Intraocular Pressure Measurement with Pneumatonometry and a Tonometer Tip Cover During Negative Pressure Application

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Physiology

Background:

• Intraocular pressure (IOP) measurement is critical in diagnosing and managing glaucoma.
• Pneumatonometry is a non-contact method for IOP assessment, but its accuracy under varying negative pressure (NP) conditions requires investigation.
• Perfusion organ culture (POC) models offer a controlled environment to study ocular physiology and instrument performance.

Purpose of the Study:

• To investigate the agreement between pneumatonometry (Excursion tonometry) and direct pressure transducer measurements of IOP.
• To evaluate the impact of negative pressure (NP) on IOP measurements in a POC model.
• To assess the accuracy and reliability of Excursion tonometry in a controlled experimental setting.

Main Methods:

• A two-part study using a perfusion organ culture (POC) model.
• Part 1: Open perfusion fluid column to maintain constant IOP while evaluating NP impact.
• Part 2: Closed system allowing IOP variation with NP application to assess agreement between pneumatonometry and pressure transducer.

Main Results:

• In Part 1 (constant IOP), the mean difference (Δ IOP) between Excursion tonometry and pressure transducer was -0.7 ± 1.6 mmHg.
• In Part 2 (variable IOP), the mean Δ IOP was +0.7 ± 1.4 mmHg.
• Excursion tonometry showed IOP reductions of 3.1 to 11.2 mmHg at NP settings from -5 to -20 mmHg.

Conclusions:

• Excursion tonometry measurements of IOP are within the manufacturer's accuracy range and minimally affected by NP.
• The study supports the effectiveness of Excursion tonometry for IOP assessment in POC models.
• Results are consistent with prior research on IOP reduction techniques.