Comparison of rebound tonometry and non-contact airpuff tonometry to Goldmann applanation tonometry

Performance of home-based self-tonometry (iCare HOME (TA022)) for measuring intraocular pressure among healthy and glaucoma patients

Introduction: The purpose of this study was to compare iCare HOME (TA022) with Goldmann applanation tonometer and to evaluate the self-tonometry measurements among the Indian population. Methods: Eligible patients underwent iCare HOME training through guided demonstration (verbal, pictorial, video) and practised self-tonometry measures using iCare HOME. Certification for independent iCare HOME measure was provided if first iCare HOME intraocular pressure (IOP) measurement fell within ± 5 mmHg of Goldmann applanation tonometer (GAT) measurement which was measured by the trained clinician (principal investigator). Certified participants underwent simulated home self-tonometry measurements using iCare HOME, and agreement with GAT IOP measurements was assessed. Results: Seven of 83 participants (8.43%) failed to complete the study due to difficulty in performing the task, leading to non-certification. Patients who could use the iCare HOME had a mean age of 53 ± 15.55years (53% males; 46% females). Only one in 12 subjects did not qualify to use iCare HOME. The overall mean difference between iCare HOME and GAT was 0.83 mmHg (95%, 3.92 and -2.25). At various pressure ranges, 7-16 mmHg, 17-23 mmHg and >23 mmHg, the mean difference between iCare HOME and GAT was 1.22 mmHg (95%, 4.32 and -1.86), 0.77 mmHg (95%,3.69 and -2.19), -0.11 mmHg (95%, 2.52 and -2.74) respectively. The intra-class correlation coefficient of the iCare HOME device was 0.997(95% CI,0.995-0.998). Conclusions: Patients were able to perform self- tonometry using iCare HOME with good reliability and safety. iCare HOME can be used to address the issue of difficulty in acquiring frequent and diurnal IOP measurements by patients doing self-tonometry from home.

Agreement among Goldmann Applanation Tonometer, Easyton Transpalpebral Tonometer, Tonopen, and Icare in Patients with Keratoconus

Objectives

The objective of the study is to evaluate the agreement between Goldmann applanation tonometer (GAT) and Easyton transpalpebral tonometer, Tonopen, and Icare in patients with Keratoconus.

Methods

This cross-sectional study included 46 eyes of 26 patients with keratoconus. Intraocular pressure (IOP) is measured using easyton, icare, tonopen, and GAT. Measurements were compared and the influences of corneal topographic variables on IOP measurement were evaluated. Bland-Altman plots were used for assessing agreement between different tonometers.

Results

The mean age of the participants was 24.08±6.76 (range, 18-47) years (15 males and 11 females). The highest of the mean IOP values measured with different tonometers was obtained with Easyton (12.33±1.65), followed by Tonopen (11.59±2.17), GAT (10.67±1.52), and Icare (10.04±2.33). The mean IOP value measured with Easyton was significantly higher than that measured with GAT (p<0.001). There was no significant difference between GAT and either Tonopen (p=0.154) or Icare measurements (p=0.732). There was no significant difference between Tonopen and Easyton measurements (p=0.421). Icare measurements were correlated with central corneal thickness and keratometric values. GAT measurements were correlated with only Kmax. Thirty-eight (82.6%) of the differences were within the agreement limits (assumed clinically important deviation of up to ±2 mmHg) of GAT and Tonopen, 73.9% (n=34) were within the agreement limits of GAT and Icare, and 78.3% (n=36) were within the agreement limits of GAT and Easyton.

Conclusion

Compared with GAT, the gold standard method, Easyton IOP readings were higher, while both Tonopen and Icare readings were similar to GAT. All three tonometers showed acceptable agreement with the GAT, however, Tonopen showed the greatest agreement.

Methods for measuring intraocular pressure: disadvantages and advantages

This review of the literature is devoted to the comparison of tonometers based on various operating principles, their advantages and disadvantages. The principles of operation of each considered in the review tonometer are discussed. The features of the structure and mechanisms for measuring the intraocular pressure of various tonometers are highlighted, on the basis of which the anatomical features and other factors that have the greatest impact on the reliability of measurement and accounting of the data obtained in clinical practice are determined.

