Reproducibility of mouse IOP measurements with the rebound tonometer: Performance of a new coil/probe design and software.

Abstract

Abstract: : Purpose: To determine whether a revised coil/probe design and upgraded software of the rebound tonometer improve the ease of use of the instrument while maintaining the same level of reproducibility for non–invasive IOP determination in the mouse. Methods: The prototype rebound tonometer was modified to allow use of a disposable glass sleeve within which the probe moves. In addition the length and mass of the probe was decreased to 19mm and 7.635 (+ 0.063) mg. The software controlling the instrument was modified to allow measurement of IOP from a larger range of starting distances of the probe from the eye to permit hand–held use. The performance of the new design and upgraded software were tested using a calibrator of novel design that simulates the characteristics of the probe impact on the mouse eye. The effect of probe and sleeve variability as well as the effect of starting distance were investigated. The instrument was used to obtain IOP measurements in non–sedated DBA/2 mice of various ages. Results: Reproducibility of the instrument was excellent (SD of 5 individual measurements less than 10% of the mean) for starting probe–eye distances of 2 to 4 mm. Individual probes and glass sleeves contributed little to the instrument variability. Measurements obtained at these starting distances were comparable. IOP measurements in non–sedated mice were readily obtained and confirmed that IOP elevation begins at about 6^th month of age in DBA/2 mice. Conclusions: The new design of the rebound tonometer and the upgraded software offer greater flexibility and ease of use for non–invasive IOP measurements in mice allowing measurements in non–sedated animals.

Keywords: intraocular pressure