Comparisons of the Tono-Pen® and Goldmann Applanation Tonometer in the Measurement of Intraocular Pressure of Primary Open Angle Glaucoma Patients in a Hospital Population in Southwest Nigeria

Abstract

Objective: The aim of this study was to compare intraocular pressure (IOP) measured with the Tono-Pen® to that measured using the Goldmann applanation tonometer (GAT) in patients with primary open angle glaucoma attending a glaucoma clinic. Subjects and Methods: A comparative clinic-based observational study was conducted involving 75 patients (39 men and 36 women) attending a glaucoma clinic in Southwest Nigeria. A pretested structured questionnaire was used to collect sociodemographic data. The Tono-Pen and the GAT were used to measure the IOP in each patient. Central corneal thickness (CCT) was measured with an ultrasonic pachymeter, and the corrected GAT value was calculated for each patient. The Tono-Pen readings were compared with the uncorrected and corrected GAT readings. Descriptive and comparative analyses were performed. Values for p < 0.05 were considered statistically significant. Results: The mean age of the participants was 60.39 ± 16.71 years. The mean IOP using the Tono-Pen was 21.1 ± 6.8 mm Hg versus the mean uncorrected GAT value of 17.1 ± 6.9 mm Hg and the corrected GAT value of 18.9 ± 7.5 mm Hg. The mean CCT was 510.5 ± 29.6 µm. The mean differences between the Tono-Pen reading and uncorrected and corrected GAT readings were 3.9 ± 2.6 and 2.1 ± 3.5 mm Hg, respectively. Gender (Tono-Pen vs. GAT; p = 0.981 vs. 0.437) and corneal thickness (p = 0.057) did not significantly affect the IOP value. Of the 75 patients, 68 (90.7%) preferred the Tono-Pen to the GAT. Conclusion: In this study, the Tono-Pen gave a higher value for IOP than the uncorrected and corrected GAT values. Gender and corneal thickness did not significantly affect the measurements. Most patients found the Tono-Pen more acceptable than the GAT.

Non-contact Tonometry Versus Pachymetry Corrected Intraocular Pressure: Any Difference? A Case for Pachymetry during Glaucoma Screening

“…CCT ranges in Sub-Saharan African countries including Nigeria are yet to be extensively evaluated though a few studies have been done [26][27][28]. In our study the average CCT was 530.2 µm (95% CI, 521.5 -538.7).…”

Changes in Intraocular Pressure with Use of Periocular Triamcinolone Cream

“…[19,20] Our finding that non-applanation measurements with either Tonopen or ICare elevate IOP is also consistent with the literature. [21,22] Topical periocular corticosteroids are currently the treatment of choice for periocular inflammatory conditions such as AD. There is currently no consensus on the risk of IOP elevations from periocular corticosteroid use, which may create uncertainty in providers who wish to initiate therapy.…”

International comparisons of intraocular pressures, as measured by Tono-Pen and Goldmann applanation tonometry, in healthy adults: A meta-analysis

“…[7,22,27,28,30] Variability and inconsistencies reported by TP and GAT comparison studies, which have examined IOP as a function of ocular pathologies, have further contributed to a confused professional literature. Specifically, differences have been reported in IOP, when measured by TP and GAT in patient populations such as glaucoma with varying degrees of severity, [18,24,[31][32][33][34][35] keratoconus, [22,36,37] ocular hypertension, [38] corneal edema, [39,40] as well as patients who have undergone pars plana vitrectomy, [41] endothelial keratoplasty, [42] or penetrating keratoplasty. [39,43] Such studies are useful in understanding IOP as functions of disease processes and surgical procedures; however, these studies fail to provide the necessary normative information required by primary care physicians, charged with initial screenings of potentially debilitating and permanent impairments in vision.…”