Validation of a New Handheld Automated Fixed-Force Applanation Tonometer

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Medical Devices

Background:

• Intraocular pressure (IOP) measurement is crucial for diagnosing and managing glaucoma.
• Existing tonometry methods have limitations in accuracy and ease of use.
• A novel automated fixed-force applanation tonometer was developed to address these challenges.

Purpose of the Study:

• To validate a novel handheld automated fixed-force applanation tonometer.
• To assess the accuracy of the tonometer using ex vivo human eyes.
• To determine the tonometer's performance across a range of intraocular pressures.

Main Methods:

• A custom tonometer applying constant force was used with a camera to record applanation images.
• Software automatically calculated intraocular pressure (IOP) from the applanation area.
• Ex vivo human eyes were set to IOPs from 5 to 45 mm Hg manometrically, and measurements were compared to set values.

Main Results:

• The novel tonometer demonstrated high accuracy when compared to manometrically set IOPs in ex vivo human eyes.
• Mean absolute difference between measured and set IOP was 3.1 ± 3.5 mm Hg across the full range.
• Accuracy improved significantly in the clinically relevant 10-30 mm Hg range (mean difference 0.7 ± 1.7 mm Hg).
• A strong linear correlation was observed between prototype and set IOP (R² = 0.90, P < 0.0001), improving to R² = 0.95 (P < 0.0001) for 10-30 mm Hg.

Conclusions:

• The novel handheld automated fixed-force applanation tonometer exhibits high accuracy in IOP measurement.
• The device shows particular precision within the 10- to 30-mm Hg IOP range.
• This tonometer has potential applicability for improving patient care in ophthalmology.