Intraocular Pressure Measurements With the Tono-Vera®, a new Handheld Rebound Tonometer.

Abstract

Prcis: In a cross-sectional study comparing the novel Tono-Vera handheld rebound tonometer with the Ocular Response Analyzer, strong agreement was found between intraocular pressure measurements of the two devices.

Purpose: To compare intraocular pressure (IOP) measurements obtained by the new Tono-Vera (Reichert Technologies, Depew, NY), a novel handheld rebound tonometer with proprietary camera-based positioning system, with those from the Ocular Response Analyzer (ORA, Reichert Technologies, Depew, NY) non-contact tonometer.

Patients: 54 eyes of normal individuals and open-angle glaucoma subjects.

Methods: All subjects had at least 6 reliable measurements with the Tono-Vera and 3 with the ORA, acquired by the same technician in the same visit. The sample was randomly split into calibration and validation samples. An ordinary least squares linear regression model generated a calibration formula for Tono-Vera readings using ORA's Goldmann-correlated IOP (IOPg) as target. Bland-Altman plots evaluated agreement between Tono-Vera calibrated IOP (IOPtv) and ORA IOPg in the validation sample.

Main outcome measures: Agreement between IOPtv and IOPg measurements.

Results: 50 glaucoma and 4 normal eyes were included, mean age 68.3 ± 9.4 years, mean central corneal thickness 535.0 ± 39.6 μm. In the validation sample, mean IOPtv was 14.6 ± 5.2 mmHg (range, 7.4-28.5 mmHg) versus 15.0 ± 5.3 mmHg (range, 6.6-28.6 mmHg) for ORA IOPg (R² = 0.782). Bland-Altman plots showed mean difference of -0.4 ± 2.5 mmHg (95% limits of agreement: -5.4 to 4.5 mmHg). 58.6%, 79.3%, and 96.5% of IOPtv measurements fell within ± 2, ± 3, and ± 5 mmHg of ORA measurements. No fixed or proportional biases were observed (P = 0.620).

Conclusion: There was strong correlation and agreement in IOP measurements between calibrated Tono-Vera IOP and ORA IOPg.