (CCT) was measured first using the Tonopachy™ and then IOP was measured by Tonopachy™, iCare® and GAT. The data was analyzed with descriptive statistics, paired  t-test, correlation and regression analysis. The Bland-Altman method of analysis was used to evaluate agreements between the sets of data from the three devices. The CCT values ranged from 440 µm to 606 µm (mean= 518.49 ± 33.01 µm). There was little or no correlation between CCT and IOP for any of the instruments used in this study (r = 0.29 for Tonopachy™, r = 0.22 for iCare®, r = 0.17 for GAT). The mean IOP measured with the Tonopachy™ was 14.31 ± 3.57 mmHg (range 8.7 mmHg to 31 mmHg) and 16.64 ± 4.38 mmHg (range 8 mmHg to 32 mmHg) using the iCare®. The mean IOP measured with the GAT was 14.79 ± 3.09 mmHg (range 8.7
mmHg to 29.7 mmHg). Using the Bland-Altman method, the upper and lower limits of agreement between the Tonopachy™ and GAT, iCare® and GAT, iCare® and Tonopachy™ were 5.1 mmHg
and –4.2 mmHg, 8.6 mmHg and –4.9 mmHg, 7.5 mmHg and –2.8 mmHg respectively. In 79.1% of the eyes studied, the mean IOP difference between Tonopachy™ and GAT was less than 3 mmHg and in 20.9% of the eyes, the difference was greater than 3 mmHg. However, mean IOP differences of greater than 3 mmHg were obtained by iCare® in comparison with GAT (40%) and Tonopachy™ (34.3%) respectively. Findings of this study suggest that the Tonopachy™ yielded IOP readings that were consistent with those of GAT values while iCare® yielded higher IOP values compared to both GAT and Tonopachy™. (S Afr Optom 2011
70(3) 109-116)


Tono-Pachymeter NT530P; iCare® rebound tonometer; Goldmann applanation tonometer; intraocular pressure; central corneal thickness


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