Intraocular Pressure Based on Dynamic Bidirectional Applanation and Air-puff Tonometry: A Comparative Study

Area of Science:

• Ophthalmology
• Optometry
• Biomedical Engineering

Background:

• Intraocular pressure (IOP) is a critical metric in diagnosing and managing glaucoma.
• Accurate IOP measurement is essential for effective patient care.
• Different tonometry methods exist, each with potential variations in readings.

Purpose of the Study:

• To compare IOP measurements obtained by dynamic bidirectional applanation (ORA) and air-puff tonometry in healthy eyes.
• To assess the influence of age, gender, spherical equivalent, keratometry, corneal hysteresis (CH), and corneal resistance factor (CRF) on IOP readings.
• To evaluate the agreement between the two tonometry techniques.

Main Methods:

• A cross-sectional retrospective study involving 956 healthy eyes.
• Comparison of IOP measurements from Ocular Response Analyzer (ORA) and air-puff tonometer.
• Univariate and multivariate analyses to investigate correlations with demographic and ocular parameters.
• Bland-Altman plots and intraclass correlation coefficients (r) to assess agreement and reliability.

Main Results:

• Air-puff tonometry yielded higher mean IOP (16.72 ± 2.37 mmHg) compared to ORA (13.75 ± 3.12 mmHg) (p < 0.001).
• Both corneal hysteresis (CH) and corneal resistance factor (CRF) showed significant correlations with IOP measurements from both devices (p < 0.001).
• A low degree of agreement was observed between the two methods (r = 0.443, R² = 0.196).

Conclusions:

• Air-puff tonometry tends to overestimate IOP when compared to ORA.
• The degree of agreement between the two methods is limited.
• Clinical interpretation of air-puff tonometry readings should consider other ophthalmologic findings, and consistent use of the same device is recommended for follow-up.