A contribution to indirect ophthalmotonometry in beagles

A test of suitability of the electroimpression tonometer from Fritz Schwarzer GmbH, Munich, for measuring intraocular pressure in dogs was performed. Intraocular pressure of 63 clinically healthy English beagles was measured in both eyes using the instrument with different plunger weights. Intraocular pressure and volume of corneal depression during measurement were determined as a function of the plunger weight from readings on the tonometer with the aid of Friedenwald's tables (2). Using Friedenwald's law and with knowledge of the rigidity coefficient, an intraocular pressure of 32.7 mmHg was found, with individual variations between 12.8 and 54.2 mmHg. The rigidity coefficient for dogs, which was determined by linear regression, was, on average, 0.0103. Differences between male and female dogs were not significant for either parameter. A conversion table for eyes with a rigidity factor of 0.0103 is attached. Intraocular pressure as a function of plunger weight and the reading of measurement is shown in mmHg. In our measurements the Schwarzer electrotonometer for determination of intraocular pressure provided easily reproducible readings.