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Comparison of Three Different Tonometers in Eyes with Angle Closure

Lee, Tae-Eun, MD, PhD1,2; Yoo, Chungkwon, MD, PhD2*; Kim, Yong Yeon, MD, PhD2

doi: 10.1097/OPX.0000000000001325

SIGNIFICANCE Precise measurement of intraocular pressure (IOP) is essential when diagnosing and managing glaucoma. We compared the IOP readings of three different tonometers and analyzed agreement among tonometers in eyes with high IOPs.

PURPOSE The purpose of this study was to compare the IOP readings obtained using a Goldmann applanation tonometer (GAT), a rebound tonometer (RT), and a Tono-Pen (TP) in angle-closure eyes with elevated IOP before and after medical IOP-lowering therapy.

METHODS Twenty-five eyes of 25 patients with angle closure and IOPs of greater than 30 mmHg were enrolled. Intraocular pressure was measured using RT (iCare Pro), TP (Tono-Pen XL), and GAT before and after medical treatment. The mean IOP readings of the tonometers were compared before and after treatment. The agreement among the tonometers was assessed via Bland-Altman analysis.

RESULTS The measurements from 22 eyes of 22 patients were suitable for statistical analyses. Before medical treatment, the mean TP-IOP was significantly lower than the mean GAT-IOP (44.0 ± 10.3 vs. 50.4 ± 8.9 mmHg, respectively; P < .001), but no significant difference was evident between the RT-IOP and the GAT-IOP (50.8 ± 10.9 vs. 50.4 ± 8.9 mmHg, respectively; P = .79). After IOP-lowering treatment, the mean GAT-IOP (14.9 ± 4.7 mmHg) did not differ from either the mean RT-IOP (15.6 ± 4.4 mmHg) or the mean TP-IOP (15.4 ± 5.0 mmHg; P = .05 and P = .18, respectively). The random measurement error among tonometers was greater for high IOP readings.

CONCLUSIONS Compared with RT or GAT, TP underestimated IOP in angle-closure eyes with a GAT-IOP of greater than 30 mmHg. Intraocular pressure reading agreement among the three tonometers was lower in eyes with high IOP.

1Department of Ophthalmology, Chonbuk National University Medical School and Hospital, Jeonju, South Korea

2Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea *

Supplemental Digital Content: Appendix Table A1, available at, details the medical treatment used in each patient, including the intraocular pressure–lowering medications given to each patient.

Submitted: April 22, 2018

Accepted: September 25, 2018

Funding/Support: None of the authors have reported funding/support.

Conflict of Interest Disclosure: None of the authors have reported a financial conflict of interest.

Study Registration Information: IRB no. AS15171.

Author Contributions: Conceptualization: T-EL, CY, YYK; Data Curation: T-EL, CY; Formal Analysis: T-EL, CY; Investigation: T-EL; Methodology: T-EL, CY, YYK; Project Administration: T-EL; Resources: T-EL; Supervision: CY, YYK; Validation: CY, YYK; Writing – Original Draft: T-EL; Writing – Review & Editing: CY, YYK.

Supplemental Digital Content: Direct URL links are provided within the text.

© 2019 American Academy of Optometry