Differential impact of prostaglandin analogues on agreement of intraocular pressure measurements obtained by Goldmann applanation, rebound, and noncontact tonometry

Background

To evaluate the effect of topical prostaglandin analogues on agreement of IOP measurements obtained by Goldmann applanation tonometry (GAT), rebound tonometry (RBT), and noncontact tonometry (NCT) in eyes with primary open- angle glaucoma (POAG).

Methods

Intraocular pressure measurements were obtained using GAT, RBT, and NCT in patients with POAG with or without prostaglandin analogues. The agreement between each tonometry was analysed using Bland-Altman analyses in those with or without prostaglandin analogues. The effect of average IOP on IOP differences was also evaluated.

Results

Among a total of 86 subjects included in the study, 44 patients were using prostaglandin analogues. The difference in IOP measured by GAT and RBT was marginally greater in those with (GAT-RBT: − 0.94 ± 1.63 mmHg) prostaglandin analogues than in those without (− 0.33 ± 1.22 mmHg, P = 0.06). The difference in IOP measured by GAT and NCT was significantly greater in the prostaglandin group (GAT-NCT: 2.40 ± 2.89 mmHg) than in the group without prostaglandin analogues (0.41 ± 1.63 mmHg, P < 0.01). While there was no significant relationship between the average of all tonometries and the difference between tonometries in those without prostaglandin analogues, both RBT and NCT underestimated IOP relative to GAT at higher IOP in those using prostaglandin analogues.

Conclusion

Intraocular pressure measured by RBT and NCT was similar to that measured by GAT in those without prostaglandin analogues. RBT overestimated and NCT underestimated IOP compared to GAT in those using prostaglandin analogues.

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

Intraocular pressure (IOP) is an important measurement that needs to be taken during ophthalmic examinations, especially in ocular hypertension subjects, glaucoma patients and in patients with risk factors for developing glaucoma. The gold standard technique in measuring IOP is still Goldmann applanation tonometry (GAT); however, this procedure requires local anesthetics, can be difficult in patients with scarce compliance, surgical patients and children, and is influenced by several corneal parameters. Numerous tonometers have been proposed in the past to address the problems related to GAT. The authors review the various devices currently in use for the measurement of intraocular pressure (IOP), highlighting the main advantages and limits of the various tools. The continuous monitoring of IOP, which is still under evaluation, will be an important step for a more complete and reliable management of patients affected by glaucoma.

Impact of corneal parameters on intraocular pressure measurements in different tonometry methods

AIM

To evaluate the impact of central corneal thickness (CCT) and corneal curvature on intraocular pressure (IOP) measurements performed by three different tonometers.

METHODS

IOP in 132 healthy eyes of 66 participants was measured using three different tonometry techniques: Goldmann applanation tonometer (GAT), Pascal dynamic contour tonometer (DCT), and ICare rebound tonometer (RT). CCT and corneal curvature were assessed.

RESULTS

In healthy eyes, DCT presents significantly higher values of IOP than GAT (17.34±3.69 and 15.27±4.06 mm Hg, P<0.0001). RT measurements are significantly lower than GAT (13.56±4.33 mm Hg, P<0.0001). Compared with GAT, DCT presented on average 2.51 mm Hg higher values in eyes with CCT<600 µm and 0.99 mm Hg higher results in eyes with CCT≥600 µm. The RT results were lower on average by 1.61 and 1.95 mm Hg than those obtained by GAT, respectively. Positive correlations between CCT in eyes with CCT<600 µm were detected for all IOP measurement techniques, whereas a similar relationship was not observed in eyes with thicker corneas. A correlation between IOP values and keratometry in the group with CCT<600 µm was not detected with any of the tonometry methods. In thicker corneas, a positive correlation was found for GAT and mean keratometry values (R=0.369, P=0.005).

CONCLUSION

The same method should always be chosen for routine IOP control, and measurements obtained by different methods cannot be compared. All analysed tonometry methods are dependent on CCT; thus, CCT should be taken into consideration for both diagnostics and monitoring.