Modification and calibration of the Bigliano-Webb Tonometer for improved accuracy of tonometry in rabbits.

The Bigliano-Webb Tonometer (Pneumatonograph) was calibrated for adult and young rabbit eyes using open stopcock and closed stopcock methods. The performance of an old and new instrument were compared illustrating the importance of recent calibration of the instrument for most accurate use. The fact that this tonometer is a high displacement tonometer which requires specific calibration, not only for species but for age of the animal (or size of the eye) is illustrated. A minor modification of the instrument--reducing the setting of a pressure regulator which supplies gas to the tip from its nominal 9 PSI to 2.5 PSI--is illustrated as a method of reducing the difference between intraocular pressure before tonometry and during tonometry, Pt-Po.