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Lee, Seong, Kang, Cho, and Lee: Comparison of Rebound Tonometer, Non-Contact Tonometer, Goldmann Applanation Tonometer and the Relationship to Central Corneal Thickness
Original Article
Journal of the Korean Ophthalmological Society

Journal of the Korean Ophthalmological Society 2012; 53(7): 988-995.

Published online: 13 July 2012

DOI: https://doi.org/10.3341/jkos.2012.53.7.988

Comparison of Rebound Tonometer, Non-Contact Tonometer, Goldmann Applanation Tonometer and the Relationship to Central Corneal Thickness

Juhyang Lee, MD, Mincheol Seong, MD, Minho Kang, MD, Heeyoon Cho, MD, Yoonjung Lee, MD

Department of Ophthalmology, Hanyang University Guri Hospital, Hanyang University College of Medicine, Guri, Korea.

Address reprint requests to Mincheol Seong, MD. Department of Ophthalmology, Hanyang University Guri Hospital, #153 Gyeongchun-ro, Guri 471-701, Korea. Tel: 82-31-560-2350, Fax: 82-31-564-9479, goddns76@hanmail.net

Received 25 July 2011       Accepted 21 May 2012

Copyright © 2012 The Korean Ophthalmological Society

Abstract

Purpose

To compare the level of accuracy of intraocular pressure (IOP) measurements of a rebound tonometer (RT) Icare®, and non-contact tonometer (NCT), using Goldmann Applanation tonometer (GAT) as a reference to evaluate the influence of central corneal thickness (CCT) on IOP readings in the Korean population.

Methods

In a prospective study of 273 eyes, IOP was measured with RT, GAT, and NCT and compared to CCT measurements. Patients were assigned to one of 3 groups based on IOP measurements of GAT and 1 of 2 groups based on CCT. The comparison of the IOP values of RT, GAT, and NCT was performed between the IOP and CCT groups, and the differences among tonometers were evaluated.

Results

The RT showed statistically significant correlation with the GAT compared to the NCT. The CCT was related to RT measurements. The RT values compared to the GAT was underestimated in thin corneas and overestimated in thick corneas.

Conclusions

There was a significant correlation between the RT and the GAT measurements compared with the NCT. However, RT is influenced by CCT and correlates less with GAT in low IOP ranges, suggesting that corneal thickness should be taken into consideration during such measurements.

Keywords: Central corneal thickness, Goldmann applanation tonometer, Non-contact tonometer, Rebound tonometer

Figures and Tables

Figure 1
The correlation between Goldmann applanation tonometer and rebound tonometer IOP measurements (r = 0.913, p < 0.001).
jkos-53-988-g001
Figure 2
Bland-Altman plots of agreement between Goldmann applanation tonometer and rebound tonometer for each eye measured (A), and Goldmann applanation tonometer and Non-contact tonometer (B). The differences in IOP of both tonometers (Goldmann applanation tonometer value minus rebound tonometer value (or non-contact tonometer value), mmHg) is plotted against the average of the IOP of both tonometers. The solid line is the mean of the average IOP values of both tonometers. The dotted horizontal lines are ±1.96 SD confidence interval (CI) (i.e. 95% of the points should fall within these lines).
jkos-53-988-g002
Figure 3
Frequency distribution of differences between rebound tonometer, Goldmann applanation tonometer, and noncontact tonometer measurements.
jkos-53-988-g003
Figure 4
Scatterplots showing the relationship between central corneal thickness and IOP value of Goldmann applanation tonometer (R2 = 0.057, p < 0.001) (A), IOP values of rebound tonometer (R2 = 0.104, p < 0.001) (B).
jkos-53-988-g004
Table 1
Summary of the subject characteristics, IOP measurements (mm Hg) using the 3 tonometers, and corneal thickness
jkos-53-988-i001

Data are expressed as mean ± SD or number.

IOP = intraocular pressure; IOPNCT = IOP measurement of a noncontact tonometer; IOPRT = IOP measurement of a Icare rebound tonometer; IOPGAT = IOP measurement of a Goldmann applanation tonometer; CCT = central corneal thickness.

Table 2
Bland-Altman analysis of IOP measurements using different tonometers (mean difference ± SD and 95% LoAs)
jkos-53-988-i002

IOP = intraocular pressure; IOPNCT = IOP measurement of a noncontact tonometer; IOPRT = IOP measurement of a Icare rebound tonometer; IOPGAT = IOP measurement of a Goldmann applanation tonometer; CCT = central corneal thickness; SD = standard deviation; LoA = limits of agreement; Lower LoA = mean - 1.96 × SD; Upper LoA = mean + 1.96 × SD; Width of LoA = upper LoA-lower LoA.

Table 3
Comparison of the IOP measurements of Icare® rebound tonometer, Goldmann applanation tonometer, and noncontact tonometer and the mean differences of each tonometers between low IOP, medium IOP, and high IOP by GAT
jkos-53-988-i003

IOP = intraocular pressure; GAT = Goldmann applanation tonometer; IOPNCT = IOP measurement of a noncontact tonometer; IOPRT = IOP measurement of a Icare rebound tonometer; IOPGAT = IOP measurement of a Goldmann applanation tonometer; CCT = central corneal thickness.

*Mean difference of IOPs measured by two tonometers; †Correlation of IOP by Goldmann applanation tonometer and IOP by rebound tonometer (pearson correlation analysis).

Table 4
Comparison of the IOP measurements of Icare® rebound tonometer, Goldmann applanation tonometer, and noncontact tonometer and the mean differences of each tonometers between thinner CCT group and thicker CCT group
jkos-53-988-i004

Values are presented as mean ± SD.

IOP = intraocular pressure; GAT = goldmann applanation tonometer; NCT = noncontact tonometer; CCT = central corneal thickness; IOPGAT = IOP measurement of a Goldmann applanation tonometer; IOPRT = IOP measurement of a Icare rebound tonometer; IOPNCT = IOP measurement of a noncontact tonometer.

*Statistical significance was tested by independent paired t-test; †Correlation between the IOP measurements of two tonometers by pearson correlation analysis.

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