Validation of Automated Fixed Force Applanation Tonometry.

PURPOSE: To validate fixed force applanation tonometry against traditional Goldmann applanation tonometry (GAT) and compare interuser reproducibility.

DESIGN

Prospective cross-sectional pilot study.

SUBJECTS: Patients presenting for their routine eye care at an academic glaucoma practice.

METHODS

A prototype adaptor containing a camera was attached to the Goldmann tonometer of a standard slitlamp microscope set to a fixed force in conjunction with a custom tonometer tip. Recorded applanation mires were converted to an intraocular pressure (IOP) using the Imbert-Fick formula. Standard GAT was also performed. Clinical GAT, research GAT, and prototype IOP measurements among different users were also completed.

MAIN OUTCOME MEASURES: Goldmann applanation tonometry and prototype IOPs were compared in a pilot validation study, and interuser reproducibility was assessed using the 2 devices.

RESULTS

In the validation study, 100 eyes from 50 subjects were included. The mean difference between the prototype and standard GAT measurements was +1.0 mmHg, with 95% limits of agreement (LoA) of -3.4 to 5.5 mmHg. The mean absolute difference (± standard deviation) between the prototype IOP and the standard GAT measurement was 1.9 ± 1.5 mmHg. In the reproducibility study, 42 eyes from 21 subjects were included. The mean difference between the research technician prototype IOP and the ophthalmologist prototype IOP measurements was 0.01 mmHg with LoA of -2.5 to 2.4 mmHg. The mean absolute difference between users was significantly lower when using the prototype compared with standard GAT (0.9 ± 1.2 mmHg vs. 1.6 ± 1.1 mmHg, P = 0.003).

CONCLUSIONS

Preliminary measurements using a fixed force applanation tonometry method demonstrated comparable results with standard GAT with improved interuser reproducibility.

FINANCIAL DISCLOSURES: The authors have no proprietary or commercial interest in any materials discussed in this article.