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.
Systemically administered fluorescein is converted to fluorescein glucuronide. The conjugate is fluorescent and interferes with the measurement of fluorescein in the anterior chamber. Carboxyfluorescein is a hydrophilic derivative of fluorescein. In the rabbit, carboxyfluorescein is not converted as readily to a fluorescent metabolite. Thus, carboxyfluorescein has potential advantages as a quantitative fluorophore for studies of aqueous humor dynamics.
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