Comparison of the human and canine Schiotz tonometry conversion tables in clinically normal dogs

Intraocular pressure (IOP) was measured in 114 eyes of 57 clinically normal dogs with 2 applanation tonometers (Tono-Pen and Mackay-Marg) and the Schiotz indentation tonometer, using the 5.5- and 7.5-g weights. Significant differences were not detected between measurements obtained with the Tono-Pen and Mackay-Marg tonometers the Mackay-Marg and Schiotz tonometers using either weight and conversion with the human calibration table, or the Tono-Pen and Schiotz tonometers using the 7.5-g weight and the human calibration table. Values obtained by use of the Tono-Pen tonometer were significantly less (P less than 0.005) than values obtained with the Schiotz tonometer when a 5.5-g weight and the human calibration table were used, but the amount was clinically unimportant. Estimates of IOP using the Schiotz tonometer and the canine calibration table, and either the 5.5- or 7.5-g weight were clinically and significantly much higher (P less than 0.0001) than estimates obtained with the Tono-Pen, Mackay-Marg, or Schiotz tonometers, using the human calibration table and either weight. Sixty to 70% of clinically normal dogs had an IOP greater than or equal to 30 mm of Hg when Schiotz scale measurements were converted with the canine conversion table. For clinically normal dogs, the human calibration table was the most clinically useful table for converting Schiotz tonometer measurements to mm of Hg. Normal mean (+/- SD) canine readings with the Schiotz tonometer and the 5.5-g weight was 4.9 +/- 1.5 tonometer scale units (range, 2 to 11; 95% confidence interval, 1.9 to 7.9).(ABSTRACT TRUNCATED AT 250 WORDS)