Evaluation of differences in Intraocular Pressure (IOP) measurement between Tonoref III and Goldmann Applanation Tonometry (GAT).

Abstract

Purpose : GAT has been the gold standard method for the measurement of IOP for almost 70 years. However, due to its limitations new measurement methods and devices have been developed, such as the non-contact Tonoref III (NIDEK,CO., LTD). There is limited evidence regarding the accuracy of IOP measurements from the new non-contact tonometry device Tonoref III. This study aims to compare IOP measurements between Tonoref III and GAT (AT-900, Haag-Streit).

Methods : We measured IOP on right eyes of two diverse patient groups (over 100 participants each) in this cross-sectional study. To eliminate bias factors, during a single day visitation, IOP measurements from the Tonoref III were recorded first, followed by subsequent measurements using GAT for the 1^st patient group, while the reverse process was implemented for the 2^nd group. The differences between the two groups were assessed using binomial, chi-square and student t-test based on their descriptive and clinical characteristics (such as, gender, age, hypertension etc.). Mean levels of IOP (mean±stand. dev.) and Δ-change of two methods were assessed by Student t and paired samples t-test as well as with the analysis of covariance.

Results : 252 patients included. 132 in the Tonoref III 1^st group (58 males, 74 females; 43.6% and 56.1%, respectively) and 120 in the GAT 1^st group (57 males and 63 females; 47.5% and 52.5%, respectively). No significant difference was found in the distributions of descriptive and clinical characteristics between the two sample groups (p>0.05). IOP measurements with Tonoref III 1^st gave significantly higher mean levels (14.62±3.73mmHg) compared with GAT 2^nd (13.47±3.01) or Δ-change of 1.15±1.96 (p<0.001). Similarly, significantly lower IOP measurements were observed with GAT 1^st (13.85±3.54) and Tonoref III 2^nd (14.32±3.81), or Δ-change of 0.47±2.21 (p=0.020). Nevertheless, the adjusted mean levels of Tonoref III 1^st (14.70; 95% confidence interval: 14.07, 15.28) and GAT 1^st (13.80 95% confidence interval: 13.15, 14.43) measurements had no significant difference (14.68 vs. 13.79mmHg, p=0.051).

Conclusions : Tonoref III seems to provide accurate and reliable measurements, albeit with marginally overestimated IOP compared to conventional GAT measurements. Examiners should consider this difference in their daily IOP screening.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.