A Comparative Study Between the Goldmann Applanation Tonometer and the Non-Contact Air-Puff Tonometer (Huvitz HNT 7000) in Normal Eyes

Abstract

Objective To assess whether the non-contact air-puff tonometer (NCT) is an appropriate alternative to the Goldmann applanation tonometer (GAT) for measuring intraocular pressure (IOP). Patients and Methods An observational, cross-sectional, and comparative study with a quantitative approach was carried out. Two techniques for IOP measurements using the standard GAT and the NCT were compared. A total of 180 eyes from 90 patients were included in the study. Results The total mean IOP according to NCT measurements was 14.12 mmHg, and the total mean IOP according to the GAT was 12.98 mmHg; these values were significantly different (p=0.0018). When dividing the participants into three groups according to the measurement range obtained and comparing the mean NCT and GAT measurements in each group, in Group 1 (10–15 mmHg), no statistically significant difference was found between the means of the two tonometers (p=0.3100), a difference was observed between Group 2 (16–19 mmHg) and Group 3 (20 mmHg or more) (p<0.001). When dividing the participants by age group, the means obtained by the two tonometers also differed significantly between Group 4 (40–59 years) and Group 5 (60 years or more) (p<0.0001). In all groups, the mean measurements by the NCT were higher than those by the GAT. Conclusion The NCT presented an approximate mean of the measures with the GAT in group 1 but was overestimated in the measurements of the groups 2 and 3.

How to Measure Intraocular Pressure: An Updated Review of Various Tonometers

“…Demirci et al showed that IOP measurements with NCT were significantly higher than those obtained with both GAT and rebound tonometry, with significant differences ( p < 0.001) in all age groups [ 36 ]. A recent study confirmed that NCT tends to overestimate IOP GAT measurements in patients with IOP > 16 mmHg, which was more evident when IOP > 20 mmHg [ 37 ], showing a decrease in accuracy at higher values.…”

Comparison of Non-contact Tonometry and Goldmann Applanation Tonometry Measurements in Non-pathologic High Myopia

“…This finding is consistent with that of a previous study, which reported that NCT overestimated IOP in the lower value range and underestimated IOP in the higher value range ( 22 ). However, some studies reported opposite findings, suggesting that IOP NCT values were approximately equal to IOP GAT values in the group with low IOP, while they were overestimated in that with high IOP ( 10 , 23 ). Larger sample sizes are required to validate these results.…”

“…Many types of devices have been proposed for IOP measurement, such as Goldmann applanation tonometry (GAT), non-contact tonometry (NCT), ICare rebound tonometer, and dynamic contour tonometer, each of which has advantages and disadvantages ( 8 ). The GAT is widely regarded as the gold standard for IOP measurement due to its accuracy and excellent reproducibility, while NCT is most widely used in outpatients and in ocular hypertension screening because of its non-invasive and convenient nature ( 9 , 10 ). However, all measurements are influenced by the structure and biomechanical properties of the cornea, such as the cornea thickness and hysteresis, as well as systemic factors such as systolic pressure ( 11 – 13 ).…”

Modalities of Measuring Intraocular Pressure: Updates and Advances

“…At that point, the production of air is stopped, and the force required to flatten is recorded and used to calculate IOP. The disadvantages of the NCT are that it becomes less accurate at higher subject IOPs, especially with IOP > 20 mmHg [33]. It is also influenced by corneal properties, similar to GAT [34].…”