Original Research

Effects of postural changes on measured intraocular pressure and repeatability of PT-100 tonometer and agreement with applanation and indentation tonometry

Ahmed I. Tairi, Kelechi C. Ogbuehi, Hamayun Zafar, Matthew D. King, Chukwuemeka J. Obinwanne, Khathutshelo P. Mashige, Uchechukwu L. Osuagwu
African Vision and Eye Health | Vol 81, No 1 | a691 | DOI: https://doi.org/10.4102/aveh.v81i1.691 | © 2022 Ahmed I. Tairi, Kelechi C. Ogbuehi, Hamayun Zafar, Matthew D. King, Chukwuemeka J. Obinwanne, Khathutshelo P. Mashige, Uchechukwu L. Osuagwu | This work is licensed under CC Attribution 4.0
Submitted: 14 July 2021 | Published: 24 March 2022

About the author(s)

Ahmed I. Tairi, Department of Optometry and Vision Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
Kelechi C. Ogbuehi, Department of Ophthalmology, Faculty of Medicine, University of Otago, Dunedin, New Zealand
Hamayun Zafar, Department of Rehabilitation Sciences and Rehabilitation Research Chair, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia; and, Department of Odontology, Clinical Oral Physiology, Umea University, Umea, Sweden
Matthew D. King, Department of Architecture, Building and Engineering, Otago Polytechnic, Dunedin, New Zealand
Chukwuemeka J. Obinwanne, Cornea and Contact Lens Department, De Lens Ophthalmics, Family Eye and Vision Care Center, Abuja, Nigeria
Khathutshelo P. Mashige, African Vision Research Institute, Discipline of Optometry, University of KwaZulu-Natal, Durban, South Africa
Uchechukwu L. Osuagwu, African Vision Research Institute, Discipline of Optometry, University of KwaZulu-Natal, Durban, South Africa; and, Translational Health Research Institute (THRI), School of Medicine, Western Sydney University, Campbelltown, Australia


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Abstract

Background: Repeatability and validity are important components of precision in any measurement system.

Aim: This study aimed to determine the effect of change in head and neck position and body posture on the repeatability of intraocular pressure (IOP) measurements with PT-100 non-contact tonometer and compare with Goldmann, PT-100 and Schiøtz tonometer readings.

Setting: Optometry clinic, Saudi Arabia.

Methods: The IOP was measured in one selected eye of 84 healthy participants (mean aged 21.9 ± 2.0 years) using PT-100 in three head and body positions, Goldmann tonometer and Schiøtz on two separate visits, in a randomised fashion. Central corneal thickness (CCT) was measured using an ultrasound pachymeter. The repeatability, agreement and correlations between CCT and IOP differentials were assessed.

Results: The IOP measured in three head and body positions with the PT-100 were similar and comparable to Goldmann IOPs in sessions one and two with 74% and 86% of PT-100 measurements within ±3 mmHg of the Goldmann tonometry, respectively, for sessions one and two. The Schiøtz tonometer-measured IOP was higher than the Goldmann IOPs (p < 0.05) with 60% and 44% of Schiøtz IOPs within ±3 mmHg of the Goldmann tonometer IOP in sessions one and two, respectively. The limits of repeatability and reproducibility were best with the PT-100 and worst with the Schiøtz tonometer. The mean CCT (552±36 µm) was negatively correlated with differences between Goldmann and both PT-100 and Schiøtz-measured IOP.

Conclusion: Postural changes did not affect the validity and repeatability of PT-100 readings. PT-100 measurements were interchangeable with Goldmann tonometer. Schiøtz overestimated Goldmann IOP in thicker corneas more than the PT-100.


Keywords

glaucoma; intraocular pressure; non-contact tonometer; Goldmann applanation tonometer; repeatability; posture

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