The validity of a digital eyelid tonometer (TGDc-01) and its comparison with Goldmann applanation tonometry - A pilot study

Purpose: To determine the intra- and inter-examiner repeatability of a new eyelid tonometer, and its agreement with Goldmann applanation tonometry (GAT). Materials and methods: Forty normal subjects were recruited and their intraocular pressure was measured by two examiners using the eyelid tonometer. Examiner 1 carried out the first set of measurement, followed by examiner 2, and then examiner 1 again. Finally, a third examiner was responsible for GAT measurement. Five readings were obtained from the eyelid tonometer by each examiner each time and were masked, and three readings were obtained from GAT. The mean readings from the eyelid tonometer and GAT were used for analysis. Results: The intra-examiner repeatability for the eyelid tonometer was better (around ±5 mmHg 95% of the cases) than the inter-examiner repeatability (around ±8 mmHg 95% of the cases). The mean difference between the eyelid tonometer and GAT was small from examiner 1 (<0.5 mmHg). However, the limits of agreement were greater than the clinically acceptable level of ±3 mmHg. Examiner 2 gave an even greater difference from GAT. Conclusions: Similar to other recent studies, we have found that this eyelid tonometer does not provide good agreement with GAT. Different examiners could position the instrument differently and this eyelid tonometer is suggested for screening purposes only.