Evaluation of Rebound Tonometer for Measuring Intraocular Pressure at Deviated Angle and Position

Purpose: To investigate the influence of positional deviations on the rebound tonometer measurement. Materials and Methods: Ten white rabbits were used. A bottle of balanced salt solution was connected to the anterior chamber, and the IOP was altered by changing the height of the bottle. A pressure transducer was also connected to the anterior chamber. The IOP was measured by the rebound tonometer (RBT), the Tonopen XL, and the Perkins handheld applanation tonometer at optimal conditions and compared each tonometer. Then, the effect of placing the RBT probe at different distances, different lateral positions, and different angles to the cornea on the IOP was determined. Results: The RBT had the lowest variance in all three tonometers. The IOP measured with the RBT was not significantly altered when the distance from the cornea was 4 to 8 mm, or when the probe was displaced 2 mm to the central cornea, or when the probe was placed at an angle of 20 degrees from the central axis. Conclusions: The low variance of the RBT measurements and the non-significant changes in the IOP when the probe of the RBT was not on the central axis indicate that the RBT is useful for animal models of glaucoma. Further studies examining its use (repeatability and reliability) in human infants whose eyes and head are usually moving are required.